DHCP per subnet quandary

[Pigsfoot]

Hi,

We have an Avaya IP phone system running on the same network as a Windows 2008 AD. Due to running out of IP addresses we are looking to move the Avaya system onto a different Subnet but still be able to comminicate with the main Windows subnet..

What i'm not sure about is if we keep the Windows DHCP server running on the primary subnet will it oonly allocate IP addresses to that Subnet. We then want to enable the DHCP server on the phone system so we can issue IP addresses the the Avava handsets on it's own subnet.

I guess what i am asking for confirmation on is to make sure each DHCP servers will not issue IP addresses to the wrong subnet.

If anyone can confirm this it would be much appreciated.

Many Thanks

 

[montyzummer]

you can just tick send ipaddress to avaya ip phones only on the advanced dhcp settings on the ipo but if they are on different subnets never the twin will meet.

APSS (SME)
ACSS (SME)

 

[Pigsfoot]

Thats great, thanks for confirming that. Allways better to hear it from someone else for peace of mind.

Cheers

 

[Pigsfoot]

Sorry, this just popped into my mind.

How will the phones know which server to obtain the DHCP address from when they boot up? i.e. whats to stop them getting an IP address from the Windows server rather than the Avaya.

We have two server rooms connected by Fibre. Each Server room has a bank of 5 x 24 port Netgear switches all stacked together. All our servers and phone system is on one of the server rooms plugged into the stacked switches and we do not use Vlans anywhere.

Thanks

 

[tlpeter]

When you have so much devices on a lan then i suggest you start using VLAN's
Be sure that the DHCP server is on both VLAN's and make another scope for the IP phones.
Make an option 242 in the data scope with only the VLAN settings and make a scope in the voice VLAN with option 242 with the current value's

BAZINGA!

I'm not insane, my mother had me tested!

 

[Pigsfoot]

Thanks for the reply, not really what i wanted to hear but kind of knew it was the answer.

Is there anyway around acheiving what we want to do without Vlans. Reason why we have always tried to avoid them is due to people patching in ports not aware of the Vlan's on the switches and then wondering why it doesn't work. I know it should be better controlled but in our case it's not and trying to re-teach people now is almost impossible.

The original idea of using Subnetting was so we didn't have to use Vlans's knowing two subnets will work and with two DHCP servers, what i need to find a way around is when a handset is booted up it gets a DHCP address from the AVAYA phone system and not the Windows server.

I'm not aware of a way of doing this but can the Windows server forward all DHCP requests from a AVAYA handset to the Avaya phone system but still issues addresses to Windows based clients ?

Thanks in advance

 

[tlpeter]

You build a second scope with option 242 and not adding this in to the first scope.
See what happens
You then need ip routing on layer 3 level i guess.


BAZINGA!

I'm not insane, my mother had me tested!

 

[montyzummer]

unless i misunderstand you could simply put the lan port of the ipo on one subnet with dhcp off and then use lan2(WAN) on the other subnet with the option ticked i described and you will be ok.

APSS (SME)
ACSS (SME)

 

[mattKnight]

Reason why we have always tried to avoid them is due to people patching in ports not aware of the Vlan's on the switches and then wondering why it doesn't work. I know it should be better controlled but in our case it's not and trying to re-teach people now is almost impossible.

If you build your VLANS correctly, this is not an issue.

You data vlan is for untagged traffice and the voice vlan is for tagged traffic.

If you insist on using a nasty approach - which really depends on which DHCP server replies first..., rather than using the correct VLAN configuration, why not just widen the subnet and increase the DHCP pool size and continue to run a a flat network?

Take Care

Matt
I have always wished that my computer would be as easy to use as my telephone.
My wish has come true. I no longer know how to use my telephone.

 

[dialtonebone]

I'm not sure why no one has suggested yet:

Split the system into multiple VLAN's, put the ports into VoIP/Dual Mode so they start on the data VLAN (for PCs and network equipment) but also accept tagged packets. Then tell your Data VLAN DHCP server to tell IP phones via 242/176 that they need to switch VLAN XX (being the Voice VLAN).

After the phone switches to the other VLAN during the boot process, it will then need DHCP again from the voice DHCP server. Create a scope on your DHCP server for the voice equipment, on your router or switches apply a DHCP/UDP Helper so that they point to the Windows DHCP server.

Apply QoS.

 

[tlpeter]

I did suggest using vlan's


BAZINGA!

I'm not insane, my mother had me tested!

 

[telgeek1]

anybody want to make a post letting us old timers know the difference between vpns and vlans? if any? also sip lines. sorry small town kid with a butt set and an awesome set of screw drivers

 

[tlpeter]

vlans are jsut multiple lans created on a network.
When you do not have vlans then you have a router, a switch and devices.
With vlans you still have the same network but virtually devided in multiple lans (vlan = virtual lan)
The vlan gets an ID and you need to program the devices or tell the devices to use this vlan (tagged)
When the devices won't understand that then it must be configured that this is not needed (untagged)

VPN is virtual private network -> you are using a non private network where you build a private network on with a tunnel (and security on it)

SIP is a protocol used for trunks and devices to communicate.


BAZINGA!

I'm not insane, my mother had me tested!