EIGRP Stub Design Query

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Sep 30th, 2009
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Dear Experts,


Need your quick help on EIGRP Stub functionality for routed access layer design:


1)We have 2*CAT4503 E's installed with SUP6L-E cards and connected together via 2*10GBE port channel configured as layer 2 at the moment. As SUPL-E only supports EIGRP Stub, would my plan towards routed access layer (CAT3560's) work or do I need to upgrade the SUP card?


2)Does EIGRP Stub needs to be configured on the Access layer stacks only or distribution switches as well? If it require configuration on Distribution switches then do I need to convert my l2 port channel to l3 port channel and turn on EIGRP Stub on it as well? Or Do I need to have full EIGRP on the distribution switches and EIGRP Stub in access layer?


3)We have all access layer stacks connected via dual uplinks to CAT4503's and running PVRSTP. Does configuring EIGRP Stub provide ECMP to load balance the traffic over two diverse paths?


Thanks

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Giuseppe Larosa Wed, 09/30/2009 - 06:50
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Hello JB,


>> Do I need to have full EIGRP on the distribution switches and EIGRP Stub in access layer?


yes indeed


EIGRP stub feature is for devices that haven't other routers downstream to them.


think of stub = leaf


So you need to place othe sups in your distribution devices they are good for a L2 access layer design not for a L3 routed access layer.


EIGRP stub can be used at access layer for help in limiting the EIGRP query range.


Hope to help

Giuseppe





csco11142276 Wed, 09/30/2009 - 07:26
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Thanks a lot Giuseppe for your response.


Any idea on if we can do ECMP on EIGRP Stub uplinks to enable load balancing?


Thanks in advance.

Giuseppe Larosa Wed, 09/30/2009 - 07:30
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Hello JB,


once you move to L3 links from access layer switches to distribution you can use L3 parallel load balancing if they appear as two equal cost paths they use it.


This is one of the advantages of a routed access layer


on a L2 access layer design is enough to make distrib1 root bridge for one half of vlans and distrib2 root bridge for the other half of vlans (per vlan STP mode) to achieve load sharing.


I will try to look at this ECMP ... :)


Hope to help

Giuseppe


csco11142276 Wed, 09/30/2009 - 07:37
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Giuseppe


Thanks again.


Each access layer switch will be connected to two 4503's over diversely routed 1Gbps uplinks running EIGRP stub i.e. one 1Gbps uplink terminating on the core switch 4503E_No1 and another 1Gbps uplink terminating on the core switch 4503E_No2. So, I take it from your mail that it will work the only upgrade I require is SUP cards.


Hmm, needs to check if management can handle this blow or just leave as it is as it may be too expensive to buy new SUP cards.





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