Strange Routing Tables Destinations !

[Ivan Azuara]

Hi !

I want to know if this is a configuration problem on my HPUX 11i server, or is a problem on my routers.

The problem is the next:

a) "netconf" configuration file:

INTERFACE_NAME[0]=lan0
IP_ADDRESS[0]=130.10.16.1
SUBNET_MASK[0]=255.255.255.0
BROADCAST_ADDRESS[0]=130.10.16.255
INTERFACE_STATE[0]=up
DHCP_ENABLE[0]=0

ROUTE_DESTINATION[0]=default
ROUTE_MASK[0]=""
ROUTE_GATEWAY[0]=130.10.17.241
ROUTE_COUNT[0]=1
ROUTE_ARGS[0]=""

IP_ADDRESS[1]=130.10.17.1
SUBNET_MASK[1]=255.255.255.0
INTERFACE_NAME[1]=lan1
BROADCAST_ADDRESS[1]=130.10.17.255
INTERFACE_STATE[1]=up
DHCP_ENABLE[1]=0

b) "netstat -rn" command:

Routing tables
Destination Gateway Flags Refs Interface Pmtu
127.0.0.1 127.0.0.1 UH 0 lo0 4136
130.10.17.1 130.10.17.1 UH 0 lan1 4136
130.10.16.1 130.10.16.1 UH 0 lan0 4136
130.30.10.30 130.10.17.228 UGH 0 lan1 0
130.10.143.145 130.10.16.242 UGH 0 lan0 0
130.21.10.8 130.10.17.228 UGH 0 lan1 0
130.21.10.60 130.10.17.228 UGH 0 lan1 0
130.21.10.55 130.10.17.228 UGH 0 lan1 0
130.50.10.23 130.10.17.229 UGH 0 lan1 0
130.60.10.3 130.10.17.229 UGH 0 lan1 0
130.60.196.2 130.10.17.229 UGH 0 lan1 0
130.10.170.94 130.10.17.229 UGH 0 lan1 0
130.50.196.9 130.10.17.229 UGH 0 lan1 0
130.10.16.0 130.10.16.1 U 2 lan0 1500
130.10.17.0 130.10.17.1 U 2 lan1 1500
127.0.0.0 127.0.0.1 U 0 lo0 0
default 130.10.17.241 UG 0 lan1 0

c) use of "traceroute" command to any IP Address:

# traceroute 130.10.19.43
traceroute: Warning: Multiple interfaces found; using 130.10.17.1 @ lan1
traceroute to 130.10.19.43 (130.10.19.43), 30 hops max, 40 byte packets
1 p1-izq (130.10.12.240) 0.812 ms gwlan0 (130.10.17.241) 0.915 ms 2.545 ms
2 130.10.19.43 (130.10.19.43) 1.510 ms 0.526 ms 0.494 ms

I don??t understand why appears a lot of routing tables destinations, if i have defined only the default gateway "130.10.17.241".

May be is a problem in the configuration of my default gateway ?.

Somebody have an idea ?

Thank??s in advance !

[Steven E. Protter]

Your gateway for lan0 is not on the same network as lan0

based on your subnet your network is 130.10.16

The statement
ROUTE_GATEWAY[0]=130.10.17.241

Is not on the same network, its on network 130.10.17

I would think the gateway for lan0 should be on the 130.10.16 network.

SEP

[Ron Kinner · Accepted solution]

There does not appear to be anything wrong with your netconf. It appears that for several destinations the 130.10.17.229 is a quicker way to get where you want to go. This gets in your routing table through a process called icmp redirect. See

http://www.firewall.cx/icmp-redirect.php

for more details but essentially every time the default gateway gets a packet whose next hop is on the same LAN as it was received on it sends an ICMP redirect back to the source saying next time go directly to the next hop and don't bother me. This saves the default gateway some time and speeds up the flow a few milliseconds since it eliminates a hop. This new route stays in your table for a time and if not used will eventually disappear until the next time you send a packet there. You may also see that the first time you trace a packet to a new destination it will go through your default gateway and then on to the next hop. Subsequent traces should then go directly to the next hop and not go through the default gateway unless you wait long enough for the redirect route to age out of the table. It can also happen that most everywhere you want to go is via the other gateway in which case you might want to reconfigure and use it for your default gateway.

Steven,

There is nothing wrong with his default route. The numbers in brackets for the routes are in a different series and do not have to correspond to the bracketed numbers for the lan that they will use.

Ron

[Ivan Azuara]

Can I define 2 different gateways in the "netconf" file ?.

In my case the network 130.10.16, will use the gateway 130.10.16.241, and the network 130.10.17., will use the gateway 130.10.17.241, correct ?.

It??s posible that this diference between the lanics, it be the cause of the entries for diferents hosts gateways ?:

130.21.10.60 130.10.17.228 UGH 0 lan1 0
130.21.10.55 130.10.17.228 UGH 0 lan1 0
130.50.10.23 130.10.17.229 UGH 0 lan1 0
130.60.10.3 130.10.17.229 UGH 0 lan1 0


Thank's in advance !

[Jeff Schussele]

Hi Ivan,

Yes you can define 2 or more gateways, but ONLY one default.
The others would be termed static routes to either subnets or hosts.

Rgds,
Jeff