Redundant conection between 2x3750 and a c7200

Unanswered Question
Feb 11th, 2009


We would like to design a network redundant to a fail of a switch. We have 2x3750E and use the Cisco stackwise technology. We don't know the best way to connect a router c7200 to the two swiches. We consider two options:

1.In the c7200 define a BVI and a bridge-group between two Gigabit interfaces, one connected each switch. So STP (802.1d) are responsible of decide with link must be active. If a link or switch fails, after 30 seconds of convergence, the router will be accessible again. I have look if a C7200 support RSTP (802.1d) or UplinkFast but I think it doesn't support this features that would let better converge times.

2.Use an Etherchannel. Cisco stackwise lets an etherchannel form by one link to each 3750. The problem is that I am not sure if a EtherChannel in a c7200 is LACP compliance. I suppose that a c7200 it only support MAC destination load-balancing. For other reasons, I need to active source-destination IP address load-balancing in the 2xc3750. I am not sure if a load balance method in each end is recommended. Perhaps it produces some problem with the order of the packets or something similar.

Which one is the best design? Is there another solutions?.


I have this problem too.
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JamesLuther Thu, 02/12/2009 - 05:45


It is preferable to use an Etherchannel for several reasons. Firstly, you don't want to cause a spanning tree event if a link goes down and secondly you will get greater throughput (without having to balance vlans).

If you configure the etherchannel to be "channel-group 99 mode on" on the switch side then you don't need to worry about LACP.



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