Dell EMC SmartFabric OS10 User Guide Release 10.5.0

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 you enable fail-over, 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
!