Can't traceroute out of network - stange circumstances

[Alan Schunemann]

Hi,

I have two servers on the same network at an ISP (NT & HPUX 11.0). I can VNC to the NT system and telnet to the HPUX system. I cannot access the HP system from the outside. (I could a last night) I cannot traceroute from the HPUX system to other systems outside the network. (!N's in traceroute) I can't ping the gateway but I can traceroute to it. (one hop, very strange) On the ISP's telnet server (Linux) on the same network, I can traceroute out but can't ping the gateway either. I think I've run into this problem before. Is it an HPUX-ism? Any thoughts? My guess is that I need to restart the router. Thanks!

[harry d brown jr]

Are the routers allowing pings and traceroutes? Also, do you have a default route on your HP?

[Stefan Schulz]

Often routers are configured not to answer on ping requests. This is to protect them against DoS attacks.

As you can traceroute out from the Linux box, i think the problem is somwhere on your HP-UX box. The router seems to be ok, as you can traceroute out from this network.

I would go for the HP-UX box, not the router.

Hope this helps

Regards Stefan

[Volker Borowski]

Alan,

most likely it is one of four possibilities:
- no default GW set
- default GW is set, but without a hopcount of 1 (HPUX is sensitive to this one missing!)
- the netmask on the NIC of the HP UX does not match the subnet
- Access to the HP is blocked in a firewall

Hope this helps
Volker

[harry d brown jr]

Alan,

do a "netstat -rn", and tell us what it is saying. You should have one entry like this:

default 141.123.224.1 UG 0 lan0 0

where 141.123.224.1 is your router (default gateway)

[Alan Schunemann]

I have my default gateway set. The system was running fine for over 30 days and then I couldn't access it from the outside. Also, if I remove the default route and then try to add it back, it says, "network unreachable."

[harry d brown jr]

I'm wondering if you need to flush your arp table, on both your HP and your router. Sotty, but I'm brain dead this morning, and I forgot how to on the HP, as for the router, give it a quick kick :-)

harry

live free or die

[Alan Schunemann]

Ok. This morning, I deleted the default route and added it again and it worked! Last night, when I tried this, it said, "network unreachable."

[harry d brown jr]

Is your HP server now available from the outside?

harry

live free or die

[Alan Schunemann]

It just stopped working again! It's obviously something on their end.

[harry d brown jr]

Don't you hate it when you spend so much time just to find out its the fools on the other end? Time to slap them around I guess!

harry

live free or die

[Alan Schunemann]

Update. If I delete and add the default route it works for a few minutes. (I'm logged in from a telnet session from a VNC connection on a NT system on the same network)

[Brian Hackley]

Hi,

This one caught my eye. Very interesting.
Just a guess:

See ITRC Application Note: KBAN00000750
Dead Gateway Detection

To disable Dead Gateway Detection:

ndd -set /dev/ip ip_ire_gw_probe 0

Hope this helps!!

-> Brian Hackley

[Alan Schunemann]

Thanks Brian. I believe it's:

ip_ire_gw_probe_interval (read and write)

I'm trying it now.

[Alan Schunemann]

The ip_ire_gw_probe_interval is currently set to 180000. When I try to set it to 0, I get an error:

wksta1_root 34: ndd -get /dev/ip ip_ire_gw_probe_interval
180000
wksta1_root 35: ndd -set /dev/ip ip_ire_gw_probe_interval 0
operation failed, Invalid argument

[IT Response]

The correct command to resolve the problem is:

ndd -set /dev/ip ip_ire_gw_probe 0

By default, if the server cannot detect a gateway by pinging it) within 5 minutes, the gateway is declared to be "dead".. To avoid this, use the command above.

[Alan Schunemann]

HP Resource Center,

Did you read my previous post about the incorrect format of the ndd command. I copy-pasted your command and received the following response:


wksta1_root 21: ndd -set /dev/ip ip_ire_gw_probe 0
name is non-existent for this module
for a list of valid names, use name '?'

[Alan Schunemann]

How do I set the ip_ire_gw_probe_interval to "never"? 0 does NOT work:

ndd -set /dev/ip ip_ire_gw_probe_interval 0
operation failed, Invalid argument

Thanks,
Alan

[Alan Schunemann]

It looks like I need patch PHNE_20436 to get the ip_ire_gw_probe parameter.

[Alan Schunemann]

My ISP fixed the router so I can ping it. Problem resolved. Thanks to everyone for their help!