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New Member

question about remote ip phone can't dial out to PSTN

Problem description:

Local Cisco2821 with IOS12.3(14)T and CME,more than 20 local ip phones(Cisco7940) and 3 remote ip phones (Cisco7940,connected through vpn) regiested to this router.

All 7940s can call each other successfully,but only when the 3 remote ip phones dial out to PSTN,"connected" in the caller's phone screen, the called phone(include mobile phone) can receive the call,ringing,pickup the handset,but no voice can be heard.

Remote phone:extension 5297/5298/5299

Local phone:5201/5201/.....

test:

5297 dial 5298 and 5298 dial 5297,it's ok.

5297 dial 5201,it's ok.

5297 dial out to PSTN by dial "9,63912848" or "9,mobile phone number",the called phone ring,pickup,no voice.

Why?

12 REPLIES
Bronze

Re: question about remote ip phone can't dial out to PSTN

It is possible that the H323 gateway is deciding to use an IP source address on the router for voice communications that is not routable over the VPN. Try adding the following 2 commands to your voice vlan interface to ensure H323 is using an IP address routable over the VPN

(example)

Interface FastEthernet0/0.2

encapsulation dot1q 2

ip address 172.16.1.1 255.255.255.0

h323-gateway voip interface

h323-gateway voip bind srcaddr 172.16.1.1

New Member

Re: question about remote ip phone can't dial out to PSTN

thank you for reply.

But it's useless.

Re: question about remote ip phone can't dial out to PSTN

OK. First of all if my reply does not help you don't call it useless. You need to be a bit more gracious than that in this forum especially when you are asking for help. You can always give a low rating instead of being rude.

Now on to your problem. The first thing I would check is making sure that the remote subnets can ping the gateway. If they can't then you have a routing issue as the packets either don't know how to get to the gateway in the first place or don't know how to get back to the remote sites once the reach the gateway.

Hope this helps. please remember to rate all replies.

New Member

Re: question about remote ip phone can't dial out to PSTN

Thanks for your reply!

I appologize for my word in last message.I mean I had changed my configuration according jbouwkamp's instruction,but it's didn't work well.

Sorry for my poor English.

Can you explain for me that if it is the routing problem,why the remote phone can talk with local phone and dial to PSTN but no voice can be heard?

Thank you!

Re: question about remote ip phone can't dial out to PSTN

Your gateway needs to be aware of the remote sites. On the gateway try something like this.

ip route 10.0.1.15 10.0.0.20 where 10.0.1.15 is the remote site and 10.0.0.20 is the gateway that your local site uses to get to the remote site. I might be a little rusty on the command but basically the gateway has to be aware of the remote sites in order to have packets flowiing back and forth. The reason it works on the local lan and when the phones call each other is that the routing is in place properly for communication between the central site and the remote sites and of course the remote sites with itself. Give it a try and see what happens.

I understand about the language barrier. Not a problem.

Hope this helps

please remember to rate all replies

New Member

Re: question about remote ip phone can't dial out to PSTN

Thanks fou your suggestion!

I have tested that:

ip addr of remote phone 5299 is 192.168.0.247

ip addr of local gateway which is gateway of local phone is 172.16.53.251

Ping 192.168.0.247 source 172.16.53.251,successfully.

So I think maybe routing is correct.

ROUTER1#ping 192.168.0.247 sour 172.16.53.251 repe 100

Type escape sequence to abort.

Sending 100, 100-byte ICMP Echos to 192.168.0.247, timeout is 2 seconds:

Packet sent with a source address of 172.16.53.251

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

And the local gateway is the only one of the HSRP group which virtual ip address is 172.16.53.254 .There is only one router,this local gateway,in this group.

New Member

Re: question about remote ip phone can't dial out to PSTN

Hi,

On your 7940 if you press twice on i button you will call statistics. Do you have TxCnt and RXCnt increasing? If not maybe you rtp packet are not routed properly. As previously mentionned in another reply do you have those command in the router?

h323-gateway voip interface

h323-gateway voip bind srcaddr x.x.x.x

Those are their to fix rtp source address in the payload.

Pl

New Member

Re: question about remote ip phone can't dial out to PSTN

CiscoTAC told me that it's a bug :

CSCed49385

>>Externally found enhancement defect: Resolved (R)

>>encrypted ccme ephone does not handle dialpeers

>>

>>There are two work arounds:

>>

>>1) Use encrypted GRE tunnels. If the remote router is attached via a

>>GRE/IPsec tunnel, the ephone will route through the tunnel and the GRE

>>interface will pass through encryption properly.

>>

>>2) Use policy based routing to force the ephone traffic through the

>>encryptor. This can be done by placing a static route to the home ephone

>>pointing at a loopback interface, then using PBR on the loopback to set

the

>>next hop downstream of the crypto map.

>>

>>

>>Here is the topology:

>>

>>

>> ======== ================

>> | : : : CCME Router : FXO

>> home |----: home : : ######pots

>> ephone ---| : router :~~~~ IPsec : cryto head-end : peer

>> | : 831 : link ~~~~~~~~: # :

>> ======== :----------#-----:

>> : CUE # :

>> ================

>>

>>

>>With straight IPsec between the two routers, the ephone can leave

>>messages and talk to people over the FXO port. However, the ephone

>>cannot receive messages from CUE or hear caller over the FXO port.

>>

And I was told to build t GRE over IPSec tunnel to carry voice packet between remote phone and PSTN site.

I have tested h323-gateway command,it did not work well.

In deed,my question is not a one-way audio problem,caller and called can't hear each other.

I can ping to remote phone 5299(IP addr=192.168.0.247) with the source

address is gateway of local phone,so maybe routing is no problem.

IF_CHINA_ROUTER1#ping 192.168.0.247 sour 172.16.53.251 repe 100

Type escape sequence to abort.

Sending 100, 100-byte ICMP Echos to 192.168.0.247, timeout is 2 seconds:

Packet sent with a source address of 172.16.53.251

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

New Member

Re: question about remote ip phone can't dial out to PSTN

R1:Version 12.3(14)T

R2:Version 12.3(14)T2

I have tested that remote phone can dial PSTN if R2 was active voice gateway.

So I will update R1 IOS to 12.3.14T2.

New Member

Re: question about remote ip phone can't dial out to PSTN

Cisco TAC said in follow document,Cisco don't support this kind of remote call.

http://www.cisco.com/univercd/cc/td/doc/product/voice/its/cme33/cme33sa/cme33ovr.htm#wp2247785

Remote skinny client control protocol (SCCP) phones connected across WAN links are subject to the following restrictions:

–Cisco TAC will not handle any voice or signaling issues for remote IP phones, unless the same issue can be replicated for LAN phones.

But my router2 can support this kind of remote call,and I have updated router1 to IOS12.3.14T2,same as router2,I will test the remote call on router1.

Silver

Re: question about remote ip phone can't dial out to PSTN

Post back with what happens in your test - if it still does not work, you will want to check the configs line by line, maybe you have some subtle difference in your dial peer config - like 'no vad' in the working one, and not in the other. If they look the same, it might be that the dial peer matching is not happening as you expect, you should pick a quiet time so not much is going on, and turn on 'debug voip ccapi inout' and capture a good call and a bad call, and we can see the diffence between the two.

Mary Beth

New Member

Re: question about remote ip phone can't dial out to PSTN

If you have configure ip inspect than you can try:

no ip inspect name test skinny

or also if using ip nat than you can try:

no ip nat service skinny tcp port 2000

PL

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