When BGP needs to choose which route to reach a certain destination is best, it first looks at the local preference and AS path attributes, as discussed in previous articles. When the local preference and AS path length are the same for two or more routes towards a...
In earlier articles, we discussed the next hop and local preference attributes. Today we’ll be looking at the AS_PATH attribute as well as the AS4_PATH attribute. What is an AS PATH? The BGP AS path is a well-known mandatory attribute, which means that...
In the previous blog post, we looked at the BGP NEXT_HOP attribute. Today we’ll cover another attribute: the LOCAL_PREF or local preference. What is LOCAL_PREF? The LOCAL_PREF (local preference) is the first attribute a Cisco router looks at to determine which...
Once a BGP session is established, routers will exchange two types of messages: KEEPALIVE and UPDATE. Keepalive messages are sent to let a neighboring router know we are still alive, but just didn’t have any updates to send. The update message carries three...
