Crosstalk w/ SIP phones on Asterisk network


#1

Hello,
I have an Asterisk server running 1.2 with a TDM2422E, connected to a 3Com superswitch which branches out to basic hubs around the office. Into these hubs are plugged several Polycom 301, 501 and 601 SIP Phones.
Several of my users are experiencing digitized cross-talk when certain other users are on the phone at the same time (I thought that cross-talk was something I said goodbye to when I went digital, but apparently not). Can someone please advise me how to diagnose and correct this?
Thanks!


#2

To begin with, your network design should eliminate hubs and be 100% switched ports. This will stop each phone from seeing each others RTP packets unless they are specifically bound for the MAC address. All phones will still see each others’ broadcasts.

Next issue though, even if you have a bad network design that causes all packets to be layer 2 broadcasted to every device, the network stack in each device should reject packets that are not destined for its own IP. If you hear bits of other conversations you shouldn’t hear on a device, report it as a bug to that device manufacturer.

You workaround is to fix the network though to prevent the situation that exposes the device vulnerability.