OS10 Enterprise Edition User Guide Release 10.4.0E(R3)

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Neighbor fall-over

The BGP neighbor fall-over feature reduces the convergence time while maintaining stability. When you enable fall-over, BGP tracks IP reachability to the peer remote address and the peer local address.

When remote or peer local addresses become unreachable, BGP brings the session down with the peer. For example, if no active route exists in the routing table for peer IPv6 destinations/local address, BGP brings the session down.

By default, the hold time governs a BGP session. Configure BGP fast fall-over on a per-neighbor or peer-group basis. BGP routers typically carry large routing tables as frequent session resets are not desirable. If fail-over is enabled, the connection to an internal BGP peer is immediately reset if the host route added to reach the internal peer fails.

  1. Enter the neighbor IP address in ROUTER-BGP mode.
    neighbor 
                                           ip-address
                                        
  2. Disable fast fall-over in ROUTER-NEIGHBOR mode.
    no fall-over
  3. Enter the neighbor IP address in ROUTER-BGP mode.
    neighbor 
                                           ip-address
                                        
  4. Enable BGP fast fall-Over in ROUTER-NEIGHBOR mode.
    fall-over

Configure neighbor fall-over

OS10(config)# router bgp 100
                                 OS10(config-router-bgp-100)# neighbor 3.1.1.1
                                 OS10(config-router-neighbor)# remote-as 100
                                 OS10(config-router-neighbor)# fall-over
                                 OS10(config-router-neighbor)# no shutdown
                              

Verify neighbor fall-over on neighbor

OS10(config-router-neighbor)# do show ip bgp neighbors 3.1.1.1
                                 BGP neighbor is 3.1.1.1, remote AS 100, local AS 100  internal link
                                 
                                 BGP version 4, remote router ID 3.3.3.33
                                 BGP state ESTABLISHED, in this state for 00:17:17
                                 Last read 00:27:54 seconds
                                 Hold time is 180, keepalive interval is 60 seconds
                                 Configured hold time is 180, keepalive interval is 60 seconds
                                 Fall-over enabled
                                 
                                 Received 23 messages
                                 1 opens, 0 notifications, 1 updates
                                 21 keepalives, 0 route refresh requests
                                 Sent 21 messages
                                 1 opens, 0 notifications, 0 updates
                                 20 keepalives, 0 route refresh requests
                                 Minimum time between advertisement runs is 30 seconds
                                 Minimum time before advertisements start is 0 seconds
                                 Capabilities received from neighbor for IPv4 Unicast:
                                 MULTIPROTO_EXT(1)
                                 ROUTE_REFRESH(2)
                                 CISCO_ROUTE_REFRESH(128)
                                 4_OCTET_AS(65)
                                 Capabilities advertised to neighbor for IPv4 Unicast:
                                 MULTIPROTO_EXT(1)
                                 ROUTE_REFRESH(2)
                                 CISCO_ROUTE_REFRESH(128)
                                 4_OCTET_AS(65)
                                 Prefixes accepted 3, Prefixes advertised 0
                                 Connections established 1; dropped 0
                                 Last reset never
                                 For address family: IPv4 Unicast
                                 Allow local AS number 0 times in AS-PATH attribute
                                 Prefixes ignored due to:
                                 Martian address  0, Our own AS in AS-PATH 0
                                 Invalid Nexthop  0, Invalid AS-PATH length 0
                                 Wellknown community 0, Locally originated 0
                                 
                                 For address family: IPv6 Unicast
                                 Allow local AS number 0 times in AS-PATH attribute
                                 Local host: 3.1.1.3, Local port: 58633
                                 Foreign host: 3.1.1.1, Foreign port: 179
                              

Verify neighbor fall-over on peer-group

OS10# show running-configuration
                                 
                                 !
                                 router bgp 102
                                 !
                                 address-family ipv4 unicast
                                 aggregate-address 6.1.0.0/16
                                 !
                                 neighbor 40.1.1.2
                                 inherit template bgppg
                                 no shutdown
                                 !
                                 neighbor 60.1.1.2
                                 inherit template bgppg
                                 no shutdown
                                 !
                                 neighbor 32.1.1.2
                                 remote-as 100
                                 no shutdown
                                 !
                                 template bgppg
                                 fall-over
                                 remote-as 102
                                 !
                              

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