How to capture SIP frames with Ethereal

Posts: 3 · New Forum Member Joined: May 07, 2005 Posts: 3

I have Vonage service at home and want to learn more about SIP. I have worked on Voip projects before but they were based on MGCP. My problem is I can not see any SIP frames on the network. Here is my configuration.

SB2400 Surfboard Cable Modem --> Linksys WRT54G Router -->
Linksys EAFH05W Hub --> VT1000 Voice Terminal
|-------> PC running Ethereal

In all my setup, I am using RJ45 interface. I have removed the router to lessen the complexity but it did not help. I saw in this forum people were able to capture SIP frames.

Posts: 1424 · Posted: Sat May 07, 2005 3:33 pm Post subject:

You need to connect your PC to the Linksys EFAH05W Hub in order to see the packets. If your PC is connected to the VT1000's LAN port it can not see the traffic between the adapter and Vonage.

Posts: 3 · New Forum Member Joined: May 07, 2005 Posts: 3

Thanks for your replay. The PC is connected to the HUB along with the VT1000. The graphical presentation did not come out the way I wanted in my fist post.

So the setup is without the router: Cable Modem goes into the HUB port 1. HUB port 2 goes to the VT1000. And HUB port 3 is connected to my PC. I think this should do it. But I still do not see SIP or RTP packets.

I have checked the HUB runs at 100Mbps at all ports. I read some place that if an auto-sensing port runs 100Mbps on one port and 10Mbps on another, packets may not be replicated between them. But this not the case.

Also, I am running Ethereal in promiscuous mode. So, this should not be problem either. I know I am missing something simple but I do not know what.

Posts: 59 · Full Forum Member Joined: Dec 16, 2004 Posts: 59

Are you able to see any packets to/from the VT100 in your ethereal trace?

Posts: 1424 · Posted: Sat May 07, 2005 8:45 pm Post subject:

My research turned up the following link [Ethereal-users] Hub model numbers that work with Ethereal that is a user report claiming that your hub, the EFAH05W, doesn't work with ethereal.

I was somewhat skeptical, but I found other similar references. I am afraid you may be out of luck with that hub (switch?).

Posts: 3 · New Forum Member Joined: May 07, 2005 Posts: 3

SUCCESS!!

Thanks scerruti... Just used Netgear DS104 hub instead of Linksys EFAH05W. I am seeing both SIP and RTP packets now.

I had pay $50 for a hub when I know I can get a switch for a lot less. But I needed a "real hub/repeater".