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Simple Network, unexplained ICMP Timeouts...


I have posted this problem on this forum sometime back but didn't get to the bottom of it so i thought i try one more time as the problem has been put on hold but now needs to be resolved very quickly.

Out client has two sites with a link inbetween. At the remote site they have a 3750 installed with two vlans one production with users pc's, printers a small workgroup server etc the other vlan is commercial for devices to collect data. At the other site or near site there is just a generic L2 switch nothing more. The link between the sites is of low bandwidth and comprises for part of it a simple radio link. The problem is this, if a pc was connected to the switches of both sites and pinged each other there is no problem At the remote site everything can ping each other and both the vlan interfaces of the switch. Now, when the switch pings the nearest wireless access point to itself along the link between the two sites this comes back fine. If it pings the furthest AP (Over the Radio Link) it drops out. As i mentioned previously the PC's connected to both the switches at either end of the link can ping no problem which  then leads us to the switch even though the pc's / servers /anything behind the switch dont have a problem. We have done packet captures and it seems packets are transversing the wireless link and an icmp reply is given by the remote kit but something happens to the packet along the way.  Just to confuse things more the arp table has the entry for the unreachable device that it cannot ping. It would be as if the packet is timing out on transit although the pc / servers / printers are not. There is no acl's the svi's are up on the switch and have no issue from the nearest ap on the link pinging the svi or anything connected to it .

Has anybody come across anything like this before whereas timeout affecting the switch but not pc's behind it. Would there be any timers that can be adjusted on the interface. I have done a extended ping but still no joy.

Hope this is clear, We are just getting absolutely nowhere has anybody got any idea's?


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Re: Simple Network, unexplained ICMP Timeouts...

Hi Mark,

With overview what i understand is end to end connectivity is fine PC's from both sites are able to ping each other but when switch at one site wants to ping the AP of the other sites it getting RTO,If yes Just clarify few things

Switch and the local AP are in different subnet or in same subnet and what happen when you traceroute the far end ap ip address from switch.


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