CME and Gatekeeper

[Chris Deren]

What is required in order to be able to call CME phones via a GK? I have CCM trunk, NetMeeting, and CME h.323 GW registered with GK with zone prefix zone2 4* where CME DNs are in the 4XXX range, I can call CCM phone from CCME phones via GK, but I cannot do that the other way around? What am I missing?

Chris

[michael_davis]

Hey Chris,

A few things to look at:

1) Do you know for certain which incoming dial-peer is handling the call on CME? Incoming called is useful here to make it deterministic.

2) If so, is the tech prefix configured and being stripped? Does the codec match and not break CAC on the GK?

3) Is CME the only endpoint in zone2? If not, do you have a gw-priority 10 configured for zone prefix 4*? The default priority is 5, so the gatekeeper will tend to round-robin to multiple endpoints in a zone. Just a note that I've learned the hard way - priority 10 means "always" and priority 0 means "never"

4) Who's handling the tech-prefix? I mean, are you using a default-technology, or is it configured the same (or differently) in both CCM and CME? If you have a significant digits restriction on the CCM trunk, it may be stripping the tech prefix for you so you're not seeing it inbound on the CCM.

5) Is there a proxy or IP2IP gateway function involved? If so, watch closely your bandwidth allocations on the GK.

debug voip dialpeer all on CME

and

debug gatekeeper main 10

are your dial-plan and CAC friends. Failing that, I'd be looking at debug h225 asn1 & debug h245 asn1 really closely for things like codec, capset, and IP address mismatches.

Just some thoughts. If none of these hit home, post your GK and CME configs with those debugs so we're all on the same page.

HTH,

Michael

[Chris Deren]

Thanks Michael, as usually very helpful, debug gatek main 10 is awsome I did not know about this hidden command.

I am able to dial CME phones now but only if I configure the e164 numbers as static aliases, is there a way to get it working without it?

To answer your questions:

1) Yes

2)How do you strip a tech prefix on CME, do I need to use translation rule on the voip dial-peer?

3)Yes, only one endpoint

4) CME has tech-prefix of 2#, CM has 1# which is default

5) no proxy

I added a route patternof 2#XXXX on CCM and pointed to GK trunk, I can see it hitting GK and redirecting to CME, I am little confused as to why the prefix is forwarded to CME, I thought GK should strip it? If not how do I strip it on the incoming dial-peer?

I would prefer not having to dial tech-prefix, is it possible without the static aliases?

Chris

[thisisshanky]

You can use a num-exp in CME to convert the techprefixed number to the actual number.

num-exp 4#4001 4001.

GK passes the tech prefix along with the DNIS.

[michael_davis]

So what was happening was something like:

1) from CCM you were dial XXXX.

2) you matched route-pattern XXXX and sent the call out the trunk.

3) GK received an ARQ for XXXX, didn't see a tech prefix, and applied 1# (default) to create 1#XXXX.

4) CME was registered with a 2# prefix. 1#XXXX doesn't equal 2#XXXX so no match. ARJ returned to CCM.

You added route-pattern 2#XXXX.

1) from CCM you were dial XXXX.

2) you matched route-pattern XXXX and sent the call out the trunk as 2#XXXX.

3) GK received an ARQ for 2#XXXX.

4) CME was registered with a 2# prefix. 2#XXXX equals 2#XXXX so we have a match. ACF with CME IP address is returned to CCM.

5) CCM initiates a h225 setup to CME with 2#XXXX.

6) CME "knows" XXXX, but not 2#XXXX and disconnects with an unallocated number.

Play around with these tech-prefix handling strategies. All are valid depending on requirements.

1) Place the CCM tech prefix on that inbound voip dial-peer.

2) Or, make the CCM and CME tech prefixes the same. Do not use the default-technology command in the GK. Instead, manually configure it on the CCM trunk / CME - h323-gateway voip tech.

3) Do not configure tech prefixes on the CCM and CME. Use only the default tech prefix.

4) voice translation profile to strip the 1# from the inbound DN. It would be placed on the inbound dial-peer.

5) Aliases. You've already done this.

A few points to keep in mind.

The GK needs a tech prefix to route a call. It can be provided by the endpoint(s), or implied by the default-technology command.

It will route on the TP+DN combination, or just the TP.

If it is routing only on TP, then any endpoint registered with a matching TP and in the same zone as the inbound endpoint is eligible for the call. The GK will round robin them.

The gatekeeper only "strips" the tech-prefix for its own routing decision. It does not change the DN, which in this case includes the prefix.

Alias just say: "If I get a request for XXXX, return IP y.y.y.y." Normal call routing rules don't apply.

GKs are kind've like DNS. With DNS, the server receives a "name" request, and returns an IP.

GKs receive a DN, and return an IP. They do not actually set up connections for h323 endpoints. They provide authorization and IPs for the h225 portion of call set up. That's why there's no digit modification.

Michael

[thisisshanky]

As usual, great post Michael..I am gonna bookmark this thread!

[thisisshanky]

Chris,

Did you get this problem fixed ?

If you have the CME router registered to the gatekeeper, all the ephone-dns should also register as E.164 IDs under the gateway. If they register as E.164 IDs, you dont need to prefix the tech-prefix in the route pattern that sends calls from Callmanager to the CME via the gatekeeper

(Like recommended in Michael's post)

PSTNSw#sh gatek end

GATEKEEPER ENDPOINT REGISTRATION

================================

CallSignalAddr Port RASSignalAddr Port Zone Name Type Flags

--------------- ----- --------------- ----- --------- ---- -----

10.1.21.33 4639 10.1.21.33 4429 CCM VOIP-GW

H323-ID: TrunktoGK_1

Voice Capacity Max.= Avail.= Current.= 0

192.168.121.240 1720 192.168.121.240 49887 CME VOIP-GW

E164-ID: 6464214003

E164-ID: 6464214001

E164-ID: 6464214002

H323-ID: CMESite2

Voice Capacity Max.= Avail.= Current.= 0

Total number of active registrations = 2

Configuration of gatekeeper

gatekeeper

zone local CME cisco.com 10.1.11.4

zone local CCM cisco.com

zone prefix CCM 3*

gw-type-prefix 5#* default-technology

no shutdown

!

5# is the tech prefix for Callmanager

6# is the tech prefix for CME router

Configuration of CME router

interface FastEthernet0/0.2

description Voice VLAN

encapsulation dot1Q 121

ip address 192.168.121.240 255.255.255.0

ip helper-address 10.1.21.33

no snmp trap link-status

h323-gateway voip interface

h323-gateway voip id CME ipaddr 10.1.11.4 1719

h323-gateway voip h323-id CMESite2

h323-gateway voip tech-prefix 6#

ephone-dn 1 dual-line

number 4001 secondary 6464214001 no-reg primary

corlist incoming Site2Ph1

!

!

ephone-dn 2 dual-line

number 4002 secondary 6464214002 no-reg primary

corlist incoming Site2Ph2

!

!

ephone-dn 3 dual-line

number 4003 secondary 6464214003 no-reg primary

call-forward busy 3700

call-forward noan 3700 timeout 15

I used no-reg primary keyword so that only the secondary number registers with the Gatekeeper

One thing I noticed with this configuration is that if you dont specify a dialplan-pattern command under telephony-service, then the CME doesnt register the secondary numbers configured under ephone-dn. Something to watch out for.

Hope that makes sense!

[Chris Deren]

Shanky and Michael,

Your responses were really helpful, I got it to work, but I need to practice more with GKs and CME. I tried to rate your posts a while back and even today and it does not work. Not sure what the issue is.

Chris