Stability Issues w/ Certain IP Ranges

[cybermonk]

Hi there,

I just spent 45 minutes on the phone with a support tech and we were unable to resolve this issue, so I was directed to try posting about it here while my support ticket is bumped up the line to the network folks.

In a nutshell: I'm experiencing stability issues of some kind on my line, but only when I have an IP in a range other than 70.x.x.x. While general browsing works fine, there are definitely connectivity issues present, as a persistent IRC client connection I run on my home server cycles its connections every 5-10 minutes (resulting in a barrage of connection information pings), and I notice short drops in AIM/GChat connectivity as well. This only occurs on ranges other than 70.x.x.x; recently, I've been receiving IPs in the 173.228.x.x and 50.0.x.x ranges instead.

This has actually been an issue for a long time (I've noticed it whenever my IP changed to something outside 70.x.x.x), but in the past I'd always been able to cycle my modem and receive an IP in the latter range, which has fixes the stability issues. I'm aware that it's strange that a different IP range would cause this, but it's really the only thing I can definitively link to the issues I'm experiencing. Nothing else in my home setup has changed, and this only really became an issue when I recently was unable to reacquire an address in the "working" range.

My current IP is 173.228.119.100. I'd be glad to offer any other information as needed. Thanks for any help!

[cybermonk]

Just a quick note: I've since reacquired an address in the working range, 70.36.134.137, and have confirmed that the previously present stability issues are now gone, as expected. I'm still interested in figuring out what's going on, however, as this is only a solution so long as I can keep this new IP.

[dane]

We think we know what this is: firewalling of DHCP unicast lease packets. The initial DHCP lease is issued via broadcast, and is five minutes. The lease renewals are unicast between your system and the DHCP server, so if you're seeing a failure every 5-10 minutes, it's likely a failure to renew the lease for your IP.

Do you have any PC or router firewalling in place? If so, can you disable it and see if the issue is resolved?

-Dane

[cybermonk]

Thanks very much for the response! I checked and did notice that the SPI firewall was enabled on my router (I use DD-WRT), so I've disabled that. As I have an IP in the "working" range currently, I can't tell whether this will fix the issue, but I'll be sure to report back here with finding if/when the IP on the modem cycles.

[bobrk]

It's interesting that your IP address cycles so much. Mine never changes unless I change my router, which happened a few months ago. But between those very rare occurrences, it never changes. It's almost like having a static IP.

[cybermonk]

This has been my experience in the past, and normally the modem doesn't change IPs (I wouldn't be surprised if this 70.36.134.137 address I now have is the same that I've usually had during most of my time with Sonic). However, occasionally, the modem drops it connection and when I power cycle it, it comes back with an IP in one of the ranges mentioned above.

[kgc]

If the modem/firewall is not being rebooted on a regular basis, it's probably a symptom of the real problem. The firewall is breaking unicast DHCP causing the dhcpclient to fall back to a full DHCP discover cycle. A system will loose connectivity through this process and it is possible that your IP would change.