Minimum requirements for CME on 2911?

[voip7372]

We have a 2911 router that's currently configured to be a SIP trunk on CUCM along with media resources for transcoding, MTP and conference.  We have a request to remove this router from CUCM as a voice gateway and reconfigure it for use as a standalone Call Manager Express.  That router has an E1 R2 circuit already configured as well (just 1 circuit).  The router also has a 64 channel PVDM, 512 MB of DRAM, 256 MB of flash and the UC-K9 license.   The router has IOS version 15.2(4)M6a which I believe equates to CME version 9.1 and from what I can tell, the 6945 SIP phones and CIPC as SCCP would be supported on that version.  Correct me if I'm wrong.

I already checked the specs that Cisco recommends for CME and they say you 'should' have 1 GB or DRAM and 256 MB of flash if you use the 2911 for CME.  The big question is, can we use this for CME with only 512 MB of DRAM or will this truly cause problems?   We will have approximately 18 model 6945 (SIP) phones registered and maybe 2 or 3 CIPC (SCCP) softphones.  There are around 25 total phones I see existing in CUCM but only 18 are actually registered so I think that's what they're truly using.

Have any of you used a router in this scenario with only 512 MB of DRAM for CME and this amount of phones?  This router is in another country and it's not easy for us to arrange to have it updated with me DRAM.

[R0g22 · Accepted solution]

Yes the recommendation for CME 9.1 on a ISR 2911 is 1 GIG DRAM. You can run it with 512 MB as well but it all comes down to what all other configuration do you have.
Primary memory usage for you would be dial-peers. Each dial-peer assumes around 6k memory. You are not supposed to breach 80% of the total memory utilisation on the router.
Do the calculations, create a simplified dial-plan and you should be good. If you plan to have tons of shared lines/DN's and would be creating lots of dial-peers, 512 MB might not be enough. I have seen deployments where 1 GB is not enough as well. It all comes down to what your config looks like.

[voip7372]

Great, thank you.  Our dial-peers would be pretty simple.  I'll try to come up with a close example of what the config would look like and then use your calculations for how much each dial-peer would consume and see where we are before we agree to do this at that location.