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тАО08-18-2012 01:16 AM
тАО08-18-2012 01:16 AM
Different subnet's IPs are routing server's own IP
Hi All,
I have a strange problem in my HP-UX 11.31 box. When I use traceroute command for an IP of different subnet than it's own, the trace ends up on it's own IP:
# traceroute 172.20.11.1
traceroute to 172.20.11.1 (172.20.11.1), 30 hops max, 40 byte packets
1 agbdb (172.22.25.11) 0.077 ms !N 0.029 ms !N 0.011 ms !N
I have tried deleting the IP and resetting it after restart. The gateway setting is also present in the server. Default route is also present in the routing table:
default 0.0.0.0 172.22.25.1 Yes lan0
All these same settings are working fine on other servers. But traffic on this server ends up on it's own IP.
Why is the traffic not moving out from the it's network card? What can be the issue?
Regards,
Taurian.
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- traceroute
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тАО08-18-2012 07:49 PM
тАО08-18-2012 07:49 PM
Re: Different subnet's IPs are routing server's own IP
You're probably better off asking this in the HP-UX forum instead of the HP Networking forums, but if you post the output of 'netstat -in' and 'netstat -rn', we can probably point you in the right direction.
Paul
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- netstat
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тАО08-19-2012 12:03 AM
тАО08-19-2012 12:03 AM
Re: Different subnet's IPs are routing server's own IP
Hi Paul,
Thanks for your reply.
Following is the output from a server that is NOT working:
# netstat -in
Name Mtu Network Address Ipkts Ierrs Opkts Oerrs Coll
lo0 32808 127.0.0.0 127.0.0.1 12305 0 12305 0 0
lan0 1500 172.22.25.0 172.22.25.11 118016 0 11609 0 0
# netstat -rn
Routing tables
Destination Gateway Flags Refs Interface Pmtu
127.0.0.1 127.0.0.1 UH 0 lo0 32808
172.22.25.11 172.22.25.11 UH 0 lan0 32808
172.22.25.0 172.22.25.11 U 2 lan0 1500
127.0.0.0 127.0.0.1 U 0 lo0 32808
default 172.22.25.1 UG 0 lan0 1500
Following is the output from a WORKING server:
# netstat -in
Name Mtu Network Address Ipkts Ierrs Opkts Oerrs Coll
lan0 1500 172.22.25.0 172.22.25.19 378832 0 278590 0 0
lo0 32808 127.0.0.0 127.0.0.1 17816 0 17816 0 0
lan0:131 1500 172.20.24.0 172.20.24.23 120 0 0 0 0
Warning: The above name 'lan0:1316887' is truncated, use -w to show the output in wide format
# netstat -rn
Routing tables
Destination Gateway Flags Refs Interface Pmtu
127.0.0.1 127.0.0.1 UH 0 lo0 32808
172.20.24.23 172.20.24.23 UH 0 lan0:1316887 32808
172.22.25.19 172.22.25.19 UH 0 lan0 32808
172.20.24.0 172.20.24.23 U 3 lan0:1316887 1500
172.22.25.0 172.22.25.19 U 3 lan0 1500
127.0.0.0 127.0.0.1 U 0 lo0 32808
default 172.22.25.1 UG 0 lan0 1500
Regards,
Taurian.
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тАО08-19-2012 01:36 AM
тАО08-19-2012 01:36 AM
Re: Different subnet's IPs are routing server's own IP
I'm not exactly sure about how HP-UX responds to ICMP redirects or connection refusals, but my guess is that one or other of those is preventing your host from getting through. What does the traceroute output look like on both servers?
Paul
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тАО08-20-2012 05:34 PM
тАО08-20-2012 05:34 PM
Re: Different subnet's IPs are routing server's own IP
Hi Paul,
Traceroute from NOT working server:
# traceroute 172.20.11.1
traceroute to 172.20.11.1 (172.20.11.1), 30 hops max, 40 byte packets
1 agbdb (172.22.25.11) 0.077 ms !N 0.029 ms !N 0.011 ms !N
Traceroute from WORKING server:
# traceroute 172.20.11.1
traceroute to 172.20.11.1 (172.20.11.1), 30 hops max, 40 byte packets
1 172.22.0.5 (172.22.0.5) 1.220 ms 0.711 ms 0.707 ms
2 172.22.5.242 (172.22.5.242) 0.789 ms 0.736 ms 0.726 ms
3 172.22.0.9 (172.22.0.9) 8.847 ms 9.829 ms 9.918 ms
4 8.8.8.2 (8.8.8.2) 44.848 ms 45.020 ms 44.818 ms
The thing is that I have already reinstalled HP-UX from DVD in exactly the same manner as I did the working servers. The issue still exists. This eliminates any issues at HP-UX's end.
Reagrds,
Taurian.
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тАО08-20-2012 08:03 PM
тАО08-20-2012 08:03 PM
Re: Different subnet's IPs are routing server's own IP
Those traceroutes are hitting a different router for the same destination. I've just realised that your netstat -rn output did not include any netmasks. If you can find the flag on HP-UX which shows the mask for each route and repost the netstat -rn output, we should be able to pinpoint what's happening. Do the HP-UX boxes run any dynamic routing daemons such as ripd or quagga?
Paul
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тАО08-21-2012 02:51 AM
тАО08-21-2012 02:51 AM
Re: Different subnet's IPs are routing server's own IP
> 1 agbdb (172.22.25.11) 0.077 ms !N 0.029 ms !N 0.011 ms !N
The !N in the traceroute output means that a "network unreachable" error was generated.
Does the gateway 172.22.25.1 answer to pings? If not, have you disabled the Dead Gateway Detection function of HP-UX?
By default, HP-UX tends to expect that gateways should answer to pings, and if they don't, HP-UX assumes the gateway has failed and marks the gateway entry in the routing table as disabled. That would explain the "network unreachable" error generated at the sending host itself: the host thinks it has no valid gateway for sending to the specified destination, so it has no choice but to generate error responses.
To disable Dead Gateway Detection, you'll need to change a ndd setting:
ndd -set /dev/ip ip_ire_gw_probe 0
To make the setting persistent, edit /etc/rc.config.d/nddconf.
After switching off Dead Gateway Detection, you may need to delete the default gateway entry from the routing table and add it back to re-enable it. (Unfortunately the "netstat -rnv" output does not indicate whether any gateways listed are disabled by DGD or not.)
> If you can find the flag on HP-UX which shows the mask for each route and repost the netstat -rn output,
The command for that is "netstat -rnv".
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