BGP UPDATE and ROUTE REFRESH packets

[riad1990new]

Hello,

I'm trying to understand how often BGP UPDATE messages get exchanged between neighbors, I understand that when a BGP neighborship is first established, UPDATE messages get exchanged between neighbors, but let's say I've applied a routing-policy change, for example:

* I've added a new network command for prefix A.

* I've configured a filter for prefix B.

Would an UPDATE message get sent out to BGP neighbors in both cases? or just the case of the advertised prefix with the network command?

If UPDATE messages are sent when changes are configured and networks become unavailable, then why do we need features such as SOFT-RECONFIGURATION, or ROUTE-REFRESH BGP packets?

Thanks,
Riad.

[MHM Cisco World · Accepted solution]

* I've added a new network command for prefix A. <<- your router send BGP update 

* I've configured a filter for prefix B. <<- if you add filter (Inbound or Outbound) the router will not request update from neighbor

BUT I add filter and want to check it effect
you need 
hard-reset <<- here your router end tcp session (BGP) and start new tcp session (BGP), and this will already exchange new update and your new filter will effect prefix 
soft-reset <<- here your router save updates from previous BGP update and the router only apply new  filter to prefix. 

soft-reset need more memory than hard-rest

the last option is 
route-refresh <<- here your router ask update without end tcp session (BGP).

[riad1990new]

Thank you.

[MHM Cisco World]

You are so so welcome