Tag: BGP neighbor adjacency

BGP Neighbor Adjacency States: From IDLE to ESTABLISHED

BGP requires manual configuration of neighbors. Once neighbors are manually configured, it goes through 6 states until it is fully established. Knowing these states would help us determine the stage our connection is currently in. It is also very important in troubleshooting as it helps us understand what went wrong during adjacency.

BGP Neighbor Adjacency States

BGP Neighbor Adjacency States:

1. IDLE – This is normally can be seen if BGP is down / administratively down or just waiting for the next attempt. At this stage, no BGP incoming sessions are permitted.

My BGP is established between Culloden and Stirling sites and Culloden and Fyvie sites. But when I shut down s2/2 link between Culloden and Fyvie, my BGP went to IDLE state.

Culloden(config)#int s2/2
BGP-Neighbor-Adjacency-States: IDLE STATE


The Internet Protocol: Border Gateway Protocol (BGP) Overview

Border Gateway Protocol (BGP) is an exterior gateway protocol used on the internet and ISPs to exchange routing and reachability information. BGP is a layer 4 path vector routing protocol that uses port 179. It is the only EGP that is still in use today. The current BGP version is BGPv4 which was published as RFC 4271 in 2006.

Unlike other IGPs (OSPF, EIGRP, or RIP), BGP has many metrics or attributes in choosing the best path in the network. These attributes are for path manipulation. We will check it one by one as those attributes influence either inbound or outbound traffic.