Concept Guide
Match a Clause with a Continue Clause
The continue feature can exist without a match clause.
Without a match clause, the continue clause executes and jumps to the specied route-map entry. With a match clause and a continue
clause, the match clause executes rst and the continue clause next in a specied route map entry. The continue clause launches only after
a successful match. The behavior is:
• A successful match with a continue clause—the route map executes the set clauses and then goes to the specied route map entry
after execution of the continue clause.
• If the next route map entry contains a continue clause, the route map executes the continue clause if a successful match occurs.
• If the next route map entry does not contain a continue clause, the route map evaluates normally. If a match does not occur, the route
map does not continue and falls-through to the next sequence number, if one exists
Set a Clause with a Continue Clause
If the route-map entry contains sets with the continue clause, the set actions operation is performed rst followed by the continue clause
jump to the specied route map entry.
• If a set actions operation occurs in the rst route map entry and then the same set action occurs with a dierent value in a subsequent
route map entry, the last set of actions overrides the previous set of actions with the same
set command.
• If the set community additive and set as-path prepend commands are congured, the communities and AS numbers are
prepended.
Conguring BGP Confederations
Another way to organize routers within an AS and reduce the mesh for IBGP peers is to congure BGP confederations.
As with route reectors, BGP confederations are recommended only for IBGP peering involving many IBGP peering sessions per router.
Basically, when you congure BGP confederations, you break the AS into smaller sub-AS, and to those outside your network, the
confederations appear as one AS. Within the confederation sub-AS, the IBGP neighbors are fully meshed and the MED, NEXT_HOP, and
LOCAL_PREF attributes are maintained between confederations.
To congure BGP confederations, use the following commands.
• Species the confederation ID.
CONFIG-ROUTER-BGP mode
bgp confederation identifier as-number
– as-number: from 0 to 65535 (2 Byte) or from 1 to 4294967295 (4 Byte).
• Species which confederation sub-AS are peers.
CONFIG-ROUTER-BGP mode
bgp confederation peers as-number [... as-number]
– as-number: from 0 to 65535 (2 Byte) or from 1 to 4294967295 (4 Byte).
All Confederation routers must be either 4 Byte or 2 Byte. You cannot have a mix of router ASN support.
To view the conguration, use the show config command in CONFIGURATION ROUTER BGP mode.
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Border Gateway Protocol (BGP)