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I have four computers that have nonlocal addresses like 150.X.X.X. Now I also get another few computers that should be only accessible through a gateway (it will be computing cluster) and they addresses are 10.0.0.X. I also wanted to include those four older computers to this new cluster, but I want them to be accessible from internet on nonlocal addresses (so I would like to set up them on both 150.X.X.X and 10.0.0.X addresses - I've set up it as interface eth0:0 since I have only one NIC).

Those new computers have their switch and old computers also have their own switch. Both of them are connected to another (third) switch.

The problem is that those old computers see each other (I can ping them), and also new computers see each other, but I can't ping old computer from new computer and vice versa. However pinging on nonlocal adresses works as expected.

I looked into switch configuration and didn't find anything useful.

I have no idea what I missed here. Can somebody help?

All computers have Ubuntu Server 10.04

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2 Answers 2

You need to set up proper routing between your 150.x.x.x and 10.0.0.x networks. Using a switch (at OSI layer 2) to interconnect the networks won't work (as you have discovered), because, by default, the hosts on your various networks don't know how to route packets (of OSI layer 3) to the other networks.

Basically, you need to interconnect your networks with one or more routers. With everything properly configured, each host will send packets bound for non-local networks to its respective gateway router, and that router will forward those packets on towards their destinations.

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But I don't want to route between 150.X.X.X and 10.0.0.X. On both new and old computers I have set up 10.0.0.X addresses and they are connected with three switches without any router in between, so I just thought it should work, but it doesn't. –  klew Jan 30 '11 at 19:03
    
@klew: Sorry, I misunderstood your question. If all your hosts are on the 10.0.0.x network, and all are interconnected by switches, then you're right, they should all be able to ping each other. You may have some kind of problem with one or more of your switches. Or perhaps the networking config on your hosts is incorrect. Sorry, I cannot offer you anything more than conjecture. –  Steven Monday Jan 30 '11 at 20:22
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Ok, I've found what I did wrong. I didn't know that other person seperated local and nonlocal NICs on new computers by creating VLAN on their's switch. That's why it didn't work as I thought it should.

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