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01-05-2008, 09:52 AM
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 strange routing issue Hi, I get the strangest routing problem on a single AIX 5.2 ML4 server: 1. problemserver cannot ping a particular host x.x.x.55 which is on the WAN. 2. problemserver can ping all other servers on the LAN and WAN including x.x.x.66 which is in the same room as x.x.x.55 (and has the same default gateway as x.x.x.55). 3. x.x.x.55 cannot ping problemserver. 4. x.x.x.66 can ping problemserver. 5. 3 of about 70 servers on the WAN cannot ping problemserver. They have different default gateways. 6. problemserver has not had any local changes recently. The big change in the environment was to perform a DR, so some network isolation occurred. The network guys are extremely adamant that this issue is not on their side, and the problem is not occurring anywhere else afaik. Before rebooting, what could I check other than stale ARP entries? Regards, Niel      |
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01-05-2008, 09:52 AM
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| Re: strange routing issue Niel Lambrechts wrote: > Hi, > > I get the strangest routing problem on a single AIX 5.2 ML4 server: > 1. problemserver cannot ping a particular host x.x.x.55 which is on the WAN. > 2. problemserver can ping all other servers on the LAN and WAN including > x.x.x.66 which is in the same room as x.x.x.55 (and has the same default > gateway as x.x.x.55). > 3. x.x.x.55 cannot ping problemserver. > 4. x.x.x.66 can ping problemserver. > 5. 3 of about 70 servers on the WAN cannot ping problemserver. They have > different default gateways. > 6. problemserver has not had any local changes recently. > > The big change in the environment was to perform a DR, so some network > isolation occurred. > > The network guys are extremely adamant that this issue is not on their > side, and the problem is not occurring anywhere else afaik. > > Before rebooting, what could I check other than stale ARP entries? > > Regards, > Niel I too am having considerable difficulties with routing on AIX 5 and am about to post two questions. One observation that I had was that after one of two AIX 5.3 machines was powered off for a few days and back on again, the other one had static routes for its a-lan pointing at its b-lan, and its b-lan pointing at its a-lan. I had to delete those two entries before I could talk to the machine. It may pay to check your routing table carefully (netstat -r) in case some nasty static routes have been added automatically. One other possibility that I've hit in the past with 10/100Mbit networks (and maybe this continues for 1GB too) is having a speed/duplex mismatch between the machine (lsattr -El ent0 | grep speed) and the Switch port that it's connected to. If the Switch port is set for auto-negotiate and the machine's port is set to 100Mbit full duplex, the Switch will often decide to use 100Mbit HALF duplex, with a crippling result in network performance (which will likely be invisible to network administrators). Best wishes, Jeffrey. |
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