SIP problem with UC500

Answered Question
Jul 23rd, 2009

Hi!

I've installed a UC520-16U with 10 phones at a customer. They have an ADSL connection with a Intertex IX78 modem that's sip compatible.

Outgoing calls works like a charm every time, but all incomming calls fail. My SIP provider tells me that they can't find my UC500, so incomming calls is'nt directed at all. It's the modem that get's in the way according to them.

After a long call to the modem manufactor the ask me to upgrade and try again. At this point we see increased activity in the modems sip logs and it seems that my provider is able to reach the UC500 but still no calls come's through.

Where is the problem?

I have attached both the TAC log from the UC and SIP log from the Intertex modem.

Thanks!

I have this problem too.
0 votes
Correct Answer by Maulik Shah about 7 years 4 months ago

I think the first issue is your modem should not be responding to any SIP messages on its own. Is there anything you can set on the modem to disable SIP lookup and just allow transparent passthrough of the SIP messages (i.e. UDP port 5060) to the UC520 WAN IP address? No recommendation on any DSL modem - as long as it transparently passes SIP traffic through to the UC520 should work.

Couple of things that you could do:

- ensure UC520 always uses port 5060 as the source port for all SIP traffic:

sip-ua

  connection-reuse

- if the SP uses different source IP addresses for SIP messages to and from the UC520 - ensure you add them in per the below

https://supportforums.cisco.com/docs/DOC-9830

Correct Answer by Saurabh Verma about 7 years 4 months ago

Hi Markus,

I looked through the logs, and it appears that the Intertex modem is taking the request from UC500 and passing it along to the provider fine. For example, I tracked the registration of 0545577299 which was sent out by UC500 at 11:41:59. The modem creates a proxy entry for this with its own IP address and this translation works good (there is a challenge from the provider which is passed over to the UC500 and gets responded back). With this SIP REGISTER message, 0545577299 gets registered with the provider.


Later in the logs, I also noticed that the SIP provider tried to place a call to 0545577299 (at 11:43:) , however, the Intertex modem challenged this invite and sent back a 407. I don't think this is the correct procedure. The invites from the SIP provider should be passed on to the UC500 without a challenge. Can you check with the Intertex modem folks to see if this can be disabled?

Thanks,

Saurabh

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Correct Answer
Saurabh Verma Thu, 07/23/2009 - 06:53

Hi Markus,

I looked through the logs, and it appears that the Intertex modem is taking the request from UC500 and passing it along to the provider fine. For example, I tracked the registration of 0545577299 which was sent out by UC500 at 11:41:59. The modem creates a proxy entry for this with its own IP address and this translation works good (there is a challenge from the provider which is passed over to the UC500 and gets responded back). With this SIP REGISTER message, 0545577299 gets registered with the provider.


Later in the logs, I also noticed that the SIP provider tried to place a call to 0545577299 (at 11:43:) , however, the Intertex modem challenged this invite and sent back a 407. I don't think this is the correct procedure. The invites from the SIP provider should be passed on to the UC500 without a challenge. Can you check with the Intertex modem folks to see if this can be disabled?

Thanks,

Saurabh

m.junghage Mon, 08/03/2009 - 01:33

Thank you for your reply!

I've spoken to the modem manufactor and they can't give me any support at the moment because they hav'nt tested the UC500 with my SIP provider. Is there any adsl modem that I can replace the Intertex with and make it work?

I've found a similar problem on uc500.com, could it be this simple?

"Had this same error, then I realized the UC500 config assistant sets up by default an ACL on the WAN port that doesnt allow SIP traffic through, and doesnt change it when you configure a SIP trunk. Go figure.
You need to open TCP/UDP ports 5060-5080."

Thank you for all your help.

Eivind Jonassen Mon, 08/03/2009 - 02:19

Markus,

If you use CCA2.0 this shouldn´t be a problem. Have you checked your config to be on the safe side?? Probably access-list 104 for your WAN interface, atleast if you use the default config on the UC

Regards

Eivind

Correct Answer
Maulik Shah Mon, 08/03/2009 - 09:32

I think the first issue is your modem should not be responding to any SIP messages on its own. Is there anything you can set on the modem to disable SIP lookup and just allow transparent passthrough of the SIP messages (i.e. UDP port 5060) to the UC520 WAN IP address? No recommendation on any DSL modem - as long as it transparently passes SIP traffic through to the UC520 should work.

Couple of things that you could do:

- ensure UC520 always uses port 5060 as the source port for all SIP traffic:

sip-ua

  connection-reuse

- if the SP uses different source IP addresses for SIP messages to and from the UC520 - ensure you add them in per the below

https://supportforums.cisco.com/docs/DOC-9830

m.junghage Thu, 08/06/2009 - 12:15

Thank you all for your help!

After talking to my service provider I replaced the Intertex modem with a regular modem (Zyxel P-660HW) and it worked like a charm! The problem was caused by the Intertex modem interfering with sip traffic as it's trying to act as a sip gateway.

Since the dsl provider only gives out one public ip the uc500 can't be assigned a public ip. Is there any downsides on the telephony side by doing this?

Thanks!

Marcos Hernandez Thu, 08/06/2009 - 13:11

Yes, there is a big downside, you will experience one way audio. You need an upstream device that implements ALG (Application Layer Gateway) which is a specific form of application-aware NAT. The requirements are described in the document "Integrating the UC500 into an existing Network" on:

https://supportforums.cisco.com/docs/DOC-9674

Thanks,

Marcos

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