Information Technology Reference
In-Depth Information
Table 7-39 lists some of the similarities and differences between route reflection and
confederation.
Table 7-39
Route Reflection and Confederation Comparison
Parameter
Comparison
Multilevel hierarchy
Both methods support hierarchies to further increase scalability.
Route reflection supports hierarchical route reflection. Confedera-
tion allows route reflection to be used within a member AS.
Policy control
Both provide routing policy control, although confederation might
offer more flexibility.
Regular iBGP migration
complexity
Migration complexity is very low for route reflection, because few
changes to overall network configuration occur. However, migration
from iBGP to confederation requires major changes to the configu-
ration and architecture. Chapter 8 provides two case studies on how
to migrate from an iBGP architecture to an RR- or confederation-
based architecture.
Capability support
All routers within the confederation must support confederation
capability, because all routers need to understand the confederation
AS_PATH attribute. In a route reflection architecture, only RRs are
required to support route reflection capability. With the new cluster-
ing design, however, clients must also understand RR attributes.
Because both route reflection and confederation were introduced in
IOS in very early releases, this feature comparison is not really
important. In fact, it is better to have all the routers support route
reflection even though you are not using the new clustering design,
because that gives you the flexibility to use the design in the future.
IGP expansion
Route reflection requires a single IGP inside an AS, whereas con-
federation supports single or separate IGPs. This is probably the
most distinctive advantage of confederation over route reflection. If
your IGP is reaching its scalability limit or it is just too big to han-
dle administration, confederation can be used to reduce the size of
the IGP tables.
Deployment experience
Because many more service providers have deployed route reflec-
tion than confederation, much more experience has been gained for
route reflection.
AS merge
AS merge is actually irrelevant to iBGP scalability, but it is included
here because it is one of the benefits of confederation. An AS can be
merged with an existing confederation by treating the new AS as a
sub-AS of the confederation. AS merge in an RR environment is
much more disruptive.
