Cannot ping B from A until B pings A

Question

I have a server cluster all connected on a local network(all physical machines, not virtual). When trying to ping from Server A to B, I get a Desitination Host Unreachable. I can ping from B to A no problem, which then allows me to ping from A to B for a short while. Because of this behavior I believe I have an ARP issue, although I do not know how to fix it. When running arp -a I get the following result ? (10.0.0.105) at <incomplete> on eth1, which is the IP I am trying to ping. Not sure if it will help at all but here is my /etc/network/interfaces files for the both machines(I am running Ubuntu 12.04 Server).

Server A
auto eth1
iface eth1 inet static
        address 10.0.0.102
        netmask 255.255.255.0

Server B
auto eth1
iface eth1 inet static
        address 10.0.0.105
        netmask 255.255.255.0

Every other server(I have 7 in this network) can be pinged / can ping any other server. It is just a problem between these two. Any help would be greatly appreciated.

Edit

Server A
iptables --list 

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

Server B
iptables --list

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

How is your iptables configured on both? – Nathan C Jul 09 '13 at 14:24 — Nathan C, Jul 09 '13 at 14:24
Updated with iptables for both. – Eumcoz Jul 09 '13 at 14:30 — Eumcoz, Jul 09 '13 at 14:30

Sirch · Accepted Answer · 2013-07-09T14:52:33.093

6

Does sound like a arp problem, if its long spanned vlan over a vpn or similar, you may need to add static arp entries, with an ether address of the local switch.

arp -s <destination address> <mac address> -i <interface to go out via>

And if thats the fix, you will have to add this to command to start up scripts.

edited Jul 09 '13 at 14:52

answered Jul 09 '13 at 14:36

Sirch

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Is ether the mac address or ethernet port? And which machine do I add this too? Server A(10.0.0.102), or Server B(10.0.0.105)? I would've thought I would have to do `arp -s 10.0.0.105` from on the 10.0.0.102 since I cannot ping from that machine. – Eumcoz Jul 09 '13 at 14:42
1

Add it to the server that cant ping, ether address is the mac address. If these two servers are on the same local broadcast lan, then this isnt the solution, could you descript your network? – Sirch Jul 09 '13 at 14:48
This worked, the command I used was `arp -s -i eth1` for any future people that have this problem. Thank you for the help. – Eumcoz Jul 09 '13 at 14:49
Ah sorry, my solution was for solaris, ill add the -i to answer for ubuntu – Sirch Jul 09 '13 at 14:51
Oh and I am not 100% sure how the servers are hooked up, I dedicated boxes at a data center. – Eumcoz Jul 09 '13 at 14:52
2

you might want to raise a support call with your kind network people, you shouldnt have to add this, the switches might prefer to do the arp proxying, but tell them what you did to fix it and theyll understand what to do. – Sirch Jul 09 '13 at 14:54
Will do, just wanted a quick fix and to make sure it wasn't something on my end. Thank you again. – Eumcoz Jul 09 '13 at 15:00

Cannot ping B from A until B pings A

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