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New Member

IP Phone over PIX to PIX VPN

I have a PIX 501 at home, VPN'd to the 506 at the office. My 7940 at home, comes up, and I can access data services, but I cannot place calls. The SCCP stream shouldn't be PAT'd, because data to the other network matches a nat 0 access list on both sides of the VPN. What else might be wrong, or won't this work until the 6.2 Code for PIX is release. I kind of thought it's fixes were for voip streams that actually passed through via PAT or NAT, which mine shouldn't...

8 REPLIES
New Member

Re: IP Phone over PIX to PIX VPN

Hi,

I have the same setup at home. You need to disable the skinny fixup protocol ... no fixup protocol skinny 2000.

Cisco Employee

Re: IP Phone over PIX to PIX VPN

My understanding is you only disable the skinny fixup protocol if you are not doing NAT. If you are doing nat then you need the skinny fixup. So if you are not doing nat then disable the skinny fixup. What version of code are you running on the pix 501?

Thank you,

-Mckee

New Member

Re: IP Phone over PIX to PIX VPN

Hi,

I did start a debug skinny and for some reason the pix was trying to do a fixup even with nat 0 traffic. Am I wrong to think if we use the nat 0, it should not try to do a fixup for that nat 0 traffic? I am running a beta code in a lab. I should try it out with 6.1(1)105.

New Member

Re: IP Phone over PIX to PIX VPN

Version 6.1.2 on the 501

Shouldn't be doing NAT because it should match the nat 0 list. I will try disabling skinny fixup tonight and see if that fixes it.

Bronze

Re: IP Phone over PIX to PIX VPN

I tried the same Scenario and after giving "no fixup protocol skinny 2000", it works. But can anybody explain me why ? What is the effect of this command.

Cisco Employee

Re: IP Phone over PIX to PIX VPN

The skinny fixup is only used when you are doing NAT. The Source address and Destination address is in the payload that is why you need the skinny fixup when NAT is enabled. Check out the command reference below.

http://www.cisco.com/univercd/cc/td/doc/product/iaabu/pix/pix_61/cmd_ref/df.htm#xtocid13

There is a part on the skinny fixup it self. If you are not doing NAT you just need to turn of the skinny fixup. What version of pix software were you running and what version of CCM were you running?

Thank you,

-Mckee

New Member

Re: IP Phone over PIX to PIX VPN

The document you reference indicates that TFTP is not supported via NAT at this time. i.e. if the call manager is NAT'd and the remote IP phone uses NAT to contact CM for tftp info, then it will not work. Seems like this wasn't the case prior to CM3.1.

I am trying to resolve an issue with a remote IP phone using a valid internet address and accessing the CM via a NAT'd address. I end up with one way audio. I've tried fixup both on and off, no change. I wasn't having this issue prior to CM3.1. I have been told the skinny protocol changed slightly in CM3.1 causing the issue. I have yet to find the fix. Any suggestions?

Thanks -

Lance

New Member

Re: IP Phone over PIX to PIX VPN

Forgot to respond earlier, but disabling fixup did fix the problem. Pix 6.1.2 and CCM 3.1.2c.

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