Peer Group; Route Reflector - Huawei S6700 Series Configuration Manual

S6700 Series Ethernet Switches
Configuration Guide - IP Routing

Peer Group

A peer group is a group of peers with the same policies. After a peer is added to a peer group,
it inherits the configurations of this peer group. When the configurations of the peer group are
changed, the configurations of peers in the peer group are changed accordingly.
On a large-scale BGP network, there are a large number of peers and most of them have the
same policies. To configure these peers, you have to repeatedly use some commands. In such a
case, you can simplify configurations by using the peer group.
Adding many peers to a peer group also speeds up route advertisement.

Route Reflector

To ensure the routing synchronization between IBGP peers, you need to establish full-mesh
connections between the IBGP peers. If there are n switchs in an AS, n (n-1)/2 IBGP connections
need to be established. When there are a large number of IBGP peers, network resources and
CPU resources are greatly consumed.
To solve this problem, route reflection is introduced. In an AS, one switch functions as a route
reflector (RR) and other switchs serve as the clients of the RR. The clients establish IBGP
connections with the RR. The RR transmits or reflects routes among clients, and the clients do
not need to establish BGP connections.
A BGP switch that is neither an RR nor a client is a non-client. Full-mesh connections must be
established between non-clients and an RR, and between all non-clients.
Confederation
Confederation is another method of dealing with increasing IBGP connections in an AS. It
divides an AS into several sub-ASs. IBGP connections are established between IBGP peers
within each sub-AS, and EBGP connections are established between sub-ASs.
For BGP speakers outside a confederation, sub-ASs in the same confederation are invisible.
External devices do not need to know the topology of each sub-AS. The confederation ID is the
AS number that is used to identify the entire confederation.
The confederation has disadvantages. That is, if the switch needs to be reconfigured in a
confederation, the logical typology changes accordingly.
On a large-scale BGP network, the RR and confederation can be used together.
Community
The community attribute is a route attribute. It is transmitted between BGP peers and is not
restricted by the AS. A peer group allows a group of peers to share the same policies, whereas
the community allows a group of BGP routers in multiple ASs to share the same policies.
Before a BGP switch advertises the route with the community attribute to other peers, it can
change the community attribute of this route.
Besides well-known communities, you can use a community filter to filter self-defined extended
community attributes to control routing policies in a more flexible manner.
Issue 01 (2012-03-15) Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
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