topic Re: About default route in Operating System - HP-UX

About default route

Wendy_9 — Sat, 09 Mar 2002 09:05:32 GMT

I have a problem regarding to default route. The case is that

The default route is not working if the default gateway cannot be ping. (As set in the firewall, the gateway cannot be ping by any machine and cannot change it). The thing that I want is when default route is used, cannot go
to ping the default gateway and just go out through the default gateway without ping it. Could you please give me a hand for this? As told by somebody, there are some parameters to set in HP 9000 server in order to solve the problem but do not know what parameter is.

Re: About default route

Steven Sim Kok Leong — Sat, 09 Mar 2002 09:09:34 GMT

Hi,

Disable dead gateway detection by executing:

# ndd -set /dev/ip ip_ire_gw_probe 0

To permanently set it in your system startup, modify your /etc/rc.config.d/nddconf:

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

Note that the index must be unique if you already have other values set inside the configuration file.

Hope this helps. Regards.

Steven Sim Kok Leong

Re: About default route

Wendy_9 — Tue, 12 Mar 2002 16:14:33 GMT

I cannot find ip_ire_gw_probe in the machine but have found ip_ire_gw_probe_interval instead. When I try to set this parameter to 0, the system responses "operation failed, invalid argument". Therefore, I cannot set anything at all.

Re: About default route

Craig Rants — Tue, 12 Mar 2002 16:18:55 GMT

This only applies to a 11.x box and you may need some patches.

Here is my notes on the subject.

???HPUX 11.00 supports multiple gateways using route add. It will use default first and check to see if the default router is available by sending it a ping. If it doesn't get a reply, it will consider the route dead and move to the next gateway defined. If there are no other gateways defined then it will shut down all outbound traffic. The fix is to make sure that your router responds to ICMP requests or to run this command to turn probing off 'ndd -set /dev/ip ip_ire_gw_probe 0'
then add an entry in /etc/rc.conf.d/nddconf to turn the probing off at each reboot. Then re-add the route and everything works???

- It was discovered that 10.15.248.1 would not accept ICMP traffic, thus it was considered a ???Dead Gateway??? and all traffic would be routed through 10.15.248.5. I tried to change this parameter, but ip_ire_gw_probe was not an option, so my search continued. I finally found this post on at http://aa11.cjb.net/hpux_admin/2000/04/0209.html

???I finally gave up and called HP support on this. Two sentences into my
description, he knew what the problem was. He also told me "You would have
never found it"

The problem was a little feature in HPUX 11.0 know as 'Dead Gateway
Detection'

What happens is, HP pings the router occasionally (180000 seconds is the
default) to make sure it is still up. If it doesn't get a response, it
stops routing to that address. Since we are using a firewall as a the
default gateway, and the firewall doesn't respond to pings (stealth mode),
then HP assumes the gateway is down and stops routing to it. This also
explains why it wasn't a problem when I had the system on our other network,
that uses a router instead of the firewall.

The fix it to load patches PHNE_20735 and PHNE_20316 and then put the
following entry into /etc/rc.config.d/nddconf

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

To check the current value, use:

ndd -get /dev/ip ip_ire_gw_probe

You can also set the value by using:

ndd -set /dev/ip ip_ire_gw_probe 0

although you will have to reset it after reboot (so just go ahead and set it
up in nddconf)???

GL,
C

Re: About default route

Patrick Wallek — Tue, 12 Mar 2002 16:22:38 GMT

What version of the OS are you on?

I have tried the following command on both 11.0 and 11i and it works:

# ndd -get /dev/ip ip_ire_gw_probe
1

I also did the following on my 11i box:

# ndd -set /dev/ip ip_ire_gw_probe 0
#ndd -get /dev/ip ip_ire_gw_probe
0

Note that there is a space between /dev/ip and ip_ire_gw_probe

Re: About default route

Wendy_9 — Tue, 12 Mar 2002 16:35:24 GMT

The OS is 11.0 and cannot find ip_ire_gw_probe. Can I need to upload such patches in order to use this feature

Re: About default route

Craig Rants — Tue, 12 Mar 2002 16:48:28 GMT

Get the patch or have your network guy allow icmp traffic from your hp server.

C

Re: About default route

Wendy_9 — Tue, 12 Mar 2002 16:58:48 GMT

Allow icmp traffic is meant that the default gateway can be allowed to ping by HP server. Or something set at HP server to achieve this

Re: About default route

Ron Kinner — Wed, 13 Mar 2002 02:35:38 GMT

Your other alternative is to try to use proxy arp. Set the default gateway to point to your own interface. This causes the HP to arp for all addresses. On most routers proxy arp is on by default so the router will reply with its own MAC. It's a tad slower than a default route so it's not used much but if all else fails give it a shot.

Ron