Multi-IP routing problem?

[Phil Daws_3]

We have a HP9000 N-Class that has two 4xport NICs in it. Only one off the interfaces has a real IP address allocated to it. The other IPs are virtual ones. All was working fine until the server was rebooted over the weekend. We now have a situation where some networks can get to the virtual IP and others cannot. After a few hours the problem fixed itself and traffic was flowing again from all networks. The Networks team say there is not problem on their switches but I cannot understand why some networks can route and others cannot. Could this be something to do with the ARP registration on the core Cisco switches?

[Ron Kinner]

Seems unlikely. If one remote network is able to get to you then the switch apparently knows you are there. If it happens again you can test the switch with a linkloop test. (see the man for details). Be sure and specify which interface you want it to use. You will need to know the MAC of another device on the switch (in the same vlan). After you talk to a device you can do
arp -a
to see the MAC.

My bet would be a routing problem somewhere. traceroute would be the best way to check. Do one from each end and see where it stops. (You should probably do one now while it still works so that you will know for sure that traceroute works. Sometimes the reponse is turned off by the network admin.) Also do a
netstat -rn
now to see what your routing table looks like when it works.

Ron

[Phil Daws_3]

May have found what is causing the problem - but if not it needs fixing ! Somebody had assigned the same Virtual IP address, using multiipconf, to two different machines. Therefore the same IP was being presented against two different MAC addresses! DOH!

[Tor-Arne Nostdal]

There is a possibility to "create" an error in the startup files, if some of the /etc/rc.config.d/hp{interface}conf files is manually edited and use the variable HP_{interface}_STATION_ADDRESS[i]={MAC-address}

See if MAC-address is hardcoded in some of these files:
grep STATION_ADDRESS\\[.\\]=0x /etc/rc.config.d/*

Some handy commands to check MAC-addresses, interfaces in use, drivers (appropriate config file)

lanscan
netstat -i
ioscan -fk | grep -i lan

[rick jones]

indeed assigning the same IP address on two separate machines can lead to poor results...

...if it is done for load balancing, on HP-UX, one assigns the VIP to the loopback interface (lo0:1, lo0:2 etc) not a "real" (from the standpoint of the transport) interface