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I have a few servers in one rack. They all have 2 network interfaces eth0 and eth1. On all, eth0 has a public IP address assigned which works well. I'm setting up a private subnet on the second eth1 interface, but no matter what I do, the servers can't seem to see each other if i ping them on the 192.168.1.* range. Thanks in advance, Harel

Using 2 servers as an example, neither can ping/ssh eachother via the 192 range:

Server 1:

eth1      Link encap:Ethernet  HWaddr 00:26:b9:76:9d:43  
      inet addr:192.168.1.5  Bcast:192.168.1.255  Mask:255.255.255.0
      UP BROADCAST MULTICAST  MTU:1500  Metric:1
      RX packets:0 errors:0 dropped:0 overruns:0 frame:0
      TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
      collisions:0 txqueuelen:1000 
      RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
      Interrupt:17 Memory:dc000000-dc012100 


spiderman:/home/harel# ip route show
X.X.X.X/29 dev eth0  proto kernel  scope link  src X.X.X.X 
192.168.1.0/24 dev eth1  proto kernel  scope link  src 192.168.1.5 
default via X.X.X.X dev eth0 

Server 2:

eth1      Link encap:Ethernet  HWaddr b8:ac:6f:8a:78:fd  
          inet addr:192.168.1.10  Bcast:192.168.1.255  Mask:255.255.255.0
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
          Interrupt:17 Memory:dc000000-dc012100 

hulk:/home/harel# ip route show
X.X.X.X/29 dev eth0  proto kernel  scope link  src X.X.X.X
192.168.1.0/24 dev eth1  proto kernel  scope link  src 192.168.1.10 
default via X.X.X.X dev eth0 

Obiously the public ips above are masked as X.X.X.X

There are no iptables rules defined on any server:

hulk:/home/harel# iptables -L
Chain INPUT (policy ACCEPT)
target     prot opt source               destination         

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination         

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination  
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Are the computers connected to a separate switch or a separate VLAN? –  SvW Jan 27 '11 at 16:26
    
According to the data centre people both ports are connected to a switch. I have no physical access to the machines.... –  Harel Jan 27 '11 at 17:07
    
I have no physical access to the machines or the switch. –  Harel Jan 27 '11 at 17:10
    
Then let the DC staff verify that the ports are configured appropriately. –  SvW Jan 27 '11 at 17:20
    
it's very difficult to troubleshoot something like this without physical access to the hardware. At this point I would have your datacenter staff proceed with Mike Scott's suggestion to verify that the computers can talk to eachother when directly connected. If that works your problem is at the switch ; if not you can concentrate on the servers. –  voretaq7 Jan 27 '11 at 17:43
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4 Answers

up vote 1 down vote accepted

It sounds like your datacenter people are isolating each server/port. Let them know what you want to do :-)

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Maybe that ticket here should have read "Why does DC support staff are never proactive problem solvers"... I let them know what I want, I bought the services that 'enable' what I want, and yet I now need to pay for support to get what I want.... Show me a good DC in the UK that is not rackspace-pricey and i'm in.... –  Harel Jan 27 '11 at 21:38
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Do you control the switch which the eth1 interfaces are connected to? It's possible there could be filtering happening there.

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I have no physical access to the machines nor can i control the switch.... –  Harel Jan 27 '11 at 17:09
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Try connecting the eth1 ports on the two servers directly to each other with a crossover cable, to rule out other problems on the network. If it still doesn't work, you may have faulty hardware somewhere.

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The problem was the wiring to the switch. It has been rewired and now works great. Thanks for all your help guys. Sorry I can't upvote answers - not enough rep on serverfault....

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Rewired huh? I'd take that with a grain of salt. Did your ifconfig how any cable trouble (half-duplex, lower speed, no carrier) ? –  DutchUncle Jan 28 '11 at 20:24
    
Nope. It showed everything is as it sohuld have been, and this is why I came here to ask. Everything looked Kosher... The said they tried a different wiring configuration. I don't care really as long as it works ok now –  Harel Jan 31 '11 at 9:52
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