notes: BGP Fast External Fallover & Maximum Prefix

Fast External Fallover
- Fast External Fallover for external peers are triggered by a session flap, based upon the receipt of
an interface change notification.
- By default, when a local BGP interfaces goes down, the BGP neighbors on that interface is shutdown as soon as a interface reset
is detected, appose to waiting for the holddown timer (default = 180sec) to expire.
- Disabling BGP fast external fallover, will wait for the holddown timer to expire, before shutting down the neighbor sessions


commands:

- [Disables] Enables Fast External Fallover globally, thus waits for hold-time to expire

router bgp {asn}

[no] bgp fast-external-fallover 

Interface Configurationg

int s0/0

ip bgp fast-external-fallover permit - Allows per-interface fast external fallover
ip bgp fast-external-fallover deny - Prevents per-interface fast external fallover
no ip bgp fast-external-fallover - ONLY removes previously configured interface config, doesnot disable fall-over


Maximum Prefix

neighbor {IP} maximum-prefix {max no} [threshold] [warning-only] [restart {interval}]

- Controls how many prefixes can be received from a neighbor
- [Threshold]: The percentage when message is logged (default is 75%)
- [Warning-only]: When exceeding the maximum number apose to dropping the session
- [Restart] : Re-establish the session after the specified interval in minutes