Information Technology Reference
In-Depth Information
n 2 Issues for Full iBGP Mesh
Figure 7-1
5000
4500
4000
3500
3000
2500
2000
1500
1000
500
0
2 0 0 0 0 0 0 0 0 0 0
Number of iBGP-speaking Routers
Two effective approaches to solve the iBGP scalability issue are route reflection (RFC
2796) and confederation (RFC 3065). Route reflection is based on relaxing the iBGP loop-
prevention requirement for certain types of routers, whereas confederation is a method of
breaking a large AS into a number of smaller member autonomous systems. Either way, the
number of iBGP sessions can be reduced to a manageable level.
Route Reflection
This section discusses various aspects of route reflection:
How route reflection works
Rules for prefix advertisement
Clustering
Loop-prevention mechanisms
Hierarchical route reflection
Route reflection design examples
How Route Reflection Works
Route reflection involves creating a special group of routers called route reflectors (RRs).
The iBGP loop-prevention rule is relaxed for these routers, in that with certain restrictions
 
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