?
Solved

DHCP Lease times and IP Phones

Posted on 2007-03-29
6
Medium Priority
?
969 Views
Last Modified: 2013-12-23
We currently have a relatively small network, 20 servers, 2 DC's. 1 DC is handing out DHCP. We are implementing IP phones. Since we do not have 2 data drops at each location the Workstation will be plugging in to the phones, and the phones plugging in to the network.

So the problem is phones need DHCP and workstations need DHCP. Once the phone attains a DHCP address from our DC it is then flagged as VLAN traffic and gets routed to the IP phone server at which point it gets a DHCP assigned address on a different network. So essentially phones need an address on our network when they first boot up, but then they are transferred to a secondary network.

I wanted to figure a way of handling this without running out of DHCP addresses if the power goes out. Basically i didnt want to have 230 devices looking for an address when only 200 are available in the DHCP scope.

That being said. I could set my lease time very low in the DHCP scope, but I am not sure what the consequences of that would be. Say a lease time of like 5 minutes. I am really wondering how much that will slow down our LAN.

Any recomendations?
0
Comment
Question by:Atomic75
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
  • 2
  • 2
6 Comments
 
LVL 22

Expert Comment

by:WMIF
ID: 18820334
what kind of equipment are you running?  brands, models, etc.  i have my users pcs plugged into our phones and have the switches with different vlans for the networks.  when my phones boot, the switch directs the voice traffic to the voice vlan, and when the pc comes up, it goes on the data lan.  the phones never get an address on the data lan.

i am running cisco equipment.  call manager, 3560 switches, 7961 phones.
0
 

Author Comment

by:Atomic75
ID: 18820348
It is shoretel equipment, with Extreme 24 Port switches. We do not currently have the phones installed. I am just going through the planing stages right now. The technician who installed the switches is the one who told me the only way to do it was to have the phones get an address from existing network so the traffic could then be tagged as VLAN and get routed to the correct location.

Perhaps this is due to the way their equipment runs.
0
 
LVL 22

Assisted Solution

by:WMIF
WMIF earned 800 total points
ID: 18820383
maybe someone else can jump in here with shoretel experience.  that doesnt make sense to me why it would have to jump onto the other network in order to get tagged with a different vlan.  

can you setup a test lab to see if what he says is true?  i have become very cautious about what consultants have told me.  many times they tell me completely wrong.
0
VIDEO: THE CONCERTO CLOUD FOR HEALTHCARE

Modern healthcare requires a modern cloud. View this brief video to understand how the Concerto Cloud for Healthcare can help your organization.

 
LVL 3

Expert Comment

by:KiyamKadir
ID: 18831339
Dear,
basically i would recommend you using a 2 hours lease time if your users are 20% of the time at the same location and 80% of the time roaming.

for the reverse i do recommend you 1 day but not longer.


DHCP Traffic is very low in terms of bandwidth but you should be careful of your server's OS and performance as we have faced many issues with MS Win 2k3 Enterprise where as the DHCP service gets hit when we receive more than 180 simultaneous requests for address renewal.

Also watch out for the performance of your IP PBX server because they have to register the new ip addresses and the mac and directory number association again.

i recommended 2 hours because i have 500 users roaming all time and there is no problem so far.

We are purely running Cisco and Juniper gear.

i hope that it helped and you will have success.

0
 
LVL 3

Accepted Solution

by:
KiyamKadir earned 1200 total points
ID: 18831349
if you are running cisco use the IP HELPER-ADDRESS command to convert all your BROADCAST style DHCP REQUESTS into UNICAST style requests to decrease bandwidth consumption on your network.

Also for FIXED users use 4 days of lease time and prevent using NO LIMITED LEASE time since they cause DB inconsistencies if the DHCP service might crash.

0
 

Author Comment

by:Atomic75
ID: 18837789
Thanks for the help everyone
0

Featured Post

Simple, centralized multimedia control

Watch and learn to see how ATEN provided an easy and effective way for three jointly-owned pubs to control the 60 televisions located across their three venues utilizing the ATEN Control System, Modular Matrix Switch and HDBaseT extenders.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Hey there Heard about jingle, the add on for XMPP that enables point to point audio between two XMPP clients. No server config necessary. Actually quite a cool feature. However, how good is it if you can not use those voice capabilities to do a P…
Why do some people recommend buying business VoIP from an ISP? What are the benefits to my company? What are the costs?
Michael from AdRem Software explains how to view the most utilized and worst performing nodes in your network, by accessing the Top Charts view in NetCrunch network monitor (https://www.adremsoft.com/). Top Charts is a view in which you can set seve…
In this brief tutorial Pawel from AdRem Software explains how you can quickly find out which services are running on your network, or what are the IP addresses of servers responsible for each service. Software used is freeware NetCrunch Tools (https…

764 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question