Eigrp AS Number and Hop Count relation

[vikrant.pandey@gmail.com]

As per my thinking , but you please certified or modified , is that as the max hot count for this eigrp is 255 and if an enterprise (for example) have 1000 routers and need to have only eigrp in all , then can distribute 200 RTRs in eigrp AS 1 then another 200 RTRs in AS 2 and so on, so please put ur suggestion .

[balaji.bandi · Accepted solution]

It all depends how your network geographycally streached, if they can not be part of main AS for a reason, yes you can do that.. again this recomendation based on your input only.

In general, we make them in area wide PoP (Point of Presense) where most of the PoP participate in Main AS, and oher local devices connected to local PoP.

[Giuseppe Larosa · Accepted solution]

Hello Vikrant,

EIGRP uses the maximum hop count actually as a way to limit the scope of valid EIGRP advertisements.

The default value for maximum hop count is 100 and can be increased up to 255 as it actually maps to IPv4 header TTL field.

If you have 1000 routers in your internetwork this does not mean you need 5 different EIGRP AS domains.

Hop count is the number of routers the EIGRP advertisements has gone through.

This depends on topology, but unless your network is a daisy chain of routers the maximum hop count is usually much lower then the total number of routers.

The use of multiple EIGRP domains is a scalability decision in order to help minimize the range of Queries.

However, in the past EIGRP queries could propagate from one EIGRP domain to another one.

This behaviour was an error in implementation. This should have been fixed.

Edit:

Scalability design for EIGRP requires control on EIGRP queries range.

This can be achieved using EIGRP stub router function on routers that are leaf (there are no other routers downstream of them) and using EIGRP route summarization on core devices.

EIGRP is well suited for hub and spoke topologies like for example DMVPN and can support hundreds of spoke routers.

Hope to help

Giuseppe

[vikrant.pandey@gmail.com]

Thank you very much for ur reply . Here in ur reply u mentioned "multiple EIGRP domains" , so is this multiple means different Eigrp AS No.

[Giuseppe Larosa · Accepted solution]

Hello Vikrant,

thanks for your kind remarks

yes your understanding is correct multiple EIGRP domains = using different EIGRP AS numbers one for each domain.

Hope to help

Giuseppe