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Traffic is not forwarded through required UDP ports

Amogh Majmundar

Hi all,

I have configured t1 card for my company on a cisco 1921 router. I need to setup routes which will allow voice traffic to flow through the t1 card. Setting up routes wasn't difficult. Before this t1 card, voice traffic was going over UDP port 5060 but after I re-routed voice traffic through t1 card, the traffic is flowing through different ports. According to the phone company, UDP ports 5060-5090 is used to initiate the call so it is required that traffic flows via these ports. I checked in my network and there is not port blocking setup. The IP provider company also doesn't have any port blocking.

Before re-routing, the traffic was flowing through 5060 port. My guess is there should be some configuration needed to be done on the 1921 router. I wanted to know that am I missing something in particular or not. Any information on this would be helpful!

Thanks in advance,


7 Replies 7

Spooster IT Services
Rising star
Rising star

Hi Amogh,

Is there the following command existing on router ?

" no ip nat service sip udp port 5060 "

Spooster IT Services Team

I apologize for the delay but I checked yesterday just to make sure, and there is no command like that on router.

Hi Amogh,

Can you please add this command and see the difference?

This command is used not to change the SIP ports in case PAT is configured.

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Spooster IT Services Team

Will try and get back to you. Thanks!!

Joseph W. Doherty
Hall of Fame Master Hall of Fame Master
Hall of Fame Master

By default, changing a packet's forwarding path does not impact packet's port usage.  If a packet's ports are being remapped or blocked, there's likely something else going on beyond just using a different physical egress port.

That's what I thought. But I haven't faced issue like this before. I know some configuration needs to be done on the 1921 router. Can we force the router to forward traffic on only selected number of UDP ports?

Likely you could using PBR.

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