BGP Event-Based VPN Import

The BGP Event-Based VPN Import feature introduces a modification to the existing BGP path import process. BGP Virtual Private Network (VPN) import provides importing functionality for BGP paths where BGP paths are imported from the BGP VPN table into a BGP virtual routing and forwarding (VRF) topology. In the existing path import process, when path updates occur, the import updates are processed during the next scan time which is a configurable interval of 5 to 15 seconds. The scan time adds a delay in the propagation of routes. The enhanced BGP path import is driven by events; when a BGP path changes, all of its imported copies are updated as soon as processing is available.

Using the BGP Event-Based VPN Import feature, convergence times are significantly reduced because provider edge (PE) routers can propagate VPN paths to customer edge (CE) routers without the scan time delay. Configuration changes such as adding imported route-targets to a VRF are not processed immediately, and are still handled during the 60-second periodic scanner pass.

• Import Path Selection Policy
  
• Import Path Limit
  

Perform this task to configure a multiprotocol VRF that allows you to share route-target policies (import and export) between IPv4 and IPv6 or to configure separate route-target policies for IPv4 and IPv6 VPNs. In this task, only the IPv4 address family is configured, but we recommend using the multiprotocol VRF configuration for all new VRF configurations.

Note	This task is not specific to the BGP Event-Based VPN Import feature.

1.    enable

2.    configure terminal

3.    vrf definition vrf-name

4.    rd route-distinguisher

5.    route-target {import | export | both} route-target-ext-community

6.    address-family ipv4 [unicast]

7.    exit-address-family

8.    exit

9.    interface type number

10.    vrf forwarding vrf-name

11.    ip address ip-address mask

12.    no shutdown

13.    exit

14.    Repeat Step 3 through Step 13 to bind other VRF instances with an interface.

15.    end

1.    enable

2.    configure terminal

3.    router bgp autonomous-system-number

4.    address-family ipv4 vrf vrf-name

5.    import path selection {all | bestpath [strict] | multipath [strict]}

6.    import path limit number-of-import-paths

7.    end

1.    enable

2.    show ip bgp vpnv4 {all | rd route-distinguisher | vrf vrf-name} [network-address [mask]]

3.    show ip route [vrf vrf-name] [ip-address [mask]]

4.    debug ip bgp vpnv4 unicast import {events | updates [access-list]}

Router> enable

Router# show ip bgp vpnv4 all 172.17.0.0

BGP routing table entry for 45000:1:172.17.0.0/16, version 10
Paths: (1 available, best #1, table vrf-A)
Flag: 0x820
   Not advertised to any peer
   2, imported safety path from 50000:2:172.17.0.0/16
     10.0.101.1 from 10.0.101.1 (10.0.101.1)
       Origin IGP, metric 200, localpref 100, valid, internal, best
       Extended Community: RT:45000:100

Router# show ip bgp vpnv4 all 172.17.0.0

BBGP routing table entry for 45000:1:172.17.0.0/16, version 11
Paths: (2 available, best #2, table vrf-A)
Flag: 0x820
   Not advertised to any peer
   2
     10.0.101.2 from 10.0.101.2 (10.0.101.2)
       Origin IGP, metric 100, localpref 100, valid, internal, not-in-vrf
       Extended Community: RT:45000:200
       mpls labels in/out nolabel/16
   2
     10.0.101.1 from 10.0.101.1 (10.0.101.1)
       Origin IGP, metric 50, localpref 100, valid, internal, best
       Extended Community: RT:45000:100
       mpls labels in/out nolabel/16

Router# show ip route vrf vrf-A 172.17.0.0

Routing Table: vrf-A
Routing entry for 172.17.0.0/16
  Known via "bgp 1", distance 200, metric 50
  Tag 2, type internal
  Last update from 10.0.101.33 00:00:32 ago
  Routing Descriptor Blocks:
  * 10.0.101.33 (default), from 10.0.101.33, 00:00:32 ago
      Route metric is 50, traffic share count is 1
      AS Hops 1
      Route tag 2
      MPLS label: 16
      MPLS Flags: MPLS Required

Router# debug ip bgp vpnv4 unicast import events

BGP import events debugging is on

In this example configuration, a VRF (vrf-A) is configured and VRF forwarding is applied to Fast Ethernet interface 1/1. In address family mode the import path selection is set to all and the number of import paths is set to 3. Two BGP neighbors are configured under the IPv4 address family and activated under the VPNv4 address family.

vrf definition vrf-A
 rd 45000:1
 route-target import 45000:100
 address-family ipv4
  exit-address-family
!
interface FastEthernet1/1
 no ip address
 vrf forwarding vrf-A
 ip address 10.4.8.149 255.255.255.0
 no shut
 exit
!
router bgp 45000
 network 172.17.1.0 mask 255.255.255.0
 neighbor 192.168.1.2 remote-as 40000
 neighbor 192.168.3.2 remote-as 50000
 address-family ipv4 vrf vrf-A
  import path selection all
  import path limit 3
  exit-address-family
 address-family vpnv4
  neighbor 192.168.1.2 activate
  neighbor 192.168.3.2 activate
  end