Layer 3 Technologies - BGP

5 important questions on Layer 3 Technologies - BGP

What is the command to configure passive/active?

(config-router)#neighbor X.X.X.X transport connection-mode passive

Back to default (active) 

(config-router)#neighbor X.X.X.X transport connection-mode active

What is the command to configure BGP dynamic neighbors?

(config-router)# bgp listen [limit max-number | range network / length peer-group peer group- name]

What does the command neighbor x.x.x.x local-AS local-AS-number?


Local AS allows a router appear to be in a different AS from its real AS for eBGP peers.

It cannot be used with iBGP peers including confederations. It is useful for
merging ISPs during transition.
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What does the command neighbor x.x.x.x allowas-in?


Normally a BGP router will drop any updates from an eBGP peer which has its own AS in the path to prevent loops.


The allowas-in feature can be used to override this and would be used if you have a discontiguous AS.

What does the command (config-router)# bgp additional paths install?

This allows a backup route to be calculated and installed in the RIB

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