Solved

DHCP Lease times and IP Phones

Posted on 2007-03-29
6
945 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
  • 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 200 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
How to improve team productivity

Quip adds documents, spreadsheets, and tasklists to your Slack experience
- Elevate ideas to Quip docs
- Share Quip docs in Slack
- Get notified of changes to your docs
- Available on iOS/Android/Desktop/Web
- Online/Offline

 
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 300 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

What Should I Do With This Threat Intelligence?

Are you wondering if you actually need threat intelligence? The answer is yes. We explain the basics for creating useful threat intelligence.

Join & Write a Comment

Suggested Solutions

Title # Comments Views Activity
SIP Trunk provider 20 93
Microsoft AD for Secure LDAP 3 39
VOIP grade small switch 4 41
DHCP Failover Relationship caveats 6 55
A common practice in small networks is making file sharing easy which works extremely well when intra-network security is not an issue. In essence, everyone, that is "Everyone", is given access to all of the shared files - often the entire C: drive …
If your business is like most, chances are you still need to maintain a fax infrastructure for your staff. It’s hard to believe that a communication technology that was thriving in the mid-80s could still be an essential part of your team’s modern I…
This video discusses moving either the default database or any database to a new volume.
In this tutorial you'll learn about bandwidth monitoring with flows and packet sniffing with our network monitoring solution PRTG Network Monitor (https://www.paessler.com/prtg). If you're interested in additional methods for monitoring bandwidt…

707 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

Need Help in Real-Time?

Connect with top rated Experts

18 Experts available now in Live!

Get 1:1 Help Now