Let says I have two VLANs, 10.0.1.x and 192.168.1.x. These 2 VLANs have inter VLAN routing enabled.

Computer A: connected to 192.168.1.x with IP

Computer B: connected to both. and

When I ping from A, it is okay. But if I ping, it fails.

However, if I turn off the interface on computer B, then I can reach from A.

Why is that so? What can I do to solve the situation? Any routing table issue involved?

2 Answers 2


That's perfectly normal.

When you ping you emit a ICMP echo request packet with source address and destination address of, and expect a response with source address / destination address

When the computer B responds, it sends a response to Since it has an interface in the same network, with it's IP, it sends the response trough this interface, so the ICMP echo reply message is sent with source address / destination address

Computer A does receive the response but it's not the expected source address, so it does not associate it with the initial echo request.

Now if you turn off the interface, the response is sent trough the other interface with the correct IP address.

Concerning how to solve the situation, it all depends on why you do have computer B multi-homed (I.E. connected to several networks). It's better in most case to avoid this kind of setup.

One way to do it would be to NAT the 10.0.1.X address to 192.168.1.x address for example.


You may be hit by Reverse Path Filtering. Basically Computer B is dropping the incoming ICMP-packets since it wasn't expecting IP packets from on the interface.

It is expecting traffic from the subnet from the interface.

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