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Configuring BGP
Configuring Basic BGP Features
IPC-309
Cisco IOS IP Configuration Guide
Disabling Next Hop Processing Using a Specific Address
To disable next hop processing and provide a specific address to be used instead of the next hop address,
use the following command in router configuration mode:
Configuring this command causes the current router to advertise its peering address as the next hop for
the specified neighbor. Therefore, other BGP neighbors will forward to it packets for that address. This
configuration is useful in a nonmeshed environment because you know that a path exists from the present
router to that address. In a fully meshed environment, this configuration is not useful because it will
result in unnecessary extra hops and because there might be a direct access through the fully meshed
cloud with fewer hops.
Disabling Next Hop Processing Using a Route Map
To override the inbound next hop setting for BGP routes and specify that the next hop of the matching
routes is to be the IP address of the remote peer, or to set the peering address of the local router to be the
next hop of the matching routes, use the neighbor next-hop-self router configuration command.
To configure the neighbor peering address to be used for the next hop address, use the following
command in route map configuration mode:
Configuring BGP Next Hop Propagation
The BGP Next Hop Propagation feature provides additional flexibility when designing and migrating
networks. The BGP Next Hop Propagation feature allows a route reflector to modify the next hop
attribute for a reflected route and allows BGP to send an update to an eBGP multihop peer with the next
hop attribute unchanged.
Caution Incorrectly setting BGP attributes for a route reflector can cause inconsistent routing, routing loops,
or a loss of connectivity. Setting BGP attributes for a route reflector should be attempted only by an
experienced network operator.
Command Purpose
Router(config-router)# neighbor {ip-address |
peer-group-name} next-hop-self
Disables next hop processing on BGP updates to a neighbor.
Command Purpose
Router(config-route-map)# set ip next-hop ip-address
[...ip-address] [peer-address]
In an inbound route map of a BGP peer, sets the next hop of
the matching routes to be the neighbor peering address,
overriding any third-party next hops and allowing the same
route map to be applied to multiple BGP peers to override
third-party next hops.
With an outbound route map of a BGP peer, sets the next hop
of the received address to the peering address of the local
router, disabling the next hop calculation.
The next hop must be an adjacent router.