Hey everyone! I'm fairly new to being a network admin at a mid-sized company and I'm dealing with some pesky internet issues that I can't seem to troubleshoot effectively. We've been encountering random call drop-offs with our Mitel IP telephony system. These drops happen intermittently, which makes it really frustrating for users and a hassle for support. We're using IPSec VPN tunnels with Fortinet equipment and after checking the CPU, memory, and logs, nothing seems out of the ordinary. I've also experimented with packet captures and some basic monitoring tools, but since the issues are so sporadic, it feels like I'm always a step behind. To make matters worse, the ISP isn't very helpful, often just saying that everything looks fine. I'm eager to learn how to troubleshoot these issues better, so if anyone has recommendations for resources like books, blogs, or videos, I would really appreciate it!
6 Answers
You should definitely check out the book *TCP/IP Illustrated*. Understanding how packets behave in a network is vital for effective troubleshooting, especially since VoIP relies heavily on UDP, which complicates things further compared to TCP.
I know how you feel about the ISP saying everything's fine. Here are some suggestions:
- Monitor continuously between key points (like the firewall and VPN ends). This way, you won't miss the issue in real-time.
- Watch for jitter and brief packet loss, as they're more critical for VoIP than just bandwidth or latency.
- Path-based monitoring can also be helpful since sometimes the problem is downstream with the ISP or related to routing issues.
By the way, I work with a network monitoring tool called Obkio, and they have a free webinar coming up on June 17th that might interest you. They're covering these kinds of issues and even troubleshooting real cases live! If you're curious, you can register on their website for more details!
It might be worth segmenting your VoIP traffic into its own VLAN to prioritize it. Enabling QoS could help ensure that VoIP traffic doesn't get bogged down with other types of data on the network.
Here are a few tips that might help:
- Get familiar with the 'netstat' command, it's super handy.
- Keep tabs on your switches for issues like drops or mismatches.
- Consider installing a trial of PRTG for interface monitoring.
- Log all your dropped calls with specific details to look for patterns and potentially recreate the drop scenario.
Are you routing VoIP through your VPN? You might be experiencing too much jitter, which could be causing those call drops. Keep an eye on that!
Have you tried going back to the fundamentals of troubleshooting? Learning methods like split half troubleshooting can significantly boost your efficiency in diagnosing issues. It's all about starting from the basics.
Yeah, jitter was my first thought too. If VoIP must go through a VPN, consider using WireGuard for better performance compared to IPSec. However, it's crucial to implement proper tools for monitoring traffic flow so you can see what's really going on.