National Ethernet Questions.

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Mar 9th, 2012
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Hey everyone,

Another question regarding my university project.

I am insisting using layer 2 connectivity between the HQ and 5 branch offices as point-to-multipoint but before I can implement this solution I need to understand the equipment that the ISP would install at the HQ and branch offices.

I need to create resilience between the offices so have to implement dual connections. I am using 2 distribution layer 2 switches for resilience and plan to connect each Ethernet connection to the offices but I am unsure of how in will be able to load balance. What protocol will I use? Also should I run STP over the ethernet connections? Or should I run a separate STP that isn't associated with the branch office to prevent bridging loops?

What equipment does the ISP install at each office? As I implementing dual connections for resiliency do they install double equipment? Does the ISP run any protocols I should I take not of that will cause issues?

I am not 100% sure how I should do this. Any advice would be appreciated.

King regards,


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Peter Paluch Fri, 03/09/2012 - 16:25
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Would you mind posting a quick sketch of how you expect your HQ/branch offices to be interconnected, including the dual connections etc.?

Best regards,


Kishore Chennupati Sat, 03/10/2012 - 02:47
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hi john,

if you thinking of your dual links to share the load etc then in my opinion the solution would be to use VSS on cisco 6500 switches and vPC if using nexus 7k at your HQ. so essentially the design would be that there will be 2 switches at the HQ and each one of them having a link to branch each site so it sort of becomes like a hub and spoke sort of network but at Layer2. This also eliminates STP not entirely but no more trouble of STP loops etc if you use technology like VSS and vPC. If you google around on those topics you can see several references which will give you a good idea.

check this link

If the above doesnt fit your case then please post the diagram as per peters advise



JohnNarey Sat, 03/10/2012 - 05:05
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Hey Peter and Kishore,

Here is an attached image of the layout in Packet Tracer.

The top left is the HQ along with the server farm containing the DHCP server for the branch offices, and the other 4 are the branch offices. I am using 2 hubs in the middle to connect the dual links because in my head I believe that National Ethernet point-to-multipoint frames are transmitted similar to a hub transmission. Maybe I am wrong in thinking this. Kishore the only Cisco equipment I can use are Catalyst 3560 for Distribution Layer Switches for VLANs and Catalyst 2690 for Access Layer Switches to match what we have in the lab. I can ask to change too different models if needed.




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