ECS4660-28F_Management Guide-R03

C HAPTER 51 | IP Routing Commands
Policy-based Routing for BGP
– 1913 –
◆ The route target (RT) attribute is used to identify sites that may receive
routes tagged with a specific route target. Using this attribute allows
that route to be placed in per-site forwarding tables used for routing
traffic received from the corresponding sites.
◆ The site of origin (SOO) attribute is used to identify the site from which
the provider edge (PE) router learned the route. All routes learned from
a particular site are assigned the same site of origin attribute, no
matter if a site is connected to a single PE router or multiple PE routers.
Filtering based on this extended community attribute can prevent
routing loops from occurring when a site is multi-homed.
EXAMPLE
Console(config)#route-map RD permit 13
Console(config-route-map)#match peer 192.168.0.99
Console(config-route-map)#set extcommunity 100:0 192.168.1.1:1
Console(config-route-map)#
set ip next-hop This command sets the next-hop for a routing message. Use the no form
to remove this entry from a route map.
SYNTAX
set ip next-hop {ip-address | peer-address}
no set ip next-hop [ip-address]
ip-address – An IPv4 address of the next hop, expressed in dotted
decimal notation.
peer-address – Sets the next hop as the BGP peering address.
COMMAND MODE
Route Map
COMMAND USAGE
◆ The IP address specified as the next hop need not be an adjacent
router.
◆ When this command is used with the peer-address keyword in an
inbound route map received from a BGP peer, the next hop of the
received matching routes are set to be the neighbor peer address,
overriding any other next hops.
◆ When this command is used with the peer-address keyword in an
outbound route map for a BGP peer, the next hop of the advertised
matching routes will be set to be the peering address of the local router,
thus disabling next hop calculation. This command therefore has finer
granularity than the neighbor next-hop-self command, because it can
set the next hop for some routes, but not others. While the neighbor
next-hop-self command sets the next hop for all routes sent to the
specified neighbor(s).