HP-UX Routing tables

[Adrian Killops_3]

Hi,

Occasionally a network address appears in the routing table when I do a netstat -r . This address is invalid, and I need to know what can add an entry to the routing table, or how I could prevent a particular ip address from being written? Any suggestions welcome, i am not a Unix guru, so if possible keep it simple!! Thankyou.

[Duncan Edmonstone]

Adrian,

Couple of options:

1. Do the addresses that get added have a 'D' flag associated with them in the Flags column?

If so these are caused by ICMP redirects from routers on your network. The routers are telling the system a more efficient way of reaching a destination. I don't think you can tell HPUX to ignore ICMP redirects (there's nothing in the supported or unsupported IP tunables listed by doing ndd -h supported or ndd -h unsupported).

2. Is gated running? If so then this system may be acting as a router itself and actively listening to router traffic from protocols such as RIP or OSPF etc.


HTH

Duncan

[W.C. Epperson]

In what way is the adddress invalid? It might help if you post a sample line from netstat -r.

[Ron Kinner]

It would help if you gave us your OS version. I wonder if you are running 11.0 and that the reason the new addresses are "invalid" is that they don't respond to a ping. HPUX 11.0 by default will refuse to even try to use a gateway which does not respond to a ping. You can turn this stupid feature off in ndd

ndd -set /dev/ip ip_ire_gw_probe 0

and also edit /etc/rc.config.d/nddconf to add:

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

(use the next higher integer in the brackets if you already have something there.)

Ron

[V.Tamilvanan]

Hi,
My one cent addition to Ronne's contribution.
We need to remove and readd the route to take effect immediately without rebooting .

# ndd -set /dev/ip ip_ire_gw_probe 0
# route delete destination [netmask mask] gateway
# route add destination [netmask mask] gateway [metric]

HTH

[Keith Bevan_1]

Adrian,

Another source for spurious routes visible via netstat -r, is when someone attempts to ping or trace a route that is unreachable. This may on occassions add an entry to the host routing tables.

Keith