HP-UX 11.31 Default gateway not getting used

[PW HP-UX Support Team]

I have several HP-UX 11.31 systems (All Itanium, both stand-alone and vPars) that have a default route configured, yet the system does not try to route through it for some reason. The only way I can get traffic to flow over that gateway is to configure a static route for the network I want, and point it to the same gateway that my default i set to. Traffic flows after that. Bizarre.

Here is an example of my routing table:

Destination Gateway Flags Refs Interface Pmtu
10.20.0.0 172.23.36.1 UG 0 lan1 1500
172.22.4.0 172.22.36.1 UG 0 lan0 1500
172.22.27.0 172.23.36.1 UG 0 lan1 1500
172.23.2.0 172.23.36.1 UG 0 lan1 1500
172.18.2.0 172.23.36.1 UG 0 lan1 1500
172.19.0.0 172.23.36.1 UG 0 lan1 1500
172.17.0.0 172.21.62.1 UG 0 lan2 1500
172.21.0.0 172.21.62.1 UG 0 lan2 1500
loopback localhost U 0 lo0 32808
default 172.21.62.1 UG 0 lan2 1500

As you can see from the bottom entries, I have 2 networks I need to reach over the default gateway (172.21.0.0 and 172.17.0.0), but without these static routes configured, traffic does not flow.

Now correct me if I'm wrong, but isn't the point of the default gateway to try and route traffic through it if no other rule is present to override it? What am I missing?

[Matti_Kurkela]

Please show the output of "netstat -rnv". The "v" option is important: it shows the masks associated with each route entry.

The mask values are essential when figuring out how your network routing works. The default gateway entry should have mask 0.0.0.0 to match everything.

The outputs of "ifconfig lan0", "ifconfig lan1" and "ifconfig lan2" would be useful too.

At this point, without seeing any other information, my first guess would be that one of your netmasks (either in the routing table or in the network interface configuration) is perhaps set too wide: for example, it might be intended to refer only to 172.19.*.* but it is accidentally set to cover the entire 172.*.*.* segment.

MK

[PW HP-UX Support Team]

Looks good to me.

Dest/Netmask Gateway Flags Refs Interface Pmtu
10.20.0.0/255.255.0.0 172.23.36.1 UG 0 lan1 1500
142.226.0.0/255.255.0.0 172.23.36.1 UG 0 lan1 1500
172.22.4.0/255.255.255.0 172.22.36.1 UG 0 lan0 1500
172.22.27.0/255.255.255.0 172.23.36.1 UG 0 lan1 1500
172.23.2.0/255.255.255.248 172.23.36.1 UG 0 lan1 1500
172.18.2.0/255.255.255.0 172.23.36.1 UG 0 lan1 1500
172.19.0.0/255.255.0.0 172.23.36.1 UG 0 lan1 1500
172.21.0.0/255.255.0.0 172.21.62.1 UG 0 lan2 1500
172.17.0.0/255.255.0.0 172.21.62.1 UG 0 lan2 1500
loopback/255.0.0.0 localhost U 0 lo0 32808
default/* 172.21.62.1 UG 0 lan2 1500

# ifconfig lan0
lan0: flags=1843
inet 172.22.36.21 netmask fffffc00 broadcast 172.22.39.255
# ifconfig lan1
lan1: flags=1843
inet 172.23.36.21 netmask fffffc00 broadcast 172.23.39.255
# ifconfig lan2
lan2: flags=1843
inet 172.21.62.22 netmask ffffff00 broadcast 172.21.62.255

[Duncan Edmonstone]

So a ping to your default gateway from this system works does it?

HTH

Duncan

[PW HP-UX Support Team]

Most of our servers do not have the ability to ping their gateway as this is a security restriction. However, this particular system requires icmp traffic enabled due to Oracle Clusterware requirements.

This is a non-issue however, as we have many systems that have this gateway issue, in two different datacentres, some with ping enabled and some without. All experience the same gateway anomaly.

We also have many 11.11 and 11.31 systems in a different network environment (corporate flat network) which do not have the issue. the default gateway works fine even and the routers actually ROUTE the traffic.

[Duncan Edmonstone]

so what does the raw routing table say?

ndd -get /dev/ip ip_ire_status | grep IRE_GATEWAY

... does it have the gateway marked as dead? I'm wondering if you should diable dead gateway detection:

# ndd -h ip_ire_gw_probe

ip_ire_gw_probe:

Enable dead gateway probes. This option should only be disabled on
networks containing gateways which do not respond to ICMP echo
requests (ping).
[0-1] Default: 1 (probe for dead gateways)


HTH

Duncan

[PW HP-UX Support Team]

# ndd -get /dev/ip ip_ire_status | grep -e IRE_GATEWAY -e flag
IRE rfq stq addr mask src gateway mxfrg rtt ref type flag
e00000049936c688 0000000000000000 0000000000000000 000.000.000.000 00000000 172.021.062.022 172.021.062.001 01500 00000 000 IRE_GATEWAY