Brocade Communications Systems Layer 3 Routing Configuration ICX 6650 - Manual (Page 336)

318 Brocade ICX 6650 Layer 3 Routing Configuration Guide
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Optional BGP4 configuration tasks
AS1 contains a cluster with two route reflectors and two clients. The route reflectors are fully
meshed with other BGP4 routers, but the clients are not fully meshed. They rely on the route
reflectors to propagate BGP4 route updates.
FIGURE 26 Example of a route reflector configuration
Route reflection based on RFC 2796
Route reflection on Brocade devices is based on RFC 2796. This updated RFC helps eliminate
routing loops that are possible in some implementations of the older specification, RFC 1966.
NOTE
The configuration procedure for route reflection is the same regardless of whether your software
release is using RFC 1966 or RFC 2796. However, the operation of the feature is different as
explained below.
RFC 2796 provides more details than RFC 1966 regarding the use of the route reflection attributes,
ORIGINATOR_ID and CLUSTER_LIST, to help prevent loops:
• ORIGINATOR_ID – Specifies the router ID of the BGP4 switch that originated the route. The
route reflector inserts this attribute when reflecting a route to an IBGP neighbor. If a BGP4
switch receives an advertisement that contains its own router ID as the ORIGINATOR_ID, the
switch discards the advertisement and does not forward it.
• CLUSTER_LIST – A list of the route reflection clusters through which the advertisement has
passed. A cluster contains a route reflector and its clients. When a route reflector reflects a
route, the route reflector adds its cluster ID to the front of the CLUSTER_LIST. If a route reflector
receives a route that has its own cluster ID, the switch discards the advertisement and does
not forward it.
The Brocade device handles the attributes as follows:
Route
Reflector 1
Route
Reflector 2
Route
Reflector
Client 1
Route
Reflector
Client 2
EBGP
IBGP
IBGP
IBGP
AS 1 AS 2
Cluster 1
10.0.1.0 10.0.2.0
Switch Switch
Switch