On Wed, 2 Jan 2002, Chad Morgan wrote: > > eth0 Link encap:Ethernet HWaddr 00:A0:CC:23:A3:AC > inet addr:216.86.213.93 Bcast:216.86.213.255 Mask:255.255.255.0 > UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 > RX packets:241367 errors:0 dropped:0 overruns:0 frame:0 > TX packets:260291 errors:0 dropped:0 overruns:0 carrier:0 > collisions:41 txqueuelen:100 > Interrupt:10 Base address:0x6000 > > eth0:1 Link encap:Ethernet HWaddr 00:A0:CC:23:A3:AC > inet addr:216.86.213.94 Bcast:216.86.213.255 Mask:255.255.255.0 > UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 > Interrupt:10 Base address:0x6000 >
<snip> > > Kernel IP routing table > Destination Gateway Genmask Flags Metric Ref Use > Iface > adsl-gte-la-216 * 255.255.255.255 UH 0 0 0 > eth0 > adsl-gte-la-216 * 255.255.255.255 UH 0 0 0 > eth0 > 192.168.0.0 * 255.255.255.0 U 0 0 0 > eth1 > 216.86.213.0 * 255.255.255.0 U 0 0 0 > eth0 > default adsl-gte-la-216 0.0.0.0 UG 1 0 0 > eth0 > > Note: the the first two entires are the hosts associated with eth:0 and > eth0:1 > > Now, I'm a remote location but when logged into this machine I can ping all > ip addresses. > > >From my machine I get no responce when I try and ping the address > associated with eth0:1 however when I use tcpdump host 216.86.213.94 I get > the following result while pinging that address from my machine so it looks > like it is getting something but not answering. > > 11:31:07.232889 ca-brea2a-102.stmnca.adelphia.net > > adsl-gte-la-216-86-213-94.mminternet.com: icmp: echo request (DF) > Chad, It sounds like you've fallen prey to the perils of assymmetric routing. For simplicity, I'll refer to your ("my machine") external server to be machine A, eth0 to be ip-address B, and eth0:1 to be ip-address C. Here is how things are happening : Machine A sends echo request to C. C replies. The routing table on your multihomed server says that the packet needs to travel out via eth0. The outgoing echo reply therefore will contain the source address of B. A is not listening for replies from B. It is listening for replies from C. Hence your problem. To see if I am right, filter tcpdump on the icmp protocol, rather than the host of C. If you see echo replies from B coming in, and echo requests for C going out, what I said is correct. Regards, Jor-el