topic Re: traceroute trying to use backup lan instead of primary in Operating System - HP-UX

traceroute trying to use backup lan instead of primary

Vicki Selover — Fri, 21 May 2004 07:32:05 GMT

I have 2 network cards configured, each on a different subnet. lan0 is 100baseT and lan1 is a gigabit which is used for backing up the system. When I run a traceroute without specifying which lan, it always tries to use the gigabit card. Is there a place where this can be set to default to lan0?

Re: traceroute trying to use backup lan instead of primary

Mark Grant — Fri, 21 May 2004 07:36:23 GMT

This would be a routing issue. Check the output of "netstat -rn". Here you can see which interface is used when connecting to a specific network.

You change these with the "route" command

Re: traceroute trying to use backup lan instead of primary

Geoff Wild — Fri, 21 May 2004 07:40:26 GMT

If you are running 11.11 - then traceroute has another option - specify the interface:

traceroute -i lan0 destination

Rgds...Geoff

Re: traceroute trying to use backup lan instead of primary

Juergen Tappe — Fri, 21 May 2004 07:43:46 GMT

If you have the IP entries in /etc/hosts

i.e.:
1.2.3.4 bla.blub.com bla
5.6.7.8 bla.blub.com bla

just switch these entries so that the 5.6.7.8 will be the first and any IP access will try that first.

Re: traceroute trying to use backup lan instead of primary

Vicki Selover — Fri, 21 May 2004 07:48:14 GMT

Thanks for all the quick responses. My netstat is okay in that 192 ip uses 192 gateway and 170 ip uses 170 gateway. The traceroute works fine when I specify which lan to use with the -i option (I am on 11.11) but I don't understand why it defaults to the 192 when I don't use -i. I have the 170 in the /etc/hosts first, followed by the 192.

Re: traceroute trying to use backup lan instead of primary

Mark Grant — Fri, 21 May 2004 08:01:48 GMT

traceroute will use whichever interface is indicated by the right hand column output from "netstat -rn" for the host you are trying to traceroute to.

If you want a specific host to be accessed via a different lan, add a new route for it that explicitly says which interface. However, it will need to appear before the general route for that network. So, delete your gigabit route to the target network, add a specific host route for the host you want to traceroute to and then add your gigabit route back in again.

I imagine that doing this is going to cause you more problems than its worth though. What is wrong with specifying the interface on teh command line?

Re: traceroute trying to use backup lan instead of primary

Vicki Selover — Fri, 21 May 2004 08:11:55 GMT

Mark,
It's not a problem to specify the interface on command line. I was just concerned that regular network activity could be affected if packets are possibly trying to go out over lan1 instead of lan0. Is it possible that could happen? Everything is working okay, but I just noticed that when I ran the traceroute (before I found I had the option to do a -i), it was trying to use lan1. Sorry about my lack of network knowledge.

Vicki

Re: traceroute trying to use backup lan instead of primary

Mark Grant — Fri, 21 May 2004 08:19:41 GMT

If traceroute is going down the wrong interface, then pretty much everything else is too. Have a look at the "Ipkts" and "Opkts" fields from "netstat -in" to see which interface is being used the most. Run it a few times in succession to get a good idea.

If users should be going down the gigabit interface, then remove the other route with "route". It might be helpful to post the output of you "netstat -rn"

Re: traceroute trying to use backup lan instead of primary

Bharat Katkar — Fri, 21 May 2004 08:21:29 GMT

Try doing
# ioscan -fnC lan

Check the H/w paths. I think your gigabit is lan0 and what you are saying 100baseT could be a Management LAN.

Does your above output list both the cards. If i am right then it should only list the Gigabit Card and not that 100baseT card.

Regards,

Re: traceroute trying to use backup lan instead of primary

Vicki Selover — Fri, 21 May 2004 08:42:04 GMT

netstat -in shows both interfaces and lan0 (100baseT) is the one showing activity. lan1 has packets also from when backups have been run and I assume where the Legato server is communicating to it, but changes to those numbers are minimal. lan1 is definitely the gigabit card in slot 0/8/0/0 and lan0 is in 0/0/0/0 (L3000).

Vicki

Re: traceroute trying to use backup lan instead of primary

Mark Grant — Fri, 21 May 2004 08:44:44 GMT

Vicki,

It seems your routing table is routing network traffic down the wrong interface card. Have a look at "netstat -rn" (not "-in" this time) and post it here if you can.

Re: traceroute trying to use backup lan instead of primary

Vicki Selover — Fri, 21 May 2004 08:46:40 GMT

Here's the netstat -rn output:

Routing tables
Destination Gateway Flags Refs Interface Pmtu
127.0.0.1 127.0.0.1 UH 0 lo0 4136
170.126.4.47 170.126.4.47 UH 0 lan0 4136
192.168.0.52 192.168.0.52 UH 0 lan1 4136
192.168.0.0 192.168.0.52 U 2 lan1 1500
170.126.0.0 170.126.4.47 U 2 lan0 1500
default 170.126.1.1 UG 0 lan0 0

Re: traceroute trying to use backup lan instead of primary

Mark Grant — Fri, 21 May 2004 08:52:12 GMT

Routing tables
Destination Gateway Flags Refs Interface Pmtu
127.0.0.1 127.0.0.1 UH 0 lo0 4136
170.126.4.47 170.126.4.47 UH 0 lan0 4136
192.168.0.52 192.168.0.52 UH 0 lan1 4136
192.168.0.0 192.168.0.52 U 2 lan1 1500
170.126.0.0 170.126.4.47 U 2 lan0 1500
default 170.126.1.1 UG 0 lan0 0

Ok, If your netmask is 255.255.0.0 for each interface then any traffic going to the 192.168 network should be going through lan1.

Is this what you would expect?

Re: traceroute trying to use backup lan instead of primary

Vicki Selover — Fri, 21 May 2004 08:59:10 GMT

Mark,
That is what I would expect. My netmasks are 255.255.248.0 for lan0 and 255.255.255 for lan1.

Vicki

Re: traceroute trying to use backup lan instead of primary

Vicki Selover — Fri, 21 May 2004 09:03:35 GMT

When I run the traceroute, I get this:

Warning: Multiple interfaces found; using 192.168.0.52 @ lan1.

I would have thought if I were doing a traceroute to a 170 address, traceroute would have used lan0.

Re: traceroute trying to use backup lan instead of primary

Bharat Katkar — Fri, 21 May 2004 09:08:09 GMT

Does /etc/netconf file has entries as below and if not how they look like:

ROUTE_DESTINATION[1]=default
ROUTE_MASK[1]=""
ROUTE_GATEWAY[1]=170.126.1.1
ROUTE_COUNT[1]=1
ROUTE_ARGS[1]=""

Regards,

Re: traceroute trying to use backup lan instead of primary

Vicki Selover — Fri, 21 May 2004 09:19:28 GMT

Here are the entries:
Is my problem that the broadcast is specified for lan1 as the 192 network and it's not specified for lan0?

Vicki

INTERFACE_NAME[0]="lan0"
IP_ADDRESS[0]="170.126.4.47"
SUBNET_MASK[0]=255.255.248.0
ROUTE_GATEWAY[0]="170.126.1.1"
ROUTE_COUNT[0]="1"
ROUTE_DESTINATION[0]="default"

INTERFACE_NAME[1]="lan1"
IP_ADDRESS[1]="192.168.0.52"
SUBNET_MASK[1]="0xfffff800"
BROADCAST_ADDRESS[1]="192.168.0.255"

Re: traceroute trying to use backup lan instead of primary

Mark Grant — Fri, 21 May 2004 09:22:25 GMT

I have to say, your subnet/broadcast addresses look wrong to me though I can't quite get my head to gether to tell you why!

Re: traceroute trying to use backup lan instead of primary

Bharat Katkar — Fri, 21 May 2004 09:25:53 GMT

Not sure but try changing this entry:

SUBNET_MASK[1]="0xfffff800" to

SUBNET_MASK[1]=255.255.248.0

Then do

/sbin/init.d/net stop
/sbin/init.d/net stop

Hope that works.

Regards,

Re: traceroute trying to use backup lan instead of primary

Vicki Selover — Fri, 21 May 2004 09:27:09 GMT

Good thing it's Friday then Mark! I didn't mean to be such a pain on the first question I've ever posted!!