default gateway stops working some time after a reboot

[David Connolly]

Hi

Bizarre scenario here. I have a HPUX 11.11 system whose default gateway seems to stop working some time (still to be determined) after a reboot.

The system is a web server sitting behind a firewall, with the inner port of the firewall set as the default gateway. I can browse to the web site without issue from the local LAN.

If I reboot the system, I can browse to is from the internet without difficulty. However after a short while (< 2hours, but I'm not sure exactly how much less) the site stops responding from the web, yet is still available from the local LAN.

If I add a static route to the public address using the same address as the default gateway, the site responds again. Netstat -r shows that the default gateway is still set to 192.168.1.100.

I would appreciate any advice on where to start looking for this.

Attached is my netconf - note the number of logical IP addresses - the web site in question is listening on 192.168.1.61, but this issue also happens when it listens on the physical card's address 192.168.1.21

[Peter Godron · Accepted solution]

David,
did you go through this thread ?
http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=109413

[Bill Hassell]

ping your gateway from the HP-UX box. If it fails, your network administrator has turned off internal ping responses from the gateway (a bad idea). Normally, the network admin would turn off ping responses to the outside world but internally, it makes no sense.

For HP-UX ver 11.00 and up, there is a dead gateway detection feature that is on by default. This feature will ping the gateway every few minutes to make sure it is still there. For security, many network admins will disable ping responses for the gateway and HP-UX will disable the route after a few minutes.

To see if the setting is turned on or off, use:

ndd -get /dev/ip ip_ire_gw_probe

1 means the detection feature is enabled. To turn off this feature:

ndd -set /dev/ip ip_ire_gw_probe 0

This is a temporary change. To make it permanent, edit your /etc/rc.config.d/nddconf file to add:

TRANSPORT_NAME[1]=ip
NDD_NAME[1]=ip_ire_gw_probe
NDD_VALUE[1]=0

Be sure to substitute the next available array element for [0] in case [0] is already in use.

Note also that for 11.00, early versions of ndd had a bug that prevented the changes in nddconf from taking effect. Get the latest ndd patch.

[David Connolly]

Bingo!

I noticed (but ignored) dropped ICMP echo traffic from this system on the firewall logs. Thanks for the pointer Peter - sorry I didn't see that thread on my search.

I resolved by adding the following to the /etc/rc.config.d/nddconf file

# don't check the default gateway
TRANSPORT_NAME[10]=ip
NDD_NAME[10]=ip_ire_gw_probe
NDD_VALUE[10]=0

[David Connolly]

Thanks folks - Bill I saw your reply after posting mine :)