Default routes stop working

[Richard Berg]

We have experienced a new problem on HPUX 11.x where our default routes stop working after a couple of minutes if at all. Static routes work fine. The default route remains viewable using netstat -rn but they don't work.

[Berlene Herren · Accepted solution]

Check for dead gateway detection. By default this is one at 11.0. If your firewall is the gateway and doesn't accept ICMP, then after so many tries of pinging, 11.0 will "turn off" the gateway. To see all gateways you could use ip_ire_status

ndd -get /dev/ip ip_ire_status | grep -e IRE_GATEWAY -e flag
This results in a list of all gateways, the flags will indicate a dead gateway.

Another option ip_ire_gw_probe_interval is available which changes the frequency in which such probes will be performed.



Why would this be used?
The gateway probes are ICMP packets which await a proper reply.
In cases where e.g. a firewall is used it could be wanted to turn off ICMP, so nobody could ping the firewall but still it works for the desired protocols.
So turning it off would not compromise the work, because we would never send an ICMP packet to test the machine.
On the other hand we would only know if a gateway is not operational if we try to use it. This results in long timeouts during the detection.



Usable commands:
Check the current value:
ndd -get /dev/ip ip_ire_gw_probe
Disable Dead Gateway Detection:

ndd -set /dev/ip ip_ire_gw_probe 0

Regards,
Berlene

[rajsri]

Hi
If your default gateway is not working ! check the following

1.Can you ping to default route ?

2.what netstat -rn shows for defaultgateway does it say UG on flag

3.Normally packets will be transfered through nearest path first and then next nearest , and finally if doesn't find any route it goes through default route .

[Steven Sim Kok Leong]

Hi,

Check if the arp entry for the host at your gateway is correct.
If it is wrong, you may which to flush that entry via arp -d.

Regards.

Steven Sim.