meru reporting restricted ip addresses being issued

jjohnsoncantell · May 14, 2014

Greetings,

When browsing through the station list on my meru controller I'm disturbed to see IP addresses that are excluded from distribution being allocated. We've had a lot of problems lately with networking whereby student phones seem to be taking addresses which are statically assigned to to servers. In my dhcp address pool I have those addresses specifially excluded from use so i cant understand why they are being reported as used.

Im not sure where the fault lies, im posting about it here because its only on the meru controller that ive noticed this problem.

Any advice would be welcome.

James

jjohnsoncantell · June 9, 2014

Hi all,

Still getting this problem, does anyone have an idea what may be causing this?

Thanks

James

fredbayker · June 10, 2014

Is your DC not also your DHCP server?

what does DHCP server report?

jjohnsoncantell · June 10, 2014

Yes its our dhcp server. Its not showing those addresses being leased because theyre excluded from distribution. The meru controller however does show theyre being issued. I had the same problem today, my nas storage was playing up, i did an arp /a to show what mac was assigned to that address and it showed the nas box. I shut down the nas box, cleared the arp cache and after 5 mins checked again, lo and behold a different mac address which turned out to be a students phone on the wireless. Something is definitely not right.

jjohnsoncantell · June 10, 2014

When this has happened in the past, ive checked to see if the offending devices had static addresses, they did not. They were on dhcp.

clareq · June 10, 2014

Have you a rogue DHCP server anywhere? We had a member of staff plug in a home broadband router for some reason once, and saw a similar issue.

jjohnsoncantell · June 10, 2014

Interesting thought, how would i go about finding out? Although, if was something from home use i expect it would be a different gateway and subnet being assigned. Ive got noone complaining about network access problems so far.

clareq · June 10, 2014

I can't remember how we tracked it down, I'm afraid.

psydii · June 10, 2014

Stick Wireshark on a port and mirror the traffic coming from the Meru controller to the DHCP server (filter for DHCP traffic)

When you hit a conflict take a look in the traffic capture - at the very least you should be able to confirm whether your DHCP server issued the IP. If it didn't then you need to take a look at your Wireless Controller, as it can also act as a DHCP server.

Edited June 10, 2014 by psydii

jjohnsoncantell · June 11, 2014

Thanks for your replies guys. Ive had a check at the meru controller setup, one option confuses me a little. Here is the blurb from the manual regarding dhcp passthrough. Currently we have this option turned on, from what is said below please can you confirm whether that is correct as im thinking it should be off.

In the DHCP Relay Passthrough, select one of the following:
- On: Enables the DHCP Passthrough; the default setting where DHCP packets are passed through the controller unchanged. With this option, you must configure DHCP relay on any routers between the 802.11 clients and the DHCP server. With this setting, the DHCP Server IP address field in Step 6. is ignored.
- Off: Disables the DHCP Passthrough. With this setting, DHCP relay

psydii · June 11, 2014

Our core switch does the routing between subnets/VLANs and has the DHCP relay configured.

Our Meru has DHCP Relay pass through set to 'On'.

fredbayker · June 11, 2014

I haven't used any meru kit before but it seems like you've got the correct settings for DHCP pass through.

you need to dig deeper, get wireshark on like psydii suggested. you may just have a rogue DHCP server somewhere.

have you checked the switches for any DHCP config?

jjohnsoncantell · July 2, 2014

there arent any odd settings on the switches.. Gonna try wireshark and see what happens. Thanks guys

jjohnsoncantell · July 4, 2014

ive run wireshark today and the only server i can see responding to dhcp requests is my main dhcp server. I did however notice something odd.

I started a ping log to a client which reported a duplicate address again this morning (log attached), since id switched it off to make sure it wasnt responding to the ping request i was getting the usual "destination host unreachable" by the ip address of my computer. However. every so often, the ping request timed out and my meru controller responded with "destination host unreachable" instead before it went back to normal. If im correct this should not be happening.

Pinging 192.168.0.14 with 32 bytes of data:

Reply from 192.168.3.79: Destination host unreachable.

Request timed out.

Reply from 192.168.0.10: Destination host unreachable.

Reply from 192.168.3.79: Destination host unreachable.

Request timed out.

Reply from 192.168.0.10: Destination host unreachable.

Reply from 192.168.3.79: Destination host unreachable.

psydii · July 5, 2014

What happens when you run continuous ping to host which is actually on? Maybe you are seeing genuine packet loss?

jjohnsoncantell · July 7, 2014

I just ran a continuous ping with the server running and no packet loss reported after 20 mins.

psydii · July 7, 2014

I just ran a continuous ping with the server running and no packet loss reported after 20 mins.

Report it to Meru, ask for an explanation of the observed behaviour.

jjohnsoncantell · July 7, 2014

yeah that was my next port of call, just checking really to see if anyone else has experienced this sort of behavior before i sit waiting for a phone call lol

jjohnsoncantell · July 7, 2014

They couldnt really explain it, rather frustrating. Problem is i couldnt reproduce the issue, i had it happen loads of times last week too. Back to the drawing board

psydii · July 7, 2014

Hmm. Keep the ticket open and update them as soon as you see it happening again.

psydii · July 7, 2014

Hmm. Keep the ticket open and update them as soon as you see it happening again.

meru reporting restricted ip addresses being issued

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