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Border Gateway Protocol IPv4 (BGPv4) | 267
BGP Regular Expression Optimization
BGP policies that contain regular expressions to match against as-paths and communities might take a lot
of CPU processing time, thus affect BGP routing convergence. Also,
show bgp commands that get filtered
through regular expressions can to take a lot of CPU cycles, especially when the database is large. FTOS
optimizes processing time when using regular expressions by caching and re-using regular expression
evaluated results, at the expense of some memory in RP1 processor. This feature is turned on by default.
Use the command
bgp regex-eval-optz-disable in CONFIGURATION ROUTER BGP mode to
disable it if necessary.
Retain NH in BGP Advertisement
BGP does not update the NEXT_HOP attribute if it is a Route-Reflector. bgp retain-ibgp-nexthop can be
configured to retain the NEXT_HOP attribute when advertising to internal BGP peer.
Debugging BGP
Use any of the commands in EXEC Privilege mode to enable BGP debugging.
Command Syntax Command Mode Purpose
debug ip bgp [ip-address | peer-group
peer-group-name] [in | out]
EXEC Privilege View all information on BGP, including BGP
events, keepalives, notifications, and updates.
debug ip bgp dampening [in | out] EXEC Privilege View information on BGP route being
dampened.
debug ip bgp [ip-address | peer-group
peer-group-name] events [in | out]
EXEC Privilege View information on local BGP state changes
and other BGP events.
debug ip bgp [ip-address | peer-group
peer-group-name] keepalive [in | out]
EXEC Privilege View information about BGP KEEPALIVE
messages.
debug ip bgp [ip-address | peer-group
peer-group-name] notifications [in | out]
EXEC Privilege View information about BGP notifications
received from or sent to neighbors.
debug ip bgp [ip-address | peer-group
peer-group-name] updates [in | out]
[prefix-list name]
EXEC Privilege View information about BGP updates and filter
by prefix name