Cisco Voice HELP

J 19101919
J 19101919 used Ask the Experts™
Hi All,

We currently have an issue with a new build at a remote site.

The overall voice network is fully working at other locations, however the new site is having issues with inbound calls from the PSTN. The phones at both ends (internal and external) will ring, however no audio is passed. The call remains open, but silent.

Calls work outbound from the site successfully. The CUCM/Cube are on the main site, where calls work fine. The remote site is connected to the main network over a site to site VPN.

The only difference between this and other sites is the allocated IP range. The Cisco phones on the remote site are all using public IP addresses, where the main network and other remote sites are utilising private address space.

Any thoughts or suggestions would be greatly recieved.

Many Thanks,

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Distinguished Expert 2018

It sounds like an issue involving firewall rules, and some necessary ports not being open to let the right traffic enter. My big concern however would be why the phones at most sites have public IP addresses...
I agree with masnrock. Just put the phones behind the firewall and configure that network as part of the VPN tunnel.



Sorry I might not have been clear in my description, we've allocated public addresses to the devices, however these are behind a firewall, with interesting traffic (cube/call server etc) heading over the VPN.

Calling can be established locally and inter site with no issues. Outbound calls to the pstn network are fine.

External calls being received from the PSTN are the issue. Phones ring, call connects and stays open, no audio though either way.


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Distinguished Expert 2018

Are there any traffic restrictions between the two networks?



Not that I'm aware of, I don't have control over the main site, however both sides of the vpn have been setup identically allowing the relevant interesting traffic.

What's weird is most calls work fine. Inter-site works fine. Internal (remote site) to External PSTN works fine. It is purely recieving the External PSTN to internal on remote site that has no audio. The calls ring and can be answered, just no audio is passed.

External PSTN to main site is fine.
Distinguished Expert 2018
Yeah, you may want to want to do some packet capturing with something like Wireshark. It's clear that there is traffic that isn't getting to where it's supposed to. More of a question of whether that problem is at the main site, remote site, or somewhere in between.

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