Filter
Top Products
Configuring the Routers
Issue 6 January 2008 367
Route Reflection
The CNA system must be a route reflector client to all of the edge routers that will operate within
the CNA system’s sphere of influence. When multiple edge routers are being configured for
route reflection, a BGP cluster ID is required. The number can be either a 32 bit integer or an IP
address; the same number must be used on each device on which routing tables are to be
placed under the direction of the CNA system.
bgp cluster-id 88
Now the parameters of the IBGP peering configuration from the edge router to the CNA system
need to be defined:
neighbor 172.16.6.4 remote-as 65002
neighbor 172.16.6.4 description IBGP to CNA
neighbor 172.16.6.4 route-reflector-client
neighbor 172.16.6.4 soft-reconfiguration inbound
neighbor 172.16.6.4 weight 200
The IP address used are the same configured on the CNA system. The remote-as command
identifies the peering as IBGP (because the remote AS number matches the AS number in the
bgp command). The description command adds some descriptive text to the configuration. The
route-reflector-client command designates the CNA system as a BGP route reflector client. The
soft-reconfiguration command allows the CNA system to make changes to the BGP
configuration without a session reset.
The weight command assigns a high value to the CNA system, which causes the edge router to
prefer the CNA system’s routing assertions over the natural BGP route selection. This
assignment is non-transitive, which means that the weighting is not communicated to other
IBGP or EBGP peers. The weight attribute is local to this router only. In the example, weight is
set to 200. The actual setting will be dependent on the local policies; the weight value should be
high enough to prevail over those policies.
Note:
Note: The CNA system has a built-in precaution that prevents its route assertions from
leaking beyond your edge router’s borders. The no-export attribute is always set
in all CNA BGP routing updates. This is not user configurable. This attribute
prohibits the router from passing routes that it has learned from the CNA system
to routers outside the local AS.