Redundancy setup - comments please..

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May 4th, 2009
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Would like opinions on the following setup - Limited budget, we are attempting to have relatively simple cut-over should we lose primary switch.

7200 w/ NPE-G2 (2 Gb ports in PortChannel)

3560 48 Gb ports (Primary Switch) - 2 Gb ports in PortChannel

2960 48 Gb ports (Backup Switch) - 2 Gb ports in PortChannel

All three devices managed via OOB w/ 2509

Theory is that new services are added as portchan dot1q Ints to 7200(And vlans on 3560+2960), and in the event we lost 3560, we could simply patch the 2960 into the 7200 and we would be operational again(Obviously we would also need to re-patch any active ports on 3560->2960)

We would also have redundant 7200(w/ NPE-400)

Thanks in advance for comments.

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Giuseppe Larosa Tue, 05/05/2009 - 05:20
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Hello John,

when you have also a redundant C7200 with NPE-400 you can have:

first C7200 with NPE-G2 active router on all client vlans using HSRP

c7200 with npe-400 connnected with an FE to C2960 would be secondary router on each HSRP group.

this will allow you to be redundant without need to swap cables, performance of secondary will be reduced.

Another possible design is to have the C3560 to work for intervlan-routing together with the other two.

Hope to help


johnelliot6 Tue, 05/05/2009 - 13:10
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Hi - Thanks for the response.

Reason for Portchan's was that we are currently exceeding 100Mb, therefore 2 x 10/100 ports from NPE-400 we can get 200Mb.

Clients have co-located devices connected to if we lost 3560, we would need to physically re-patch.

Joseph W. Doherty Wed, 05/06/2009 - 03:27
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BTW, a NPE-400 might be unable to deliver 200 Mbps (duplex) of performance.

johnelliot6 Wed, 05/06/2009 - 12:25
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Thanks Joseph - We have SmartNet on 7200 w/G2, so the NPE-400 would only be used until replacement hardware arrived for G2 etc.

So, based on our requirements - Is the portchan solution viable?

Joseph W. Doherty Wed, 05/06/2009 - 16:04
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Line rate for 100 Mbps Ethernet with minimum sized packets requires 148.8 Kpps. So dual port channel 100 Mbps, duplex, could require 595.2 Kpps. The NPE-400 is rated at about 400 Kpps, the NPE-G2 is rated at about 2 Mpps. Should be fine on a -G2; on a -400 you could run short.


Except for redundancy, gig would be better than a dual 100 Mbps port channel. (It's not just 10x the bandwidth, it's also port channels direct flows to only one link. This means single flow can obtain only single link's bandwidth and it's also possible two flows can use one link while other is unused.)

For only 200 Mbps of traffic, dual gig port channels could decrease average serialization delay, but for so light a load, it would offer minimal benefit.

johnelliot6 Wed, 05/06/2009 - 16:10
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Thanks Joseph - We were also thinking from the perspective of maintaining config consistency between the 7200's...with Portchan, it would simply be a matter of copying what is added to G2 7200 directly to the NPE-400 7200.

Obviously the 7200 w/ NPE-400 is not ideal, but as stated, we have strict budget.

Thanks again for your assistance.


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