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ARP issue between only 2 computers on the same LAN (all ~100 others are ok)

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C_Juillac
Occasional Visitor

ARP issue between only 2 computers on the same LAN (all ~100 others are ok)

Hello,

 

First I would like to thanks this community because I've used it to find many solutions since nearly ten years now.

 

Now I'm facing a network issue for wich I can't find any information here (or via googling it).

 

On a LAN of nearly 100 computers, I have 2 computers which suddenly can't contact each other (ping/tcp/udp), but it was working for weeks.

 

The network topology :

 

computer A ---- switch9 (2510-48) ---- router (OmniSwitch 6850) ---- switch10 (2510-48) ---- computer B

 

computer A 192.168.2.101

computer B 192.168.2.140

 

router 192.168.2.254

 

After wiresharking from computer B, I can see that B never ask for A's MAC address, and when A is asking for B's MAC address, B does not respond.

 

A and B can contact all others computer on this network (and on routed networks).

 

show arp on switch10 (after ping on A & B)

IP ARP table

IP Address MAC Address Type Port
--------------- ----------------- ------- ----
192.168.2.22 b8ac6f-1226e1 dynamic 49
192.168.2.100 0026b9-8d77cf dynamic 49
192.168.2.101 0026b9-8e5abf dynamic 49
192.168.2.109 90b11c-a7b2d4 dynamic 49
192.168.2.140 ecf4bb-1df730 dynamic 13
192.168.2.183 002219-162b50 dynamic 49
192.168.2.254 00e0b1-b74c90 dynamic 49

 

show arp on switch9

IP ARP table

IP Address MAC Address Type Port
--------------- ----------------- ------- ----
192.168.2.22 b8ac6f-1226e1 dynamic 49
192.168.2.100 0026b9-8d77cf dynamic 49
192.168.2.101 0026b9-8e5abf dynamic 25
192.168.2.140 ecf4bb-1df730 dynamic
192.168.2.254 00e0b1-b74c90 dynamic 49

 

As you can see, switch9 know B's mac-address but it is not associated with any port on the switch.

 

It seems that switch9 not properly learn B's mac address, but I can ping B from switch9.

I've done a show mac-address on switch9, but B's mac address was not listed (A's one was).

 

Any help would be greatly appreciated.

 

Regards.

1 REPLY
C_Juillac
Occasional Visitor
Solution

Re: ARP issue between only 2 computers on the same LAN (all ~100 others are ok)

I've reloaded switch9, it has solved the problem.