Section 11.1. VoIP Troubleshooting Tools

Here's what you'll need to troubleshoot a VoIP network:

A softphone, because softphones tend to be easier to configure than hardphones. They also provide more useful logging output. Xten Network's SIP softphone with logging output is available free from their web site (http://www.xten.com). A free H.323 softphone with logging output is OhPhone
A packet sniffer such as Ethereal, which runs on several platforms. It's available at http://www.ethereal.com. Snort can be useful for troubleshooting security issues, too
If you're troubleshooting from behind a firewall, you'll need access to an unfirewalled public IP address, too. SIP can be stymied by NAT firewalls (more on this later)
A SIP server like SIP Express Router (http://www.iptel.org/ser) or a SIP-compatible registrar like Asterisk or VOCAL. In this book, we've used Asterisk. For H.323 setups, a free gatekeeper and gateway like those included in Open H.323 are recommended