Upgrade router question due to company growth

Unanswered Question
May 20th, 2007

We have a 2811 router, which provides service to a ccm cluster (1 publisher and 1 subscriber), we have about 70 users using around 70 did's and the router also provides did's to be use for our Xmedius fax server about 70 did's.

Question is

our company is projecting about 100 more users (employees) meaning 100 more did's..and we also going to upgrade our xmedius fax server to next level..Is the 2811 capable of handling all this users? as well handling all these did's?

if we need another router (next level) which one do we need?..for a company of about lets say 300 employees (ip phones) and how many did's can a router handle? what depends on?

is there a cap? is there a limit? what is the best voice router out there?..will the 2811 do the job?

Thank you for your time

I have this problem too.
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lfulgenzi Sun, 05/20/2007 - 19:10

I'm not up to date on the 2811 and what sort of performance hit it can take, but the two things I can see here are whether or not you will be increasing the concurrent voice/fax load or just configuring it for the larger range of endpoints. Even if you double the number of endpoints, you may not be doubling the concurrent calls, which I think is what the routers are rated for. And of course, ports, etc. If your fine with the current h/w config, i.e. incoming lines, then you should be fine.

Also, if you are considering SRST, then you will definately have to upgrade your router. The 2811 is only rated for 36 phones (144 lines).



from the Q&A there doesn't seem to be any 'limit' to the number of voice calls as this is limited by the number of PVDMs. The 2811 can support a max of 2 PVDM2's.


Q. Are there limits to how many voice channels supported on any of the Cisco 2800 series integrated services routers?

A. The only platform with a limitation less than the physical capacity of the DSP slots is the Cisco 2801. This platform can support a maximum of 30 channels of digital voice (voice channels terminated on a DS-1 interface) regardless of codec selected. The Cisco 2801 can also support up to 12 channels of analog voice (voice channels terminated on FXO, FXS or BRI interfaces) coincident with the digital voice channels. Other installed DSP resources may be allocated for conferencing and transcoding, echo cancellation or Secure RTP.

You can also use the dsp calculator to help you with the limits for each router.


edit #2

I just tried configuring a 2811 with four T1s and 92 voice calls (4x23) and it came back with the following error:

Your configuration may exceed the CPU capacity of the Cisco 2811 router platform. Please consider a higher capacity platform.

So I guess the DSP calculator is a good tool to help in capacity planning.

I can seem to find any reference to the CPU capacities though.

edit #3

OK! I think I found it. The router poster shows # of digital voice calls. This should be a good guideline for you on which to select. This with the DSP calculator.


don't forget to rate responses - thanks

charlotterob Mon, 05/21/2007 - 05:03

Thank you very much for your comments and clarification and at this point i will go ahead and recommend a cisco 3845 router.

rob.huffman Mon, 05/21/2007 - 08:16

Hi Charlotte,

Just to add a note to Lelio's really great info (5 points for that answer Lelio :)

Another nice way to handle a change like this (if you have multiple PRI's/E1's) would be to use a second 2811 in a redundant mode. It does eliminate a "single point of failure" type setup.

Hope this helps!


charlotterob Mon, 05/21/2007 - 10:08

How can i configure a second 2811 as a redundant mode?..thank you for your help

rob.huffman Mon, 05/21/2007 - 10:35

Hi Charlotte,

What we did was to install 2x2811's and then split our PRI's over these Gateways. DID calls can route over any of these PRI's via Route Group/Route Lists that contain all Gateways. If one of the 2811's or VIC modules fails (B-Channels will Busy-Out) and calls are still routed over the remaining 2811 Gateway.

Hope this makes sense!


sohaildxbfze Mon, 05/21/2007 - 11:02


Its just the matter of..

- Configure 2nd router with same configuration on 1st router.

- Create 2 route groups in CCM, each one with viz versa gateway priority,,

e.g RG1 [Gw1 listed first then GW2]

RG2 [GW2 listed first then GW1]

- Assign RGs to Route List [RL]

- Assign RL to route pattern(s)

In H323 can use preference on each dialpeer

if it helps please rate the post


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