Hello, I'm a system administrator for a group of four servers. One of these servers acts as a gateway/firewall for the other three, in addition to providing DNS, Web, and remote login services. This server has two NIC's in it. One of them is connected to a network which includes a few other machines and a bridge which connects the network wirelessly to the ISP. The other NIC is connected to a network to which the other three servers are connected. Sometimes this server becomes unreachable from outside of the local networks to which it is connected; a TCP connection cannot be established and there is no response when PING requests are sent. However, a machine on either of the two local networks can connect to this server. When this happens, I log into the server and attempt to PING the machine that it uses as its gateway (which is the router at the ISP, reached via the bridge), and I get the message "Destination Host Unreachable" from PING. But I know that the routing table on this server is correct, because it is the same one that works most of the time. In the server's ARP table, the entry for the ISP's router is incomplete. After setting the entry in the ARP table, I get no response when I ping the router. This server is running Red Hat Linux 7.1 with kernel 2.4.2-2, but I had similar trouble with Red Hat Linux 6.2 and kernel 2.2.19. The first NIC uses an RTL-8139C chip, and the second NIC is an SMC1211TX EZCard 10/100 with an RTL-8139B chip. So the 8139too module is used for both of them. For both cards the kernel prints the message "Setting 100mbps full-duplex based on auto-negotiated partner ability". Normally this machine would act as a firewall, but I don't even have the ip_tables module loaded right now, because I want to troubleshoot this problem without the firewall complicating it for now. Sometimes while the server is unreachable from the outside, I'll try to reboot it, or even halt it and then bring it back up. Normally this doesn't help, and the problem goes away as mysteriously as it came, for a day or two anyway. Can anyone suggest possible causes for this problem? I can provide full details about the system and network configuration privately to anyone who wants to help. Thank you. -- Matt Campbell <http://www.pobox.com/~mattcampbell/> - : send the line "unsubscribe linux-net" in the body of a message to majordomo@vger.kernel.org
