Information Technology Reference
In-Depth Information
Figure 7-2
BGP Route Reflection Components
AS 100
R1
R2
eBGP
eBGP
R3
R4
AS 200
Client
R6
RR
Client
R5
R7
eBGP
R8
AS 300
Physical
iBGP
Rules for Prefix Advertisement
Before discussing the rules for prefix advertisement, a definition is in order. As a special
form of prefix advertisement, reflection is the advertisement made by an RR for prefixes
learned from one client to another client, from a client to a nonclient, or from a nonclient
to a client. In this definition, the following advertisements are not examples of reflection:
from an external peer to an RR, from an RR to an external peer, or from an RR to an internal
peer (client or nonclient) for a prefix learned from an external peer. In summary, reflection
is a concept that is introduced with RRs and is used as a subset of the advertisement
concept.
To avoid creating routing information loops, certain rules must be followed during prefix
advertisement involving RRs:
•
Rule 1
—An RR advertises or reflects only its best path.
•
Rule 2
—An RR always advertises to eBGP peers.
