User's Manual

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Users Manual of CS-6306R
45.4.2.1.5 Configuring Synchronization Between BGP and IGPs
If an AS sends information at the third AS through your AS, the internal routing state of your AS must be the
same as the routing information that the AS broadcasts to other ASs. For example, before all routers in your
AS learn the routes through IGP, your AS may receive routing information from your BGP that some routers
cannot route. The synchronization between BGP and IGP is that the BGP does not broadcast the routing
information until all IGP routers in the AS learn the routing information. The synchronization is activated by
default.
In some cases, you need not to perform the synchronization between BGP and IGP. If other ASs are not
allowed to send data through your AS, or if all routers in your AS run BGP, the synchronization will be
cancelled. After the synchronization is cancelled, your IGP can carry a few routes and BGP will aggregate
more rapidly.
Run the following command to cancel the synchronization
:
Command Purpose
no synchronization
Cancel the synchronization between
BGP and IGP.
When cancelling the synchronization, you need to run the command clear ip bgp to clear BGP sessions.
For details, refer to the section “Example for Neighbor-Based BGP Path Filtration”.
In general, only one or two routes are forwarded to your IGP and become the exterior routes in IGRP or the
BGP session sponsor generates a default AS route. When the routes are forwarded from BGP to IGP, only the
routes obtained through EBGP can be forwarded. In most cases, your IGP is not redistributed to BGP; the
networks in the AS are listed by running the router configuration command network; your network, therefore,
will be broadcast. The network listed in this way is called as the local network; BGP has the origin attribute of
IGP. These routes, such as directly-connected routes, static routes or routes learned from IGP, must be in the
main IP routing table and be valid. In BGP routing process, the main IP routing table is scanned periodically to
detect whether local network exists and the BGP routing table is updated afterwards. Be careful when the
BGP forwards the routes. Routes in IGP may be forwarded by other routers through BGP. BGP potentially
sends information to IGP and IGP then sends the information back to BGP.
45.4.2.1.6 Configuring BGP Route Weight
BGP route weight is a number that is endowed to BGP route for controlling route choice process. The weight
is local for the router. The weight ranges from 0 to 65535. The default weight of the local BGP routes is 32768.
The route weight obtained from the neighbor is 0. The administrator can carry out the routing policy by
modifying the route weight.
Run the following command to configure the route weight:
Command Purpose
neighbor {ip-address } weight weight Designates a weight for all
neighbor’s routes.
You can also modify the route weight through the route map.