eth1 routes to eth2, but no the opposite

[fdelval]

Hello, check the ttached file.


I have a host in 192.168.3.x and another in 192.168.4.x

Both conect to same server with 2 interfaces ending in .254


I have no iptables rules, i activated /proc/sys/net/ipv4/ipv4_forwarding to 1


The host 192.168.3.3 can ping 192.168.3.254 but not 192.168.4.254
The host 192.168.4.4 can ping 192.168.3.254 and can ping 192.168.4.254


Why?

[markcole]

You need to add a route for the .4 subnet so that the .3 knows where to go.

[fdelval]

You need to add a route for the .4 subnet so that the .3 knows where to go.

this are the default routes when this problem is taking place:


192.168.4.0........0.0.0.0...........255.255.255.0 .... u .... 0 ..... 0 .... eth1
192.168.3.0........0.0.0.0...........255.255.255.0 .... u .... 0 ..... 0 .... eth0
0.0.0.0 ........ 192.168.3.1...........0.0.0.0.... ug .... 0 ..... 0 .... eth0



i didnt add a route for the .3, so why does it happen?

[markcole]

this are the default routes when this problem is taking place:


192.168.4.0........0.0.0.0...........255.255.255.0 .... u .... 0 ..... 0 .... eth1
192.168.3.0........0.0.0.0...........255.255.255.0 .... u .... 0 ..... 0 .... eth0
0.0.0.0 ........ 192.168.3.1...........0.0.0.0.... ug .... 0 ..... 0 .... eth0



i didnt add a route for the .3, so why does it happen?

The system set 3.1 as the default route for whatever reason. The reason you cannot ping the .4 network from the .3 network is because it doesn't know where to send it, so I tries the default route, which is wrong for the .4.

You need to add a route for the 192.168.4.0 and tell it to go to 192.168.4.1 (eth1).

[fdelval]

The system set 3.1 as the default route for whatever reason. The reason you cannot ping the .4 network from the .3 network is because it doesn't know where to send it, so I tries the default route, which is wrong for the .4.

You need to add a route for the 192.168.4.0 and tell it to go to 192.168.4.1 (eth1).

mmm i dont know; i deleted the default route, rebooted the server, checked that no route default gw is present, and still, the stange problem persists

[markcole]

What happened when you added the route for the .4 network?

What does a "route -n" give you?

[Lazydog]

STOP!!!!!!

There is no need to add/remove any routes they are all there.

192.168.4.0........0.0.0.0...........255.255.255.0 .... u .... 0 ..... 0 .... eth1
192.168.3.0........0.0.0.0...........255.255.255.0 .... u .... 0 ..... 0 .... eth0
0.0.0.0 ........ 192.168.3.1...........0.0.0.0.... ug .... 0 ..... 0 .... eth0

The mask tells us that the network is for a class C.
The first route is to inform the system that anything going to .4.* is to use eth1
The second route is to inform the system that anything going to .3.* is to use eth0
The last route says anything else is to go out eth0.

Since .4 is known as we can see from the first route the pings should be going out eth1 but there are not.
Next thought is maybe the firewall.

What does the firewall look like? Is it blocking?

[markcole]

STOP!!!!!!

There is no need to add/remove any routes they are all there.

The mask tells us that the network is for a class C.
The first route is to inform the system that anything going to .4.* is to use eth1
The second route is to inform the system that anything going to .3.* is to use eth0
The last route says anything else is to go out eth0.

Since .4 is known as we can see from the first route the pings should be going out eth1 but there are not.
Next thought is maybe the firewall.

What does the firewall look like? Is it blocking?

Good catch. For some reason I read it as eth0.