Hey everyone! I'm new to being a network admin at a mid-sized company, and I've been facing some really annoying Internet issues. We're experiencing random call drop-offs with our Mitel IP telephony system. The drops aren't consistent, which makes it tricky to figure out and frustrates our users. We're using IPSec VPN tunnels along with Fortinet gear, and I've looked into CPU/memory and logs, but nothing stands out as a problem. I've also tried using packet captures and some free monitoring tools, but the intermittent nature of the issue means I often feel like I'm too late when I check. The ISP isn't helping much either; they keep saying everything's fine after their tests. I'm looking for advice on how to troubleshoot these problems better, so if anyone has good resources like books, blogs, or videos, I would really appreciate it!
5 Answers
Have you considered starting with the basics of troubleshooting? Learning techniques like split-half troubleshooting can really enhance your overall effectiveness when diagnosing network issues.
Familiarize yourself with the netstat command and your network switches. Look for any drops or mismatches. You might also want to trial PRTG to monitor your interfaces, assuming SNMP is supported. Keep a log of the dropped calls with details to identify any patterns.
I feel you on the ISP frustrations! Here are a few tips that may help:
- Continuously monitor key points in your network (like between your firewall and VPN endpoint) to catch issues more easily.
- Look out for jitter and packet loss spikes, which matter much more in VoIP than just overall bandwidth.
- Path-based monitoring could reveal problems not related to your equipment, like ISP peering issues or congestion.
I also use a tool called Obkio for network monitoring, and we're hosting a free webinar on troubleshooting these kinds of issues soon. Might be worth checking out for more hands-on help!
Are you running VoIP over your VPN? That could lead to issues like jitter, which would explain the drop-offs you're seeing. It's worth looking into the specifics of how you're routing that traffic.
You should definitely check out 'TCP/IP Illustrated.' The first half of the book is great for understanding how packets operate, which is crucial for troubleshooting. Keep in mind, VoIP mainly uses UDP, making it trickier to diagnose than TCP issues.
I thought the same thing. If you have to route VoIP through a VPN, using something like WireGuard might give you better performance than IPSec. Beyond that, proper flow monitoring tools can really help you identify the issue.