CCM 8.5 limitation in H323 Session

Unanswered Question
Dec 10th, 2011
User Badges:


I implement a cucm cluster in a company, they also have a panasonic IP PBX that connects to the PSTN PRI line.

The problem is when the total active h323 connections to PBX reaches to 14-15 sessions, clients get fast busy signal,

I checked the PBX h323 license, it has a 32 concurrent h323 license,

I'd like to know whether the cisco ccm  has a limitation on H323 or not?

and if not what could be a possible problem?



  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
Dennis Mink Sat, 12/10/2011 - 04:38
User Badges:
  • Gold, 750 points or more


there is no such limitation, I have set up dozens of full PRI's using 30 channels (Onramp 30's as they are called here in Australia), so definitely there is NO out of the box limitation.

If I understand you set up corrently, you have phones, registered on CUCM which has a TRUNK to the Panasonic PBX which connect to PSTN. is this correct?

would have been nice with an IOS gateway in between, would have made it easer to trouble shoot,

is you are looking at troubleshooting H323 on CUCM, yeah well, that is an art on itself.

This link is got a pretty good description, maybe you could start there:

please rate if helpfull

Hythim Ali El Hadad Sat, 12/10/2011 - 11:45
User Badges:
  • Silver, 250 points or more

if you are using cisco 800 series as a CUBE, it is yes that it has a max of 15 CUBE sessions

Another models support more more numbers than this

If not.

Check if you have applied CAC to your trunk from CUCM side ?

If not

It is the other BPX issue, it may be licensed to use 32 but not configured well to use the 32 sessions

Some default fw configuration is set to 16 max sessions



mazloumi.arash Sat, 12/10/2011 - 21:03
User Badges:

Dear friends

Thanks for your reply

I also thinks the problem relies in the PBX, first they have 16 session license but after we faced this problem they upgrade their license to 32 and add another gateway virtual card to extend h323 session to 32 but maybe another configuration needed to apply.

The current topology is what that minkdennis refered that but we have two ccm, when i monitor h323 session in RTMT usually the subscriber have about 10 session and publisher have 4-5 session,

The CAC in not configured on cluster and we dont have CUBE,

I configured QSIG tunnel under cucm gateway configuration for solving some issues between PBX and CCMs, is it possible this config caused the problem?



This Discussion