As Confederations; Route Reflector - Cisco Nexus 7000 Series Configuration Manual

Chapter 11 Configuring Advanced BGP
S e n d d o c u m e n t c o m m e n t s t o n e x u s 7 k - d o c f e e d b a c k @ c i s c o . c o m .
Figure 11-2
confederation.
Figure 11-2
AS20
Z
In this example, AS10 is split into two subautonomous systems, AS1 and AS2. Each subautonomous
system is fully meshed, but there is only one link between the subautonomous systems. By using AS
confederations, you can reduce the number of links compared to the fully meshed autonomous system
in Figure

Route Reflector

You can alternately reduce the iBGP mesh by using a route reflector configuration. route reflectors pass
learned routes to neighbors so that all iBGP peers do not need to be fully meshed.
Figure 11-1
D). Without route reflectors, when router A receives a route from an external neighbor, it advertises the
route to all three iBGP neighbors.
When you configure an iBGP peer to be a route reflector, it becomes responsible for passing iBGP
learned routes to a set of iBGP neighbors.
In Figure
router A, it advertises (reflects) the routes to routers C and D. Router A no longer has to advertise to both
routers C and D.
OL-20002-02
shows the BGP network from
AS Confederation
AS10
A
AS1
eBGP
iBGP
B
11-1.
shows a simple iBGP configuration with four meshed iBGP speakers (router A, B, C, and
11-3, router B is the route reflector. When the route reflector receives routes advertised from
Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 4.x
Figure 11-1, split into two subautonomous systems and one
C
AS2
Confederation
peers
iBGP
D
Information About Advanced BGP
11-5