cisco linktest question

[Alexey Kurchenko]

hi all.

I have a question whether I understand correctly that when using the linktest command on the controller, l2 packets are exchanged between the access point and the client. The IP is not used in this case? Or is it a simple ICMP ping?

Thanks.

[Ric Beeching · Accepted solution]

It is layer 3, the WLC will source the request from the interface of that WLAN or I guess its management interface if the client is connected via FlexConnect. The AP->Client comms is layer 2 but that's like all traffic.

Ric

[Alexey Kurchenko · Accepted solution]

but then it's a ping WLC to the client. And the losses may not be in the radio. I thought only the radiolink was being tested. Like RF-ping.

[Ric Beeching · Accepted solution]

Yep correct, that's the way it is without some sort of client-side support like CCX extensions that can share further information with the AP but the WLC feature is just a simple ICMP tool.

If you were to try and initiate a layer 2 'ping' to a wireless client, what frame would you send that it can respond to in the affirmative without requiring some extra knowledge of how to do so? The AP could monitor for an ACK of any kind potentially I guess...

More food for thought, what if this were 2 L2 clients attached to the same switch. How would one client communicate with another directly and expect a response without there being an application that were monitoring specifically for it. I'm thought rambling a bit here as it has got me thinking a bit about it!

Cheers,

Ric

[Alexey Kurchenko · Accepted solution]

Thanks Ric.

Indeed, as I myself did not guess. Of course, you can't do this without client support. But then I would be satisfied with a ping from the AP radio interface to the client to exclude the wired network segment.

As I understand it in WLC ping goes from the controller interface through the CAPWAP to the AP and then to the client. Is this correct?

[Ric Beeching · Accepted solution]

Yep it has to unless the site is FlexConnect with local switching, in that case the ping will be outside of the CAPWAP tunnel as it is switched at the AP port.

[Alexey Kurchenko · Accepted solution]

Thank You, Ric.