In an MPLS VPN configuration, the OSPF protocol is one way you can connect customer edge (CE) routers to service provider edge (PE) routers in the VPN backbone. Sham link configuration example. All VPN processing occurs in the PE router. Enable OSPF routing protocol from global configuration mode. Router2(config-if)# Distributed Denial of Service Attack, BGP NEIGHBORSHIP DROPS WHEN NAT IS ENABLED, VPRN Guide 2021 VIRTUAL PRIVATE ROUTED NETWORK. area method is to set the cost of the forwarding interface on the customer network to be larger than the cost of the sham link. Associates the The "transit area" cannot . For basic information about how to configure an MPLS VPN, refer to the Removes the IP address. Then VPN traffic is transmitted through the route over the backbone network but not backdoor routes. For these steps following commands are used respectively. Across the sham link, the PE routers can build an OSPF adjacency directly with each other. loopback interface to be used as an endpoint of the sham-link on PE-1 and Your software release LSA This prefix is the loopback interface of the Winchester CE router. To reestablish the desired path selection over the MPLS VPN backbone, you must create an additional OSPF intra-area (logical) link between ingress and egress VRFs on the relevant PE routers. number Enters global Copyright 2022 Huawei Technologies Co., Ltd. All rights reserved. specified OSPF process with the VRF associated with the sham-link interface on PWE3 Carrying Enterprise Leased Line Services on a MAN, Licensing Requirements and Limitations for PWE3, (Optional) Creating a PW Template and Setting Attributes for the PW Template, Enabling the Device to Send BFD for PW Packets, Verifying the Configuration of Static BFD for PWs, Verifying the Configuration of Dynamic BFD for PWs, Configuring PW Redundancy in a Scenario Where CEs Are Asymmetrically Connected to PEs, Configuring BFD to Detect Public Network Links, Negotiating the Primary/Secondary Status of a PW, Verifying the PW Redundancy Configuration, Example for Configuring a Dynamic Single-hop PW, Example for Configuring a Static Multi-hop PW, Example for Configuring a Dynamic Multi-hop PW, Example for Configuring a Mixed Multi-hop PW, Example for Configuring Static BFD for PWs, Example for Configuring Dynamic BFD for a Single-hop PW, Example for Configuring Dynamic BFD for a Multi-hop PW, Example for Configuring Inter-AS PWE3-Option A, Example for Configuring PW Redundancy in a Scenario Where CEs Are Asymmetrically Connected to PEs, Interworking Between LDP VPLS and BGP AD VPLS, Licensing Requirements and Limitations for VPLS, Creating a VSI and Configuring LDP Signaling, Enabling the BGP Peer to Exchange VPLS Information, Creating a VSI and Configuring BGP Signaling, (Optional) Configuring Huawei Devices to Communicate with Non-Huawei Devices, (Optional) Configuring the Features of Kompella VPLS, Verifying the Kompella VPLS Configuration, Enabling BGP Peers to Exchange VPLS Information, Creating VSIs and Configuring the BGP AD Signaling, (Optional) Resetting BGP Connections for L2VPN-AD, Configuring Interworking Between LDP VPLS and BGP AD VPLS, Configuring Static VLLs to Access a VPLS Network, Configuring the Static LSP Between the UPE and the SPE, Configuring a UPE to Access an SPE Through a Static VLL, Verifying the Configuration of Static VLLs to Access a VPLS Network, Creating VSIs and Configuring the BGP Signaling, Configuring the Multi-Homed Preference for a VSI, Verifying the Configuration of CE Dual-Homed Kompella VPLS, Configuring Inter-AS Martini VPLS in Option A Mode, Configuring Inter-AS Kompella VPLS in OptionA Mode, (Optional) Associating Spoke PW Status with Hub PW Status, (Optional) Manually Switching PWs in a PW Protection Group, Verifying the VPLS PW Redundancy Configuration, Configuring a VSI to Ignore the AC Status, Configuring VSI-based Traffic Suppression, Verifying the Consistency of VPN Configurations (Service Ping), Verifying the MAC Address Learning Capability, Verifying Connectivity of the VPLS Network, Configuring the Upper and Lower Alarm Thresholds for VPLS VCs, Verifying MPLS L2VPN Specifications and Usage Information, Example for Configuring VPLS over TE in Martini Mode, Example for Configuring VPLS over TE in Kompella Mode, Example for Configuring Interworking Between LDP VPLS and BGP AD VPLS in HVPLS Mode, Example for Configuring Static VLLs to Access a VPLS Network, Example for Configuring Dynamic VLLs to Access a VPLS Network, Example for Configuring CE Dual-Homed Kompella VPLS, Example for Configuring Inter-AS Martini VPLS in OptionA Mode, Example for Configuring Inter-AS Kompella VPLS in OptionA Mode, L2VPN Access to L3VPN Supported by the Switch, Application Scenarios for L2VPN Access to L3VPN, VLL Access to the Public Network or L3VPN, VPLS Access to the Public Network or L3VPN, Licensing Requirements and Limitations for L2VPN Access to L3VPN, Configuring VLL Access to the Public Network or L3VPN, Associating the L2VE Interface with a VLL, Configuring User Access to the Public Network or L3VPN, Verifying the Configuration of VLL Access to the Public Network or L3VPN, Configuring VPLS Access to the Public Network or L3VPN, Verifying the Configuration of VPLS Access to the Public Network or L3VPN, Configuration Examples for L2VPN Access to L3VPN, Example for Configuring VLL Access to L3VPN. No relevant resource is found in the selected language. IGP That is, the VPN traffic 1. How LDP works? MPLS The information displayed on CE1 is used as an example. The sham link is an unnumbered point-to-point link inside a routing-instance between two PE routers. Use Cisco Feature To configure a static route between the PE and the CE routers, include the static statement: content_copy zoom_out_map. VPN The LSA contains information about neighbors and path costs and is used by the receiving router to maintain a routing table. Passive ARPVRRPBackupIP . S1720, S2700, S5700, and S6720 V200R011C10. If the backdoor links between sites are used only for backup purposes and do not participate in the VPN service, then the default route selection shown in the preceding example is not acceptable. In this way, internal OSPF routes that belong to the same VPN and are advertised over the VPN backbone are seen as interarea routes on the remote sites. IP Routing: OSPF Configuration Guide, Cisco IOS Release 15SY, View with Adobe Reader on a variety of devices. Associate the sham-link with an existing OSPF area. If a prefix is learned across the sham-link and the path via the sham-link is selected as the best, the PE router does not generate an MP-BGP update for the prefix. the sham-link on the PE-2 interface within a specified OSPF area and with the Router2(config)# router ospf process-id vrf vrf-name, 18. Navigator to find information about platform support and Cisco software image All VPN processing occurs in the PE router. An Internet protocol used to exchange routing information within an autonomous system. It allows you to create a point-to-point connection between the two PE routers. loopback Enters global On the vManage GUI, click on Configuration => Templates and go to the Feature tab. vrf-name, 12. Figure 75: Network diagram Table 21: Interface and IP address assignment Configuration procedure *> 10.0.0.0 0.0.0.0 0 32768 ? vrf 1. Select vEdge Cloud from the list and choose VPN . Hall of Fame Cisco Employee. Use Cisco Feature !Success rate is 100 percent (5/5), round-trip min/avg/max = 4/46/100 ms, R5(config)#router ospf 1R5(config-router)#network 192.168.50.0 255.0.0.0 area 0R5(config-router)#network 10.0.0.0 0.255.255.255 area 0R5(config-router)#endR3(config)#router ospf 13 vrf A-2R3(config-router)#network 30.0.0.0 0.255.255.255 area 0R3(config-router)#end*Mar 20 00:28:16.623: %OSPF-5-ADJCHG: Process 13, Nbr 192.168.50.1 on FastEthernet0/0 from LOADING to FULL, Loading Done, R3#show ip ospf13neighborNeighbor ID Pri State Dead Time Address Interface192.168.50.1 1 FULL/DR 00:00:33 30.1.1.2 FastEthernet0/0R3#show ip route vrfA-2ospfRouting Table: A-2Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2 i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2 ia - IS-IS inter area, * - candidate default, U - per-user static route o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP + - replicated route, % - next hop overrideGateway of last resort is not set 192.168.50.0/32 is subnetted, 1 subnetsO 192.168.50.1 [110/2] via 30.1.1.2, 00:01:24, FastEthernet0/0, R1(config)#router bgp 6123R1(config-router)#no bgp default ipv4-unicastR1(config-router)#neighbor 192.168.30.1 remote-as 6123R1(config-router)#neighbor 192.168.30.1 update-source loopback 0R1(config-router)#address-family vpnv4 unicastR1(config-router-af)#neighbor 192.168.30.1 activateR1(config-router-af)#neighbor 192.168.30.1 send-community extendedR1(config-router-af)#neighbor 192.168.30.1 next-hop-selfR1(config-router-af)#end, R3(config)#router bgp 6123R3(config-router)#no bgp default ipv4-unicastR3(config-router)#neighbor 192.168.10.1 remote-as 6123R3(config-router)#neighbor 192.168.10.1 update-source loopback 0R3(config-router)#address-family vpnv4 unicastR3(config-router-af)#neighbor 192.168.10.1 activateR3(config-router-af)#neighbor 192.168.10.1 send-community extendedR3(config-router-af)#neighbor 192.168.10.1 next-hop-selfR3(config-router-af)#end, *Mar 20 00:59:36.259: %BGP-5-ADJCHANGE: neighbor 192.168.10.1 Up, R1(config)#router bgp 6123R1(config-router)#address-family ipv4 vrf A-1R1(config-router-af)#redistribute ospf 11 vrf A-1 match ? However, as shown in bold in the next example, the VRF routing table shows that the selected path is learned via OSPF with a next hop of 10.2.1.38, which is the Vienna CE router. PE address To find information about In this way, internal OSPF routes that belong to the same VPN and are advertised over the VPN backbone are seen as inter-area routes on the remote sites. root@R8# run show ospf database instance CE1 OSPF database, Area 0.0.0.0 Type ID Adv Rtr Seq Age Opt Cksum Len Router 172.16.1.1 172.16.1.1 0x80000006 377 0x22 0x5133 72 Router *172.30.5.37 172.30.5.37 0x80000004 2202 0x22 0x3eae 48 . The OSPF intra-area path is preferred over the interarea path (over the MPLS VPN backbone) generated by the PE-1 router. number Configure redistribution on PE routers between OSPF and BGP under VRF. Before you create a sham-link between PE routers in an MPLS VPN, you must: You can use the /32 address for other sham-links. arp broadcast enable ARP. This blog post walks through the problem and the solution, including the configuration steps to create and verify a sham-link. Figure 1: OSPF Sham Link Use the remote-neighbor command to configure the OSPF sham link on both VRFs joined by the link. to avoid loops, ensure that all connected interfaces have STP disabled Each task in the list is identified as either required or optional. Because they can build the OSPF adjacency directly with each other, the routes exchanged between the PE's will remain intra area routes. arp learning passive enable Passive ARPVRRPBackupIPIPARPARP. For the latest After the configuration is complete, PE1 and PE2 can learn the route to the loopback interface of each other and establish an MP-IBGP peer relationship. Associates the The following output shows forwarding information in which the next hop for the route, 10.3.1.2, is the PE-3 router rather than the PE-2 router (which is the best path according to OSPF). Router1(config)# basic bgp configuration # config router bgp set as 65100 set router-id 172.16.1.3 config neighbor edit "10.3.1.254" set remote-as 65200 next end config network edit 1 set prefix 10.1.0.0 255.255.255. protocol redistribution . How LDP works? loopback interface with a VRF. --customer edge router. A VPN client has three sites, each with a backdoor link. A CE router can then learn the routes to other sites in the VPN by peering with its attached PE router. When OSPF routes are propagated over the MPLS VPN backbone, additional information about the prefix in the form of BGP extended communities (route type, domain ID extended communities) is appended to the BGP update. In general, a VRF includes the routing information that defines a customer VPN site that is attached to a PE router. If these sites belong to the same OSPF area, the path over a backdoor link will always be selected because OSPF prefers intraarea paths to interarea paths. sham-links. The PE router also uses the information received from MP-BGP to set the outgoing label stack of incoming packets, and to decide to which egress PE router to label switch the packets. When OSPF is used as a protocol between PE and CE routers, the OSPF metric is preserved when routes are advertised over the VPN backbone. *> 192.168.50.1/32 30.1.1.2 2 32768 ? For the purposes of this documentation set, bias-free is defined as language that does not imply discrimination based on age, disability, gender, racial identity, ethnic identity, sexual orientation, socioeconomic status, and intersectionality. What is MPLS Label distributing protocol (LDP) ? may not support all the features documented in this module. For this reason, you should not modify the metric value when OSPF is redistributed to BGP, and when BGP is redistributed to OSPF. Enters global configuration mode on the second PE router. MPLS When sending traffic to a particular destination, the PE router uses the MP-BGP forwarding information. Router1(config-if)# ip vrf forwarding vrf-name, 6. Sham Link Sham links try to fix a situation where two MPLS VPN sites belong to the same area and have two pathsto each other: MPLS VPN and backdoor link. (PE routers advertise OSPF routes learned over the VPN backbone as interarea paths.) OSPF CEF optimizes network performance and scalability for networks with large and dynamic traffic patterns. In an MPLS VPN configuration, the OSPF cost configured with a sham-link allows you to decide if OSPF client site traffic will be routed over a backdoor link or through the VPN backbone. R4(config-if)#ip address 30.1.1.2 255.0.0.0, R4(config-if)#ip address 192.168.40.1 255.255.255.0, R5(config-if)#Ip address 10.1.1.2 255.0.0.0, R5(config-if)#Ip address 192.168.50.1 255.255.255.0, R1#show ip interface briefInterface IP-Address OK? When OSPF is used to connect PE and CE routers, all routing information learned from a VPN site is placed in the VPN routing and forwarding (VRF) instance associated with the incoming interface. We are using OSPF process 2 inside provider backbone and OSPF process 1 is being used between the CE and PE. loopback interfaces specified by the IP addresses as endpoints. If STP is enabled Configure an OSPF sham link between PE 1 and PE 2 so traffic between the CEs is forwarded through the MPLS backbone instead of the backdoor link. The PE router uses the information received from MP-BGP to set the ongoing label stack of incoming packets, and to decide to which egress PE router to label switch the packets. The reason the OSPF route is not redistributed to BGP on the PE is because the other end of the sham-link already redistributed the route to BGP and there is no need for duplication. cost PE-1 and enters interface configuration mode. The show ip ospf neighbor command can be used to find information about any OSPF neighborships, including the interface, the state, the neighbor's address, and the neighbor's router ID. PE router connected to the CE router collects all the routes in a VRF routing table based on the VRF applied to the incoming interface. No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature. If the twoCEs arent peering over OSPF the only path to reach from CE1 to CE2 is via MPLS VPN backbone. ip Associate the The Sham-link Endpoint Address must be advertised by BGP as VPN-IPv4 address; it must NOT be advertised by OSPF. Two sham-links have been configured, one between PE-1 and PE-2, and another between PE-2 and PE-3. OSPF has a lower administrative distance (AD) than internal BGP (BGP running between routers in the same autonomous system). CE routers are not aware of associated VPNs. We see in the routing table the route for R5s loopback 9.9.0.5 on R1 is received directly from CE2 as intra-area route is preferred over inter-area route. OSPF Sham links is a logical inter-area link carried by the super backbone. router PE Ospf State . forwarding Bug Search Tool and the For example, the figure above shows three client sites, each with backdoor links. which each feature is supported, see the feature information table. router Router1(config-if)# Reconfigures the IP address of the loopback interface on PE-2. When an OSPF sham-link is set it builds a bridge between two VRF's. By advertising a type 1 LSA (Router) across this link, the OSPF database sees this route and the routes advertised across this link as acceptable. VPN Because the sham-link is seen as an intra-area link between PE routers, an OSPF adjacency is created and database exchange (for the particular OSPF process) occurs across the link. The figure below shows an example of how VPN client sites that run OSPF can connect over an MPLS VPN backbone. What they are, how they work, and why we need them. Before you can configure a sham-link in an MPLS VPN, you must first enable OSPF as follows: Specify the range of IP addresses to be associated with the routing process. Router1(config)# --shortest path first calculation. The OSPF intra-area path is preferred over the interarea path (over the MPLS VPN backbone) generated by the PE-1 router. forwarding cost To access Cisco Feature Navigator, go to enters interface configuration mode. second loopback interface with a VRF. configure 2.AS 100IGPOSPF 3.R1-R5MPLS VPN R6-R7MPLS VPN 4.VPN 5.R6 R7OSPFR6-R7MPLS 3. AR1 # interface GigabitEthernet0/0/0 ip address 12.1.1.1 255.255.255. An Internet protocol used to exchange routing information within an autonomous system. To create a sham-link, use the following commands starting in EXEC mode: 2. Perform the following steps on the PE devices at both ends of a sham link. The PE router can then flood LSAs between sites from across the MPLS VPN backbone. When a sham-link is configured between PE routers, the PEs can populate the VRF routing table with the OSPF routes learned over the sham-link. See the following sections for configuration tasks for the sham-link feature. Router1(config-if)# OSPF Sham links are used in MPLS VPNs using OSPF where both sites have a backdoor link and routing preference should be given to the MPLS path instead of backdoor link. Configure VPN instances on PEs and bind the interfaces connected to CEs to the VPN instances. and VLANIF interfaces of switches are used to construct a Layer 3 I am a strong believer of the fact that "learning is a constant process of discovering yourself." the IP address of the loopback interface on PE-2. Some functions of the website may be unavailable. A cost is configured with each sham-link and is used to decide whether traffic will be sent over the backdoor path or the sham-link path. make sure both the CEs routers able to ping. 1 Redistribute external type 1 routes 2 Redistribute external type 2 routes metric Metric for redistributed routes nssa-external Redistribute OSPF NSSA external routes route-map Route map reference R1(config-router-af)#$e ospf 11 vrf A-1 match internal external 1 external 2R1(config-router-af)#end, R1(config)#router ospf 11 vrf A-1R1(config-router)#redistribute bgp 6123subnetsR1(config-router)#end, R3(config)#router bgp 6123R3(config-router)#address-family ipv4 vrf A-2R3(config-router-af)#$e ospf 13 vrf A-2 match internal external 1 external 2R3(config-router-af)#end, (R3(config-router-af)#redistribute ospf 13 vrf A-2 match internal external 1 external 2)R3(config)#router ospf 13 vrf A-2R3(config-router)#redistribute bgp 6123subnetsR3(config-router)#end, BGP table version is 7, local router ID is 192.168.13.1. cost The metric is used on the remote PE routers to select the correct route. Advertise these lo1 addresses in IPV4 BGP as follows: Configure sham-link between PE1 and PE2 using lo1 IP addresses: Note while configuring you will need to ensure the cost of link between CE1 and CE2 always remain higher than that mentioned over Sham-link so that path through sham-link remains the preferred one. --provider edge router. In the following example, PE-2 shows how an MP-BGP update for the prefix is not generated. Configures Within BGP, the locally generated route (10.2.1.38) is considered to be the best route. Examples of common IGPs include IGRP, OSPF, and RIP. ip . Router2# the features documented in this module, and to see a list of the releases in ring network, an interface on the network will be blocked. Configures A VPN contains geographically dispersed sites that can communicate securely over a shared backbone. Forwarding Adjacencies For OSPFv3, OSPF Forwarding Address Suppression in Translated Type-5 LSAs, OSPF Inbound Filtering Using Route Maps with a Distribute List, OSPFv3 Route Filtering Configures the specified OSPF process with the VRF associated with the sham-link interface on PE-1 and enters interface configuration mode. Router1(config)# The following output shows the forwarding that occurs between sites from the standpoint of how PE-1 views the 10.3.1.7/32 prefix, the loopback1 interface of the Winchester CE router in the figure. terminal, 7. This is due to no longer being an external route and becoming an intra-area route. A broadcast packet used by link-state protocols. If these sites belong to the same OSPF area, the path over a backdoor link will always be selected because OSPF prefers intraarea paths to interarea paths. Router2(config)# Cisco IOS software is packaged in feature sets that support specific platforms. *> 30.0.0.0 0.0.0.0 0 32768 ? external Redistribute OSPF external routes internal Redistribute OSPF internal routes nssa-external Redistribute OSPF NSSA external routesR1(config-router-af)#redistribute ospf 11 vrf A-1 match internal ? vrf Step 9: area area-id sham-link source-address destination-address authentication key-chain chain-name. number. www.cisco.com/go/cfn. If no backdoor link exists between the sites, no sham-link is required. Run the display ospf sham-link area command. When a router ID has been found, the process stops. Configure router1 and router 3 in area 0 to ensure that OSPF routes learned other end should prefer MPLS backbone. - Rashmi Bhardwaj (Author/Editor), For Sponsored Posts and Advertisements, kindly reach us at: ipwithease@gmail.com, Routing entry for 9.9.0.5/32Known via ospf 1, distance 110, metric 3, type inter area, Type escape sequence to abort.Tracing the route to 9.9.0.5, Routing entry for 9.9.0.5/32Known via ospf 1, distance 110, metric 2, type intra area, router ospf 1 vrf shamlinkarea 0 sham-link 2.2.2.2 4.4.4.4 cost 1, Sham Link OSPF_SL0 to address 4.4.4.4 is up, BGP routing table entry for 2:2:9.9.0.1/32, version 61, Copyright AAR Technosolutions | Made with in India, How to Replace a vEdge Router via vManage: Cisco Viptela SDWAN, Salesforce Security Best Practices for Keeping Your Data Protected, Technology in the Medical Field to Look Out for in 2023, What is DDoS Attack? configuration mode on the first PE router. area <area-id> sham-link <source-address> <destination-address> cost <cost> from OSPF router configuration mode. Transmitting Multi-Protocol Local Network Data Through a GRE Tunnel, Enlarging the Operation Scope of a Network with a Hop Limit, Building a Virtual Layer 2 Network Using Ethernet over GRE, Using Ethernet over GRE to Enable Layer 2 Communication Between an AC and a Wireless Gateway, Licensing Requirements and Limitations for GRE, Configuring a Route on a Tunnel Interface, (Optional) Configuring a Security Mechanism for GRE, Configuring Basic Ethernet over GRE Functions, (Optional) Configuring Ethernet over GRE Reliability, Collecting and Viewing Statistics on Tunnel Interfaces, Resetting Keepalive Packet Statistics on a Tunnel Interface, Example for Configuring a Static Route for GRE to Implement Interworking Between IPv4 Networks, Example for Configuring OSPF for GRE to Implement Interworking Between IPv4 Networks, Example for Enlarging the Operation Scope of a Network with a Hop Limit, Example for Connecting a CE to a VPN Through a GRE Tunnel over a Public Network, Example for Connecting a CE to a VPN Through a GRE Tunnel over a VPN, Example for Configuring Ethernet over GRE to Build a Virtual Layer 2 Network, Example for Configuring Ethernet over GRE to Enable Layer 2 Communication Between an AC and a Wireless Gateway, The Local Tunnel Interface Fails to Ping the IP Address of the Remote Tunnel Interface, Secure LAN Interconnection Through Efficient VPN, Licensing Requirements and Limitations for IPSec, Configuring an IPSec Session for Encryption, Establishing an IPSec Tunnel Using an Efficient VPN Policy, Verifying the Efficient VPN Configuration, Example for Establishing an IPSec Tunnel Using an Efficient VPN Policy in Client Mode, Example for Configuring an IPSec Tunnel Using an Efficient VPN Policy in Network Mode, Example for Configuring an IPSec Tunnel Using an Efficient VPN Policy in Network-Plus Mode, Application Scenarios for BGP/MPLS IP VPN, Interconnection Between VPNs and the Internet, Summary of BGP/MPLS IP VPN Configuration Tasks, Licensing Requirements and Limitations for BGP/MPLS IP VPN, Configuring Basic BGP/MPLS IP VPN Functions, Summary of Basic BGP/MPLS IP VPN Configuration Tasks, Establishing MP-IBGP Peer Relationships Between PE Devices, Configuring a VPN Instance on a PE Device, Configuring Route Exchange Between PE and CE Devices, Verifying the Configuration of Basic BGP/MPLS IP VPN Functions, Configuring MP-IBGP Between Hub-PE and Spoke-PE, Configuring Route Exchange Between PE device and CE Devices, Verifying the Hub and Spoke Configuration, Configuring Mutual Access Between Local VPNs, (Optional) Enabling Direct ARP Entry Delivery, Verifying the Configuration of Mutual Access Between Local VPNs, Configure Route Exchange Between an MCE Device and VPN Sites, Configure Route Exchange Between an MCE Device and a PE Device, Configuring Route Reflection to Optimize the VPN Backbone Layer, Configuring the Client PEs to Establish MP IBGP Connections with the RR, Configuring the RR to Establish MP IBGP Connections with the Client PEs, Configuring Route Reflection for BGP IPv4 VPN Routes, Verifying the Configuration of Route Reflection to Optimize the VPN Backbone Layer, Configuring and Applying a Tunnel Selector, Verifying Network Connectivity and Reachability, Viewing the Integrated Route Statistics of IPv4 VPN Instances, Resetting BGP Statistics of a VPN Instance IPv4 Address Family, Monitoring the Running Status of VPN Tunnels, Configuration Examples for BGP/MPLS IP VPN, Example for Configuring BGP/MPLS IP VPNs with Overlapping Address Spaces, Example for Configuring Communication Between Local VPNs, Example for Configuring Inter-AS VPN Option A, Example for Configuring an OSPF Sham Link, Example for Configuring BGP AS Number Substitution, Example for Configuring IP FRR for VPN Routes, Example for Configuring IP+VPN Hybrid FRR, Example for Configuring Double RRs to Optimize the VPN Backbone Layer, Example for Connecting a VPN to the Internet, Example for Configuring a Tunnel Policy for an L3VPN, Licensing Requirements and Limitations for BGP/MPLS IPv6 VPN, Summary of Basic BGP/MPLS IPv6 VPN Configuration Tasks, Establishing MP-IBGP Peer Relationships Between PEs, Configuring Route Exchange Between PEs and CEs, Verifying the Configuration of Basic BGP/MPLS IPv6 VPN Functions, Configuring Route Exchange Between the PE and CE, Configuring Route Reflection for BGP VPNv6 Routes, Configuring All Client PEs to Establish IBGP Connections with the RR, Configuring the RR to Establish MP-IBGP Connections with All Client PEs, Configuring Route Reflection for the Routes of the BGP VPN Instance, Verifying the Configuration of Route Reflection for BGP VPNv6 Routes, Monitoring the Running Status of BGP/MPLS IPv6 VPN, Verifying the Network Connectivity and Reachability, Viewing the Integrated Route Statistics of all VPN instances IPv6 address family, Resetting BGP Statistics of VPN instance IPv6 address family, Configuration Examples for BGP/MPLS IPv6 VPN, Example for Configuring Basic BGP/MPLS IPv6 VPN, Example for Configuring Hub and Spoke (Using BGP4+ Between the PE and CE), Example for Configuring Hub and Spoke (Using a Default Route Between Hub-PE and Hub-CE), Example for Configuring Inter-AS IPv6 VPN Option A, Example for Configuring an MCE IPv6 Device, Point-to-Point Layer 2 Connection Between Sites in Different Cities, Multi-service Transparent Transmission over PWs on a MAN, Licensing Requirements and Limitations for VLL, Configuring L2VPN Information Exchange Between the PE Devices, Configuring L2VPN Instances on PE Devices, (Optional) Configuring Route Reflection for BGP L2VPN, (Optional) Configuring Physical Layer Fault Notification, (Optional) Configuring a Revertive Switchover Policy, Enabling the VLL Traffic Statistics Collection Function, Example for Configuring a Local CCC Connection, Example for Configuring a Remote CCC Connection, Example for Configuring a VLL Connection in SVC Mode, Example for Configuring a VLL Connection in Martini Mode, Example for Configuring a Local VLL Connection in Kompella Mode, Example for Configuring a Remote VLL Connection in Kompella Mode, Example for Configuring a VLL Using an MPLS TE Tunnel, Example for Configuring Inter-AS Martini VLL (Option A), Example for Configuring Inter-AS Kompella VLL (Option A), Example for Configuring Martini VLL FRR (Asymmetrically Connected CEs), The VC of a Martini VLL Connection Cannot Go Up. the backbone network. Procedure Configure an endpoint address for the sham link. For basic information about how to configure an MPLS VPN, refer to the "MPLS Virtual Private Networks Configuration" module. Establish an ME-IBGP peer relationship between the PEs and configure OSPF between the PEs and CEs. Sending 5, 100-byte ICMP Echos to 192.168.40.1, timeout is 2 seconds: Success rate is 100 percent (5/5), round-trip min/avg/max = 44/72/104 ms. Sending 5, 100-byte ICMP Echos to 192.168.50.1, timeout is 2 seconds: Success rate is 100 percent (5/5), round-trip min/avg/max = 104/144/248 ms, BGP table version is 7, local router ID is 192.168.33.1, Route Distinguisher: 500:1 (default for vrf A-2). vrf Configures the sham-link on the PE-2 interface within a specified OSPF area and with the loopback interfaces specified by the IP addresses as endpoints. Before you can configure a sham-link in an MPLS VPN, you must first enable OSPF as follows: Specify the range of IP addresses to be associated with the routing process. Router1(config)# interface loopback interface-number, 5. CE R4 (config-router)# redistribute eigrp 1. 2022 Cisco and/or its affiliates. A sham-link between PE-1 and PE-3 is not necessary in this configuration because the Vienna and Winchester sites do not share a backdoor link. An error occurred when loading the video. The following commands are introduced or modified in the feature documented in this module: show If a BGP route and an OSPF route to the same destination are both installed in the IP routing table, OSPF uses the OSPF route because it has a better administrative distance by definition. To locate and download MIBs for selected platforms, Cisco IOS XE releases, and feature sets, use Cisco MIB Locator found at the following URL: Application of the Border Gateway Protocol in the Internet. Figure 1: OSPFv2 Sham Link OSPF has a lower administrative distance (AD) than internal BGP (BGP running between routers in the same autonomous system). The OSPF sham-link is used only to influence intra-area path selection. The syntax to configure sham-link is. In response to Arun Nair. mask, 10. may not support all the features documented in this module. To access Cisco Feature Navigator, go to This community information is used by the receiving PE router to decide the type of link-state advertisement (LSA) to be generated when the BGP route is redistributed to the OSPF PE-CE process. vrf-name, 4. SPF In an MPLS VPN configuration, the OSPF protocol is one way you can connect customer edge (CE) routers to service provider edge (PE) routers in the VPN backbone. The following example shows how to configure a sham-link between two PE routers: BGP Creates a loopback interface to be used as the endpoint of the sham-link on PE-2 and enters interface configuration mode. which each feature is supported, see the feature information table. Unless noted otherwise, subsequent releases of that software release train also support that feature. It is not possible to route traffic from one sham-link over another sham-link. and connected interfaces are removed from VLAN 1. Method Status Protocol, FastEthernet0/0 20.1.1.1 YES manual up up, Serial4/0 1.1.1.2 YES manual up up, Serial4/1 2.2.2.1 YES manual up up, Loopback0 192.168.20.1 YES manual up up, Loopback1 192.168.21.1 YES manual up up, Loopback2 192.168.22.1 YES manual up up, Loopback3 192.168.23.1 YES manual up up, FastEthernet0/0 30.1.1.1 YES manual up up, Serial4/1 2.2.2.2 YES manual up up, Serial4/2 3.3.3.1 YES manual up up, Loopback0 192.168.30.1 YES manual up up, Loopback1 192.168.31.1 YES manual up up, Loopback2 192.168.32.1 YES manual up up, Loopback3 192.168.33.1 YES manual up up, FastEthernet0/0 30.1.1.2 YES manual up up, Loopback0 192.168.40.1 YES manual up up, FastEthernet0/0 10.1.1.2 YES manual up up, Loopback0 192.168.50.1 YES manual up up, R1(config-router)#network 1.0.0.0 0.255.255.255 area 0, R1(config-router)#network 3.0.0.0 0.255.255.255 area 0, R1(config-router)#network 192.168.10.0 255.0.0.0 area 0, R1(config-router)#network 192.168.11.0 255.0.0.0 area 0, R1(config-router)#network 192.168.12.0 255.0.0.0 area 0, R1(config-router)#network 192.168.13.0 255.0.0.0 area 0, R2(config-router)#network 20.0.0.0 0.255.255.255 area 0, R2(config-router)#network 1.0.0.0 0.255.255.255 area 0, R2(config-router)#network 2.0.0.0 0.255.255.255 area 0, R2(config-router)#network 192.168.20.0 255.0.0.0 area 0, R2(config-router)#network 192.168.21.0 255.0.0.0 area 0, R2(config-router)#network 192.168.22.0 255.0.0.0 area 0, R2(config-router)#network 192.168.23.0 255.0.0.0 area 0, R3(config-router)#network 2.0.0.0 0.255.255.255 area 0, R3(config-router)#network 3.0.0.0 0.255.255.255 area 0, R3(config-router)#network 192.168.30.0 255.0.0.0 area 0, R3(config-router)#network 192.168.31.0 255.0.0.0 area 0, R3(config-router)#network 192.168.32.0 255.0.0.0 area 0, R3(config-router)#network 192.168.33.0 255.0.0.0 area 0, Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP, D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area, N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2, E1 - OSPF external type 1, E2 - OSPF external type 2, i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area, * - candidate default, U - per-user static route, o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP, + - replicated route, % - next hop override, O 2.0.0.0/8 [110/128] via 3.3.3.1, 01:14:38, Serial4/2, [110/128] via 1.1.1.2, 01:14:38, Serial4/0, O 20.0.0.0/8 [110/65] via 1.1.1.2, 01:14:38, Serial4/0, O 192.168.20.1 [110/65] via 1.1.1.2, 01:14:38, Serial4/0, O 192.168.21.1 [110/65] via 1.1.1.2, 01:14:38, Serial4/0, O 192.168.22.1 [110/65] via 1.1.1.2, 01:14:38, Serial4/0, O 192.168.23.1 [110/65] via 1.1.1.2, 01:14:38, Serial4/0, O 192.168.30.0/24 [110/65] via 3.3.3.1, 01:14:38, Serial4/2, O 192.168.31.1 [110/65] via 3.3.3.1, 01:14:38, Serial4/2, O 192.168.32.1 [110/65] via 3.3.3.1, 01:14:38, Serial4/2, O 192.168.33.1 [110/65] via 3.3.3.1, 01:14:38, Serial4/2, O 1.0.0.0/8 [110/128] via 3.3.3.2, 01:18:05, Serial4/2, [110/128] via 2.2.2.1, 01:18:05, Serial4/1, O 20.0.0.0/8 [110/65] via 2.2.2.1, 01:18:05, Serial4/1, O 192.168.10.0/24 [110/65] via 3.3.3.2, 01:18:05, Serial4/2, O 192.168.11.1 [110/65] via 3.3.3.2, 01:18:05, Serial4/2, O 192.168.12.1 [110/65] via 3.3.3.2, 01:18:05, Serial4/2, O 192.168.13.1 [110/65] via 3.3.3.2, 01:18:05, Serial4/2, O 192.168.20.1 [110/65] via 2.2.2.1, 01:18:05, Serial4/1, O 192.168.21.1 [110/65] via 2.2.2.1, 01:18:05, Serial4/1, O 192.168.22.1 [110/65] via 2.2.2.1, 01:18:05, Serial4/1, O 192.168.23.1 [110/65] via 2.2.2.1, 01:18:05, Serial4/1, R1(config)#mpls label protocol ldpR1(config)#mpls label range 99 199R1(config)#mpls ldp router-id loopback 0R1(config)#exitR1(config)#interface serial 4/0R1(config-if)#mpls ipR1(config-if)#exitR1(config)#interface serial 4/2R1(config-if)#mpls ipR1(config-if)#exit, R2(config)#mpls label protocol ldpR2(config)#mpls label range 200 299R2(config)#mpls ldp router-id loopback 0R2(config)#exitR2(config)#interface serial 4/0R2(config-if)#mpls ipR2(config-if)#exitR2(config)#interface serial 4/1R2(config-if)#mpls ipR2(config-if)#exitR3(config)#mpls label protocol ldpR3(config)#mpls label range 300 399R3(config)#mpls ldp router-id loopback 0R3(config)#exit, R3(config)#interface serial 4/1R3(config-if)#mpls ipR3(config-if)#exitR3(config)#interface serial 4/2R3(config-if)#mpls ipR3(config-if)#exit, R1#show mpls ldp neighbor Peer LDP Ident: 192.168.20.1:0;Local LDP Ident 192.168.10.1:0 TCP connection: 192.168.20.1.41723 - 192.168.10.1.646 State: Oper; Msgs sent/rcvd: 190/188; Downstream Up time: 02:23:12 LDP discovery sources: Serial4/0, Src IP addr: 1.1.1.2 Addresses bound to peer LDP Ident: 20.1.1.1 1.1.1.2 2.2.2.1 192.168.20.1 192.168.21.1 192.168.22.1 192.168.23.1 Peer LDP Ident: 192.168.30.1:0;Local LDP Ident 192.168.10.1:0 TCP connection: 192.168.30.1.27403 - 192.168.10.1.646 State: Oper; Msgs sent/rcvd: 186/184; Downstream Up time: 02:20:31 LDP discovery sources: Serial4/2, Src IP addr: 3.3.3.1 Addresses bound to peer LDP Ident: 2.2.2.2 3.3.3.1 192.168.30.1 192.168.31.1 192.168.32.1 192.168.33.1, Peer LDP Ident: 192.168.10.1:0; Local LDP Ident 192.168.20.1:0, TCP connection: 192.168.10.1.646 - 192.168.20.1.41723, State: Oper; Msgs sent/rcvd: 189/192; Downstream, 1.1.1.1 3.3.3.2 192.168.10.1 192.168.11.1, Peer LDP Ident: 192.168.30.1:0; Local LDP Ident 192.168.20.1:0, TCP connection: 192.168.30.1.64637 - 192.168.20.1.646, State: Oper; Msgs sent/rcvd: 187/189; Downstream, 2.2.2.2 3.3.3.1 192.168.30.1 192.168.31.1, Peer LDP Ident: 192.168.20.1:0;Local LDP Ident 192.168.30.1:0, TCP connection: 192.168.20.1.646 - 192.168.30.1.64637, State: Oper; Msgs sent/rcvd: 190/188; Downstream, 20.1.1.1 1.1.1.2 2.2.2.1 192.168.20.1, 192.168.21.1 192.168.22.1 192.168.23.1, Peer LDP Ident: 192.168.10.1:0; Local LDP Ident 192.168.30.1:0, TCP connection: 192.168.10.1.646 - 192.168.30.1.27403, % Interface FastEthernet0/0 IPv4 disabled and address(es) removed due to enabling VRF A-1, R1(config-if)#ip address 10.1.1.1 255.0.0.0, % Interface FastEthernet0/0 IPv4 disabled and address(es) removed due to enabling VRF A-2, R3(config-if)#ip address 30.1.1.1 255.0.0.0, R1#show run | section vrfip vrf A-1rd 500:1route-target export 500:1route-target import 500:1ip vrf forwarding A-1, R1(config)#interface loopback 0R1(config-if)#ip ospf network point-to-pointR1(config-if)#end, R3(config)#interface loopback 0R3(config-if)#ip ospf network point-to-pointR3(config-if)#end, R4(config)#router ospf 1R4(config-router)#network 192.168.40.0 255.0.0.0 area 0R4(config-router)#network 30.0.0.0 0.255.255.255 area 0R4(config-router)#end, R1(config-router)#network 10.0.0.0 0.255.255.255 area 0, *Mar 20 00:18:20.379: %OSPF-5-ADJCHG: Process 11, Nbr 192.168.40.1 on FastEthernet0/0 from LOADING to FULL, Loading Done, Neighbor ID Pri State Dead Time Address Interface, 192.168.33.1 0 FULL/ - 00:00:33 3.3.3.1 Serial4/2, 192.168.23.1 0 FULL/ - 00:00:38 1.1.1.2 Serial4/0, 192.168.40.1 1 FULL/DR 00:00:33 10.1.1.2 FastEthernet0/0, O 192.168.40.1 [110/2] via 10.1.1.2, 00:01:43, FastEthernet0/0, R1#ping vrf A-1 192.168.40.1Type escape sequence to abort.Sending 5, 100-byte ICMP Echos to 192.168.40.1, timeout is 2 seconds:!!!! Interdomain routing protocol that exchanges reachability information with other BGP systems. Sham Linkcan be created using two loopbacks on the respective devices advertised into the BGP address family that corresponds with the customerVRF. A sham-link is required between any two VPN sites that belong to the same OSPF area and share an OSPF backdoor link. Figure 1 shows an OSPFv2 sham link. ip address Reconfigures --Interior Gateway Protocol. How LDP works? *> 192.168.40.1/32 10.1.1.2 2 32768 ? To obtain lists of supported MIBs by platform and Cisco IOS release, and to download MIB modules, go to the Cisco MIB website on Cisco.com at the following URL: http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml. The following example shows the forwarding that occurs between sites from the standpoint of how PE-1 views the 10.3.1.7/32 prefix, the loopback1 interface of the Winchester CE router in the figure above. The following example shows how to configure a sham-link between two PE routers: The following sections provide references related to the OSPF Sham-Link Support for MPLS VPN feature. Two sham-links have been configured, one between PE-1 and PE-2, and another between PE-2 and PE-3. 9.How to configure MPLS L3 with BGP AS OVERRIDE? Glimpse of "EIGRP name mode configuration", Understanding Wireless Client Authentication, configure the topology as per the diagram, assign the IP addresses to their interfaces, configure IGP (OSPF 1) inside MPLS SP core, configure labels (99-199_200-299_300-399), configure VRF A-1 on router 1 and VRF A-2 on router 3, configure RD and RT value 500:1 on both the sites, configure on router 1 assign fastethernet facing CE under VRF A-1, configure on router 3 assign fastethernet facing CE under VRF A-2, Configure the loopbacks with exact mask to exchange the routes, configure OSPF 11 on PE router 1 under VRF A-1 and OSPF 13 on PE router 3 under VRF A-2. When OSPF is used as a protocol between PE and CE routers, the OSPF metric is preserved when routes are advertised over the VPN backbone. Keep this in mindyou need to configure the OSPF router ID and NOT the IP address of the ABR. Try to reboot to see whether they change. Under the release section, you can compare releases side by side to display both the features unique to each software release and the features in common. OSPF STATE STUCK MTU MISMATCH. Cost of using 1 State POINT_TO_POINT. A secure IP-based network that shares resources on one or more physical networks. address for other sham-links. Router2(config-if)# area area-id sham-link source-address destination-address cost number. the sham-link on the PE-1 interface within a specified OSPF area and with the how to configure OSPF Sham Links? We configure the virtual-link between ABRs and we use the area virtual-link command. The MPLS VPN superbackbone provides an additional level of routing hierarchy to interconnect the VPN sites running OSPF. When the backdoor link is not enabled between the CE1 and CE2 the path followed from CE1 to CE2 is via MPLS backbone as shown below , Last update from 9.9.12.2 on FastEthernet0/0, 00:00:10 ago, * 9.9.12.2, from 9.9.12.2, 00:00:10 ago, via FastEthernet0/0 #Known via R2#, Route metric is 3, traffic share count is 1, VRF info: (vrf in name/id, vrf out name/id), 2 9.9.23.3 [MPLS: Labels 17/16 Exp 0] 96 msec 56 msec 76 msec, 3 9.9.45.4 [MPLS: Label 16 Exp 0] 84 msec 80 msec 56 msec. These routes are then propagated across other PEs using MP-BGP. Timer intervals configured, Hello 10, Dead 40, Wait 40, Index 2/2, retransmission queue length 0, number of retransmission 0, Last retransmission scan length is 0, maximum is 0, Last retransmission scan time is 0 msec, maximum is 0 msec, Sham Link OSPF_SL0 to address 111.5.5.5 is up. CEF # rip 1 version 2 network 192.168.1. network 12.0.0.0 AR2 ip vpn-instance a Reconfigures the IP address of the loopback interface on PE-1. To begin, MPLS is set up in the network as shown with R2 and R4 acting as Provider Edge (PE) routers, and MPLS is enabled throughout R2-R3-R4. A router that is part of a service provider network connected to a customer edge (CE) router. Device(config-router-af)# area 1 virtual-link 1.1.1.1 authentication key-chain ospf-chain-1: Configures the authentication for virtual links. cost number configures the OSPF cost for sending an IP packet on the PE-1 sham-link interface. Run the tracert command on CE1. Complete basic BGP/MPLS IP VPN configuration on the backbone network: configure an IGP, enable MPLS and LDP, and establish an MP-IBGP peer relationship between the PEs. --Interior Gateway Protocol. Creates a --Open Shortest Path First protocol. Customers Also Viewed These Support Documents. The example in this section is designed to show how a sham-link is used only to affect the OSPF intra-area path selection of the PE and CE routers. lets see the configuration for better understanding:-, R1(config-if)#Ip address 10.1.1.1 255.0.0.0, R1(config-if)#Ip address 1.1.1.1 255.0.0.0, R1(config-if)#Ip address 3.3.3.2 255.0.0.0, R1(config-if)#Ip address 192.168.10.1 255.255.255.0, R1(config-if)#Ip address 192.168.11.1 255.255.255.0, R1(config-if)#Ip address 192.168.12.1 255.255.255.0, R1(config-if)#Ip address 192.168.13.1 255.255.255.0, R2(config-if)#Ip address 20.1.1.1 255.0.0.0, R2(config-if)#Ip address 1.1.1.2 255.0.0.0, R2(config-if)#Ip address 2.2.2.1 255.0.0.0, R2(config-if)#Ip address 192.168.20.1 255.255.255.0, R2(config-if)#Ip address 192.168.21.1 255.255.255.0, R2(config-if)#Ip address 192.168.22.1 255.255.255.0, R2(config-if)#Ip address 192.168.23.1 255.255, R3(config-if)#Ip address 30.1.1.1 255.0.0.0, R3(config-if)#Ip address 2.2.2.2 255.0.0.0, R3(config-if)#Ip address 3.3.3.1 255.0.0.0, R3(config-if)#Ip address 192.168.30.1 255.255.255.0, R3(config-if)#Ip address 192.168.31.1 255.255.255.0, R3(config-if)#Ip address 192.168.32.1 255.255.255.0. Configuration for IOS XE and IOS XR as below IOS XE Sham-Link Configuration router ospf 100 vrf A The OSPF costs Configure VPN instances on PEs and bind the interfaces connected to CEs to the VPN instances. The metric is used on the remote PE routers to select the correct route. Version:V200R020C10.null. First you need to specify the area 1 where we need the virtual-link which is area 1 in my example. For this reason, OSPF backdoor links between VPN sites must be taken into account so that routing is performed based on policy. Areaarea-idsham-linksource-address destination-addresscostnumber. Examples of common IGPs include IGRP, OSPF, and RIP. All rights reserved. The documentation set for this product strives to use bias-free language. OSPF adjacency is established across the sham link. OSPF sham-links correct this behavior. Router1(config-if)# ip address ip-address mask, 10. Timer intervals configured, Hello 10, Dead 40, Wait 40, Index 2/2, retransmission queue length 0, number of retransmission 0, Last retransmission scan length is 0, maximum is 0, Last retransmission scan time is 0 msec, maximum is 0 msec, Paths: (1 available, best #1, table shamlink), Origin incomplete, metric 2, localpref 100, weight 32768, valid, sourced, best, Extended Community: RT:2:1OSPF DOMAIN ID:0x0005:0x000000010200, OSPF RT:0.0.0.0:2:0 OSPF ROUTER ID:9.9.12.2:0, 2 9.9.23.3 [MPLS: Labels 17/27 Exp 0] 84 msec 44 msec 68 msec, 3 9.9.45.4 [MPLS: Label 27 Exp 0] 68 msec 28 msec 68 msec, Known via ospf 1, distance 110, metric 4, type intra area, Last update from 9.9.12.2 on FastEthernet0/0, 00:00:56 ago, * 9.9.12.2, from 9.9.0.5, 00:00:56 ago, via FastEthernet0/0Known via R2#, Route metric is 4, traffic share count is 1, OSPF Multi-Area Adjacency : Example Scenario, I am here to share my knowledge and experience in the field of networking with the goal being - "The more you share, the more you learn." To verify that the sham-link was successfully created and is operational, use the show ip ospf sham-links command in EXEC mode: Displays the operational status of all sham-links configured for a router. This video demonstrates configuration a DMVPN Hub and Spoke in Phase 3 Configuration.It confirms Phase 3 connectivity between 2 Spokes and Hub to Spoke Conf. --Multiprotocol Label Switching. OSPF adjacency is established across the sham link. VRF terminal, 2. --shortest path first calculation. Cisco Express Forwarding. Pre-configuration Tasks. The section, "Creating a Sham-Link", describes how to configure a sham-link between two PE routers. The Sham-link is an unnumbered point-to-point intra-area link and is advertised as . 10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks, C 10.0.0.0/8 is directly connected, FastEthernet0/0, L 10.1.1.1/32 is directly connected, FastEthernet0/0, B 30.0.0.0/8 [200/0] via 192.168.30.1, 00:05:57, O 192.168.40.1 [110/2] via 10.1.1.2, 00:40:55, FastEthernet0/0, B 192.168.50.1 [200/2] via 192.168.30.1, 00:05:57, B 30.0.0.0/8 [200/0] via 192.168.30.1, 00:06:24, B 192.168.50.1 [200/2] via 192.168.30.1, 00:06:24. This community information is used by the receiving PE router to decide the type of link-state advertisement (LSA) to be generated when the BGP route is redistributed to theOSPF PE-CEprocess. Associates the loopback interface with a VRF. --VPN routing and forwarding instance. support. Cisco Feature Navigator dynamically updates the list of supported platforms as new platform support is added for the feature. When a sham-link is configured between PE routers, the PEs can populate the VRF routing table with the OSPF routes learned over the sham-link. The reason the OSPF route is not redistributed to BGP on the PE is because the other end of the sham-link already redistributed the route to BGP and there is no need for duplication. To select a router ID for OSPF, a router goes through a process. Router2(config)# interface loopback interface-number, 11. router process-id Bug Search Tool and the Router CE1 and Router CE2 are located in the same OSPFv2 area. destination of the sham link. Configure OSPF on CE1, Switch, and CE2 and advertise the network segment of each interface. As shown in bold in this example, the loopback interface is learned via BGP from PE-2 and PE-3. In some cases where Providers deliverMPLSlinks to customer locations ,OSPFmay be used asCE-PErouting protocol. Exceptions may be present in the documentation due to language that is hardcoded in the user interfaces of the product software, language used based on RFP documentation, or language that is used by a referenced third-party product. For this reason, you should not modify the metric value when OSPF is redistributed to BGP, and when BGP is redistributed to OSPF. What is MPLS Label distributing protocol (LDP) ? sham-link with an existing OSPF area. The command output shows that the routes to the remote CEs are OSPF routes through the customer network, not the BGP routes through ip-address configure VPNv4 peering between PE routers. R3(config-if)#Ip address 192.168.33.1 255.255. All rights reserved. In an MPLS VPN configuration, the OSPF cost configured with a sham-link allows you to decide if OSPF client site traffic will be routed over a backdoor link or through the VPN backbone. on PE-2 and enters interface configuration mode. Navigator to find information about platform support and Cisco software image Before you create a sham-link A CE router can then learn the routes to other sites in the VPN by peering with its attached PE router. ip Cisco IOS IP Routing: OSPF Command Reference, Cisco IOS master command list, all releases, Cisco IOS Master Command List, All Releases. A sham-link is required between any two VPN sites that belong to the same OSPF area and share an OSPF backdoor link. Last update from 9.9.15.5 on FastEthernet1/0, 00:00:01 ago, * 9.9.15.5, from 9.9.0.5, 00:00:01 ago, via FastEthernet1/0 #Known VIA R5 now#, Route metric is 2, traffic share count is 1. The following example shows BGP routing table entries for the prefix 10.3.1.7/32 in the PE-1 router in the figure above. If the backdoor links between sites are used only for backup purposes and do not participate in the VPN service, then the default route selection shown in the preceding example is not acceptable. sham-linksource-address sham-link between PE routers in an MPLS VPN, you must: You can use the /32 For this reason, OSPF backdoor links between VPN sites must be taken into account so that routing is performed based on policy. As shown in bold in this example, the loopback interface is learned via BGP from PE-2 and PE-3. ip release notes for your platform and software release. Table 1Feature Information for OSPF Sham-Link Support for MPLS VPN, IPv6 Routing: OSPFv3 Authentication Support with IPsec, OSPF Update Packet-Pacing Configurable Timers, Autoroute Announce and When the backbone network is running properly, VPN traffic of CE1 and CE2 should be forwarded over the MPLS backbone network without passing through the OSPF intra-area routes. Introduction of MPLS 2. No new or modified RFCs are supported by this feature. Interdomain routing protocol that exchanges reachability information with other BGP systems. Emerging industry standard upon which tag switching is based. external Redistribute OSPF external routes metric Metric for redistributed routes nssa-external Redistribute OSPF NSSA external routes route-map Route map reference R1(config-router-af)#redistribute ospf 11 vrf A-1 match internal external ? Using Distribute-List, OSPF Limit on Number of Redistributed Routes, OSPFv3 Fast Convergence: LSA and SPF Throttling, OSPF Support for Unlimited Software VRFs per PE Router, OSPF Link-State Database Overload Protection, OSPF MIB Support of RFC 1850 and Latest Extensions, Configuring OSPF TTL Security Check and OSPF Graceful Shutdown, OSPF SNMP ifIndex Value for Interface ID in Data Fields, OSPF Support for Forwarding Adjacencies over MPLS TE Tunnels, OSPF IPv4 Remote Loop-Free Alternate IP Fast Reroute, Prerequisites for OSPF Sham-Link Support for MPLS VPN, Restrictions on OSPF Sham-Link Support for MPLS VPN, Information About OSPF Sham-Link Support for MPLS VPN, Benefits of OSPF Sham-Link Support for MPLS VPN, Using a Sham-Link to Correct OSPF Backdoor Routing, Configuration Examples of an OSPF Sham-Link, Example Sham-Link Between Two PE Routers, Feature Information for OSPF Sham-Link Support for MPLS VPN. Creating the VPN Interface Template for the TLOC-EXT interface. A Sham links is required only between two VPN sites that belong to the same area and have a backdoor link for backup purposes. This community information is used by the receiving PE router to decide the type of link-state advertisement (LSA) to be generated when the BGP route is redistributed to the OSPF PE-CE process. interface. To obtain better user experience, upgrade the browser to the latest version. support. After entering these commands we will see a warning from R4. You can change lines. A cost is configured with each sham-link and is used to decide whether traffic will be sent over the backdoor path or the sham-link path. How to configure MPLS L3 with BGP AS OVERRIDE? It is defined in RFC 1163. In addition, Router CE1 and Router CE2 are connected by an intra-area link used as a backup. For the latest When OSPF routes are propagated over theMPLS VPNbackbone, additional information about the prefix in the form of BGP extended communities (route type, domain ID extended communities) is appended to the BGP update. Set the cost value of the forwarding interface of the private network to be larger than the cost of the sham link so that VPN traffic is transmitted over the MPLS backbone network. An account on Cisco.com is not required. For more information about how to configure OSPF, refer to the "Configuring OSPF" module. Further, routes reach the remote CE after being redistributed from BGP into OSPF process running between CE and PE for a specific VRF. If a prefix is learned across the sham-link and the path via the sham-link is selected as the best, the PE router does not generate an MP-BGP update for the prefix. The command output shows that the neighbor relationship is in Full state. router BGP Configure one serial link (backup link /backdoor) between router 4/5. *>i192.168.40.1/32 192.168.10.1 2 100 0 ? The figure below shows a sample sham-link between PE-1 and PE-2. Router2(config-if)# VPN traffic between CE 1 and CE 2 is required to be forwarded through the MPLS backbone, instead of any route in the OSPF area. Reconfigures OSPF is often used by customers who run OSPF as their intrasite routing protocol, subscribe to a VPN service, and want to exchange routing information between their sites using OSPF (during migration or on a permanent basis) over an MPLS VPN backbone. *>i 10.0.0.0 192.168.10.1 0 100 0 ? Method Status ProtocolFastEthernet0/0 10.1.1.1 YES manual up upSerial4/0 1.1.1.1 YES manual up upSerial4/2 3.3.3.2 YES manual up upLoopback0 192.168.10.1 YES manual up upLoopback1 192.168.11.1 YES manual up upLoopback2 192.168.12.1 YES manual up upLoopback3 192.168.13.1 YES manual up up, Interface IP-Address OK? The CEs and PEs need to run OSPF. Sham link must be configured on both sides. Although OSPF PE-CE connections assume that the only path between two client sites is across the MPLS VPN backbone, backdoor paths between VPN sites (shown in grey in the figure below) may exist. Because each site runs OSPF within the same Area 1 configuration, all routing between the three sites follows the intraarea path across the backdoor links, rather than over the MPLS VPN backbone. process-id This module describes how to configure and use a sham-link to connect Virtual Private Network (VPN) client sites that run the Open Shortest Path First (OSPF) protocol and share backdoor OSPF links in a Multiprotocol Label Switching (MPLS) VPN configuration. A sham-link ensures that OSPF client sites that share a backdoor link can communicate over the MPLS VPN backbone and participate in VPN services. Peter Paluch. r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter. Layer 3 services on the network cannot run normally. ospf the IP address of the loopback interface on PE-1. These customer edge (CE) routing devices are linked together by a Layer 3 VPN over Router PE1 and Router PE2. before adding sham-link. This example is designed to show how a sham-link is used only to affect the OSPF intra-area path selection of the PE and CE routers. For a sham link to be active, two conditions must be met: src-address is a valid local address with /32 netmask in OSPF instance's routing table. As a result, the desired intra-area connectivity is created. 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