Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. If you'd prefer to explore, try our test area to get started. And see here for current known issues.

New Member

Backplane speeds

How important is it to determine the amount of backplane throughput you will need for equipment? How do you determine how much is enough? ie I am trying to make a decision between the 2800 series routers. I need to support at least 2 T1's and up to 400 users. What size is suitible? Any help is appreciated, thank you.



Re: Backplane speeds

Sorry couldn't find the capacity charts that have been posted to these forums before.

If all you are going to do is run from the ethernet port to the 2 t1 lines a 2801 will easily do that even with QoS and NAT. The issue would come if you tried to do ethernet to ethernet.

I would go for the 2811 at least just because it allows for more future expansion than a 2801. If money is your primary issue I have many sites on 1841 running 2 t1 lines using nat,QoS and mulitlink frame relay with no issues.

But then again old 2501 used to run 2 t1 lines with no issues.

New Member

Re: Backplane speeds

Thanks Tim. What about the general question of backplane speeds not realating to the 2800's? We need to support at least 2 t1's with possible expansion. We were also looking at the 2821's because the price difference between the 11 and 21 is only a few hundred bucks. Also, we are trying to stay w/ the adv ip services.


Re: Backplane speeds

Here is the doc I think Tim was looking for:

You'll be able to see here that any 2800 series will handle 2 T1's without breaking a sweat.

Also, keep in mind that it isn't the backplane that limits the performance of these routers (usually), but the CPU. Every time a packet needs to be switched it generates a CPU interrupt, and the CPU needs to make the switching decision (and if configured, do QoS, ACL, VPN, etc). Faster the CPU, the more interrupts it can handle, and the more packet switching power you have.