AP in sniffer mode

[MartinSerupBlakSorensen67875]

Hi, i have a site where we would like to conduct some wireless sniffing but are having some issues since the problem we suspect is AP->Controller traffic.

It seems that we are losing some packets in the CAPWAP tunnel so an AP in sniffer mode on the same controller may not give the full picture.

Can a 2802I running Mobility Express software support a couple of 2702I (or maybe 2802I) AP's running in sniffer mode?

We would like to make sure that all the traffic stay onsite so this is the best solution we could come up with, as an alternative we can maybe setup a WLC onsite where the sniffer AP's can join but this would require alot more work and planning since we don't have a controller available.

Any thoughts or tips would be appreciated.

Kind regards.

Martin.

[Rasika Nayanajith]

Hi Martin,

You do not require to have local controller in branch site to have sniffer mode AP. Even WLC at a central location, as long as Sniffer mode AP can register to that (only require L3 IP reachability between WLC & AP), you are good.

My suggestion is to convert 3702 to sniffer mode and send it to branch (with appropriate CH number set to scan & set wireshark running PC IP set, it can be a device on your central site). Please follow the below post on how to set it up

https://mrncciew.com/2018/04/07/wifi-captures-with-sniffer-mode-ap/ 

HTH

Rasika

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[MartinSerupBlakSorensen67875]

Hi Rasika,

The problem i'm facing is that there may be packet loss on in the CAPWAP tunnel the current controller, so to make sure that i don't also miss alot of the captured packets i would like to have the sniffing handled locally.

The reason being that we see alot of EAP timeouts and we can't really tell if the EAP packets are going missing in the air or in the CAPWAP tunnel or if the client never even send them to start with.

Or does the sniffer traffic not need to go through the WLC?

Hope this makes sense as to why we would like to handle the sniffing onsite.

[Rich R]

Does the CAPWAP transit a Cisco router?

If so then run the pcap on that: https://www.cisco.com/c/en/us/support/docs/ios-nx-os-software/ios-embedded-packet-capture/116045-productconfig-epc-00.html

That's what we do.  Then export the pcap to router flash or directly to tftp/ftp server etc.