Shawn Grover wrote:
At the last meeting I had asked for any tips on dealing with a connectivity issue I was having. My Gentoo server and workstation installs would periodically loose their connection to the internet. To restore connectivity, I had to ping the external IP address of my firewall. It was suggested to look into icmp and upmp, but other than that I think I stumped the crowd.
I have found a solution, though I don't think it's the "right" solution as it doesn't address or identify the root cause of the problem. It turns out that when I have lost connectivity, my ARP cache is empty (doing "arp -n" or "arp -a" at the command prompt displays your cache). ARP is used to map the network card's MAC addresses to an IP address, which is required for TCP/IP over ethernet. When I have a connection, I have an ARP entry to my firewall's internal IP address. So, as a work around, I wrote out the entry when I had a connection, then did the following command:
arp -s 192.168.0.1 ff:ff:ff:ff:ff:ff
(Where the ff:ff:ff:ff:ff:ff is the MAC address I wrote down).
This adds a permanent entry (well, until the next reboot) into the arp
cache. Once I did this, I didn't loose my internet connection at all.
Now, as I said, this doesn't resolve the core problem - why am I loosing the arp cache entry? I've done some digging on this, and it is sometimes caused by duplicate IP addresses on the same network, or assigning the subnet broadcast address to a device. That's not the case on my network though. So I'm still looking (though not quite as hard anymore). I thought I'd post here to let those who tried to help know I found a solution, and to possibly help anyone who may run into a similar problem (my research indicated similar issues on other platforms).
Shawn
