How can I improve my BGP convergence time?

Optimizing BGP and IGP interaction requires the following: Tuning the underlying IGP for fast convergence. It is possible to tune the IGP even for large network to converge under one second. Enabling BGP Next-Hop Tracking process for all BGP speakers and tuning the BGP NHT delay in accordance with IGP response time.

What are the default BGP timers?

The BGP Advertisement interval is a timer that decides how much time must elapse between an advertisement/withdrawal of routes to a BGP peer. The default is 30 seconds for eBGP peers and 5 seconds for iBGP peers. This can be changed with the on a per neighbor basis.

How do I show timers in BGP?

To verify currently configured advertisement timer, you can look on show ip bgp neighbors to see it. The same output for iBGP session would show you advertisement timer set to 0 second by default as inside one AS, the updates should be propagated immediately.

Do BGP hold timers need to match?

This message also carries hold time configured on the peer. The common myth is both BGP peer mush have matching hold time and keep alive timer for BGP neighbor relationship. It is not true! Another myth is BGP peer sends keep alive timer in open message, it is not true either!

How long does BGP take to failover?

The failover time for the default i-BGP peering session with the default value of the waiting interval is 5 seconds. The failure time on the primary link does not affect the secondary link and tertiary link.

What is BGP failover?

If all BGP-sessions are up, That kind of failover will be done automatically. If the connection to one of the BGP-neighbor will fail, the BGP-session to that neighbor will go down and your multilayer switch will not receive a defaultroute anymore via that BGP-neighbor anymore.

What are the values of keepalive and dead timers in BGP?

The default value for the hold time suggested in the BGP specification (RFC 4271) is 90 seconds, and keepalives should be sent at intervals of one third the hold time (30 seconds). However, Cisco uses defaults of 180 and 60 seconds.

What is BGP scan timer?

BGP uses a scanner that checks all routes in the BGP table every 60 seconds. The BGP scanner does best path calculation, checks the next hop addresses, and if the next hops are reachable. 60 seconds is a long time.

How do you form a BGP Neighborship?

To configure the BGP peer sessions:

  1. Configure the interfaces to Peers A, B, C, and D.
  2. Set the autonomous system (AS) number.
  3. Create the BGP group, and add the external neighbor addresses.
  4. Specify the autonomous system (AS) number of the external AS.
  5. Add Peer D, and set the AS number at the individual neighbor level.

What is BGP hold time expired?

Summary: In normal scenarios, when a Border Gateway Protocol (BGP) peer goes down, a router only waits for the hold timer to expire to declare the neighborship as down (90 seconds default). But in some cases, a router will retain this dead adjacency up for a longer time even if the BGP timers have expired.

Can BGP do load balancing?

BGP cannot load balance between routes by route metrics as an IGP protocol does, because BGP does not have a route computation algorithm. BGP uses the following load balancing criteria to determine load balanced routes: The routes have the same ORIGIN, LOCAL_PREF, and MED attributes.