Layer 3 switch versus Router design ? 7206 and 3560

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Jul 16th, 2007
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Our WAN contains a number of regional hub sites each serving a number of remote sites. Reach regional hub is connected to our HQ via a variety of circuits. (Hub and spoke)

We are looking at upgrading a number of our regional hub WAN circuits as it turns out to be cheaper to go for a new (higher speed) offering from our telco. However, due to distance limitations we cannot terminate all of these new circuits at our HQ. We are planning to feed out-of-reach regional hubs back to HQ via other regional hubs that are within reach of our HQ via the new circuits. The worst case we have is as follows where 4 regional hubs are fed back to HQ via 100meg and 1Gig links. 1gig circuits will be presented as SC fibre and 100meg as RJ45.



SITE4==100mbps==SITE3==100mbps==SITE2==1gbps==SITE1==1gbps==HQ


The circuits should have plenty of capacity to handle the traffic load required but I need to determine which devices to use at each site.


The plan is as follows:


The old circuits terminate at our HQ on a pair of 7206VXR NPE400 so we plan to terminate the 1gig circuit at HQ on the above 7206 using PA-GE adapters. (We will actually have four of these circuits from various areas so will install two PA-GE in each 7206 which with our configuration is the maximum I believe in terms of ?bandwidth points?on each PCI bus).


Implement at 3560 with IP services image at site 1 to terminate the circuit from HQ and provide link to site2 (using GLC-SX-MM SFPs).


Site 2 has a 3745 installed so plan to install an NM-1GE module to provide gig link to site 1 and use on-board fast-eth to connect to site 3 at 100meg.


Site 3 and 4 also have 3745 and will connect via fast-eth interfaces.


The aggregate traffic from sites 2,3 and 4 traversing site1 back to HQ is not expected to exceed 100meg in the near future


There will be a backup link between site 4 and HQ to provide a certain level of resilience and we will probably configure routing to send traffic down this link by default.



An alternative would be to use 3825 at ?site1? with 2 off HWIC-1GE-SFP and implement a 3750G-12S with IP Services image for routing at HQ




So my question is after all that is ? are these reasonable designs in terms of device selection and throughput on circuits and devices?

Another question ? compared a router will a L3 switch offer better performance with regard to throughput ? I?m guessing yes but could anyone confirm?


Thanks in advance for any answers.


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bjornarsb Mon, 07/16/2007 - 10:23
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Hi,


The major difference not taking different interface into conciduration is that 3560 does not support netflow.


BR,


Bjornarsb



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