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VOIP phone reset when DHCP lease expires across wireless bri

by kevinkapp / November 6, 2012 12:17 AM PST

A few months ago we installed a new Mitel 5000 HX controller. Throughout I will refer to two locations Building A and Building B.

Building A contains all the network equipment. Switches, routers, server, and phone system. Building A is also where the Internet connection comes in as well as the phone lines from the PSTN. In Building A they have a Mitel 5000 HX controller with 2 LSM-4 loop start module 13 8528 digital phone (non-IP), and and 5340 IP phone.

In Building B they have a total of 5 Mitel IP phones. A 5324, 5312, 5340. (2) 5304 and one computer.

The buildings is connected together with two Engenius EN500 in a AP Client bridge mode. The AP Bridge is about 200 feet apart and has line of site communications. The speed is excellent across the bridge is excellent delivering Internet speed tests any where from 25Mbps to 60Mbps. '

So here is my problem.

The 5 IP phones in Building B reset every time their DHCP lease expires. The IP phone in one IP phone in Building A does not reset. So I'm thinking it has something to do with DHCP running across the wireless bridge. They will reset like clock work every 24 hours which coincides with their DHCP lease. Their DHCP server is a Linksys E300 wireless AP / router / firewall. I am not real comfortable about this being their DHCP server but it is the best solution at this time till they can get a real server.

In Building B they are running off a brand new POE Netgear switch, which we just replaced because their old one overheated and died. This new switch is running very nicely and handling things very good. It also runs very cool.

Here is what we have done to troubleshoot the problem so far. We have swapped out both Engenius access points. They used to run a pair of EOC2611P, which run on 2.4Ghz. We found that they were extremely slow because of all the 2.4Ghz signals in the area. A site survey revealed about 30 other AP in their range. We were having all kinds of problems with the network dropping and it being extremely slow. We put in the ENH500, which are 5Ghz AP's, and it took care of the problem. A site survey revealed only one AP in the area and we placed the wireless bridge on a channel that was more that 40Mhz away from the other AP we found on the site survey.

By the way if anyone needs detailed info on how to setup Engenius AP's in a bridge configuration I have created a cheat sheet that is very simple. You can have it setup in just a few minutes. The manuals from Engenius are horrible and do not give specific examples on how to setup the AP's for different operations. Anyone wishing to have this document just let me know and I will send it to you.

We can pull the phone logs off the Mitel 5000 and see that the extensions in building B go offline and back online within a minute or less. We went on site to see what happens to the phones when they when the errors are generated in the log. Like I said it is like clockwork according to their DHCP lease. Watching the phone screens it says some thing to the effect DHCP lease expired <> resetting and the phone reboot. It happens to all IP phones in Building B. It also coincides with the DHCP renew of a computer over there. The computer handles the DHCP renew just fine.

We set the DHCP server to 4 days instead of every day. I know Linksys AP's are one day by default but 4 days is perfectly fine for them. So now the resets only happen every 4 days.

Here are my ideas for fixing the problem but not sure if it will work. I have been on-site so much I just feel at this time I want to just leave things alone for a while.

1. Change the DHCP server to another device.
2. Change the AP's bridge mode from Client Bridge to WDS Bridge. This I am told mimics a CAT5 Cable going across the two bridges. Maybe the phones are having trouble with how a Client Bridge mode because it works a little different.

I am wondering if anyone has ever run into this problem or similar and what might be a solution.

Kevin Kappenman

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All Answers

Best Answer chosen by kevinkapp

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In short yes.
by R. Proffitt Forum moderator / November 6, 2012 12:21 AM PST

Your support for this should provide fixes. I didn't see you provide manuals (links are fine) so I can't check if you can change the DHCP lease time but my question is a simple one. Why not assign IPs and be done with this?

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Yes I see you point
by kevinkapp / November 6, 2012 12:25 AM PST
In reply to: In short yes.

Static IP's on the phones would solve the problem. I am just really curious why this is happening because we have worked with this phone system for many years and with many customers and I would just like to know what the is going on that is different than any other of our clients. This is the only client we have this issue with and we cannot reproduce it in the office.

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Tipping my hand
by R. Proffitt Forum moderator / November 6, 2012 12:36 AM PST
In reply to: Yes I see you point

I write embedded apps. I've been on teams that use IP in DVRs and more so it's up to us to decide what actions to take when the DHCP renews. It appears the maker's coders have decided to do a drop on DHCP renew. It's perfectly understandable from my perspective. However as I find more of this work going overseas it's often impossible for us to get them to change the code.

So unless you find the code that is running these devices the real why must be kept under wraps.

Hope this clears that up.

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I have heard that
by kevinkapp / November 6, 2012 1:02 AM PST
In reply to: Tipping my hand

I have heard that before. I have also read on the internet about VOIP phone in general that reset when the renew their lease. It is sure strange that we have not seen this problem on this system before. We have been installing these same systems and configurations for years and have not see this. We even use the same VOIP system in our office and do not have this problem.

Thanks for your reply

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Just to recap.
by R. Proffitt Forum moderator / November 6, 2012 1:07 AM PST
In reply to: I have heard that

The systems can have different firmware which can also cause fun things like this. For me it's all fun because I'm in this sort of embedded software works. Sadly as I see more software buried deep like this, and makers that are loathe or unable to discuss their products I find myself offering quick fixes such as above.

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by kevinkapp / November 6, 2012 2:14 AM PST
In reply to: Just to recap.

The quick fixes will probably have to do since you cannot get Vendors of the hardware TS to admit to any problems in their products. Thank you for your help. The Static DHCP thing was kinda in the back of my head but my boss wanted me to find out what was going on. You might just have provided the answer.

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