© 2006 Cisco Systems, Inc. All rights reserved. MPLS v MPLS VPN Implementation Configuring an MP-BGP Session Between PE Routers

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v Outline Overview Configuring BGP Address Families Enabling BGP Neighbors Configuring MP-BGP Configuring MP-IBGP Configuring MP-BGP BGP Community Propagation Disabling IPv4 Route Exchange Summary

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v Configuring BGP Address Families The BGP process in an MPLS VPN-enabled router performs three separate tasks: –Global BGP routes (Internet routing) are exchanged as in traditional BGP setup. –VPNv4 prefixes are exchanged through MP-BGP. –VPN routes are exchanged with CE routers through per- VRF External Border Gateway Protocol sessions. Address families (routing protocol contexts) are used to configure these three tasks in the same BGP process.

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v router bgp as-number Router(config)# Selects global BGP routing process address-family vpnv4 Router(config-router)# Selects configuration of VPNv4 prefix exchanges under MP-BGP sessions address-family ipv4 vrf vrf-name Router(config-router)# Selects configuration of per-VRF PE-CE EBGP parameters Configuring BGP Address Families (Cont.)

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v BGP Neighbors MP-BGP neighbors are configured under the BGP routing process: –These neighbors need to be activated for each global address family that they support. –Per-address-family parameters can be configured for these neighbors. VRF-specific EBGP neighbors are configured under corresponding address families.

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v Configuring MP-BGP MPLS VPN MP-BGP configuration steps: Configure MP-BGP neighbor under BGP routing process. Configure BGP address family VPNv4. Activate configured BGP neighbor for VPNv4 route exchange. Specify additional parameters for VPNv4 route exchange (filters, next hops, and so on).

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v router bgp as-number neighbor ip-address remote-as as-number neighbor ip-address update-source interface-type interface-number Router(config)# All MP-BGP neighbors have to be configured under global BGP routing configuration. MP-IBGP sessions have to run between loopback interfaces. address-family vpnv4 Router(config-router)# This command starts configuration of MP-BGP routing for VPNv4 route exchange. The parameters that apply only to MP-BGP exchange of VPNv4 routes between already configured IBGP neighbors are configured under this address family. Configuring MP-IBGP

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v neighbor ip-address activate Router(config-router-af)# The BGP neighbor defined under BGP router configuration has to be activated for VPNv4 route exchange. neighbor ip-address next-hop-self Router(config-router-af)# The next-hop-self keyword can be configured on the MP-IBGP session for MPLS VPN configuration if EBGP is being run with a CE neighbor. Configuring MP-IBGP (Cont.)

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v neighbor ip-address send-community [standard | extended | both] Router(config-router-af)# This command with the extended option is enabled by default by Cisco IOS software after the BGP neighbor has been activated for VPNv4 route exchange. The command can be used to enable propagation of standard BGP communities attached to VPNv4 prefixes. Usage guidelines: –Extended BGP communities attached to VPNv4 prefixes have to be exchanged between MP-BGP neighbors for proper MPLS VPN operation. –To propagate standard BGP communities between MP BGP neighbors, use the both option. MP-BGP Community Propagation

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v MP-BGP BGP Community Propagation (Cont.)

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v no bgp default ipv4-unicast Router(config-router)# The exchange of IPv4 routes between BGP neighbors is enabled by defaultevery configured neighbor will also receive IPv4 routes. This command disables the default exchange of IPv4 routesneighbors that need to receive IPv4 routes have to be activated for IPv4 route exchange. Use this command when the same router carries Internet and VPNv4 routes and you do not want to propagate Internet routes to some PE neighbors. Disabling IPv4 Route Exchange

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v Neighbor receives only Internet routes. Neighbor receives only VPNv4 routes. Neighbor receives Internet and VPNv4 routes. router bgp no bgp default ipv4-unicast neighbor remote-as neighbor remote-as neighbor remote-as ! Activate IPv4 route exchange neighbor activate neighbor activate ! Step#2 – VPNv4 route exchange address-family vpnv4 neighbor activate neighbor activate Disabling IPv4 Route Exchange (Cont.)

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v Summary Use the address-family command to select the routing context that you want to configure. Use the router bgp command to configure the BGP routing process, and configure VRF-specific EBGP neighbors under corresponding address families. To configure MPLS VPN MP-BGP, you need to: –Configure MP-BGP neighbors. –Configure MP-BGP address family to start VPNv4 routing. –Activate configured MP-BGP neighbors. –Specify additional parameters for VPNv4 route exchange.

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v Summary (Cont.) These commands are used to configure MP-IBGP: –neighbor remote-as –neighbor update-source –neighbor activate –neighbor next-hop-self Use the neighbor send-community command to support standard and extended communities. There are two ways to disable IPv4 route exchange: –no neighbor activate command –no bgp default ipv4-unicast command.

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v