DHCP 4x MCD Systems

[cloudbased]

A customer mentioned that they would want another 3 MCD systems for some more users they have planned.

Currently they have one DHCP server with option 125 pointing to their primary MCD system facilitating their current users with 6 voice VLANs for phones. They use HP switches with IP helpers.

They would add the extra 3 MCD systems into the same voice server VLAN as the current MCD system.
They would add another 6 VLANS per extra MCD system, so an extra 18 VLANS in total.

How would they program their DHCP server options so that phones booted off their native voice VLANS register with their respective MCD controllers not just the current one?

i.e:

Voice Server VLAN 10 = 4 x MCD systems
Voice Phone VLAN 80 = Phone registers to System A
Voice Phone VLAN 90 = Phone registers to System B
Voice Phone VLAN 100 = Phone registers to System C
Voice Phone VLAN 110 = Phone registers to System D

Gracias

 

[bobcheese]

what is issuing DHCP at present?

 

[cloudbased]

Their MSL Server which lives on VLAN 10.

They want to use their Win 2008 AD server though going forward, however that is a different project they have planned.

 

[bobcheese]

cant comment on MSL server as I never use it for DHCP. However, i mimagine it would be similar to 3300 whereby you create multiple scopes for the correct subnet and the switches have iphelper configured. So when a DHCP request comes from a certain VLAN (via a subnet gateway) the DHCP server looks for a matching subnet to the gateway the request came from. If it finds a match it will issue an address from that pool.

Like i said this is how the 3300 works so someone will need to confirm for MSL

 

[kwbMitel]

Using IP Helper is a little archaic

The HP switches should be configured for LLDP so that the phone can Discover directly on the specific Vlan

At that point it is easy to provide the appropriate scope options. (Per Vlan)

**********************************************
What's most important is that you realise ... There is no spoon.

 

[mitelmitel]

I got it wrong LLDP is enabled so phone boots straight to designated VLAN.

So each scope for vlan would need options to point to the designated MCD system?

 

[kwbMitel]

Yeah, that's about it.

Last I checked the MCD can handle 10 Scopes all by itself if you want.

**********************************************
What's most important is that you realise ... There is no spoon.

 

[kwbMitel]

Just checked because I thought this had changed

It is now 50 Subnets

**********************************************
What's most important is that you realise ... There is no spoon.

 

[mitelmitel]

Just checked their config.

So we would simply add an option 125 for every phone VLAN populating the VLAN ID field. I.e

Option 125:
TFTP Server Address: "system A IP"
Call Server Address: "system A IP"
VLAN ID "80"

 

[LoopyLou]

Correct. If you had of used the 3300 for your DHCP you create the subnets ( up to 50 as kwbMitel points out ) and when you do option 125 you can make it global to apply to all subnets or you can assign the option 125 to a particular subnet. As long as you can duplicate it on the MSL you should be ok.

Now that said, even if you used a single Option 125, it all figures it out anyway i.e if you have a single option 125 pointing to system A the phones on system B will look their first but then go to system B. The cluster programming allows every 3300 to know where a particular phone should go. It is however faster to create the seperate option 125's because if you send everything to one system then all the phones end up doing TFTP to get their first firmware.

P.S they always want to use their own DHCP servers so they have CONTROl!. However why they want to expose their voice LAN to another point of failure when the 3300's can do DHCP just fine is beyond me. You can still use the 2008 server and AD to "hook" into the 3300 cluster and voicemail to program users. No need to do DHCP on it. At least the 3300 can be setup to bar anything on the voice VLAN that is not a phone to get an IP address. Not sure the 2008 DHCP can do the same thing.

I'd tell you a UDP joke but I'm afraid you won't get it. TCP jokes are the best because you always get them.

 

[mitelmitel]

Thank you for the help, very informative.

 

[bobcheese]

@ KWBmitel, even if the switches sue LLDP to discover the correct voice VLAN (depending on which PBX they are on they could be on one of many). None of the phone VLANs have a DHCP on them so iphelper is needed to point them to 1 VLAN which has the DHCP on it.

 

[kwbMitel]

@bobcheese
On every site that I have done this, the DHCP is enabled on each of the Vlans, IPhelper not required.

Last time I used IPhelper was about 5 years ago.

**********************************************
What's most important is that you realise ... There is no spoon.

 

[LoopyLou]

depends on the setup. Need the helper if there is any routing involved.

I'd tell you a UDP joke but I'm afraid you won't get it. TCP jokes are the best because you always get them.

 

[bobcheese]

hence my post. The phone are never on the same L2 network as the controller

 

[LoopyLou]

Agreed most phones are on a number of seperate VLAN's and rarely on the same VLAN as the 3300 unless a single 3300 and a very small implementation. Also you don't typically want to put more then 200 IP devices on a subnet so more then 200 IP sets will alwasy be multiple VLANs.

In this case its 4 3300's so it is even more unlikely that its on a single VLAN so IP helper is still valid.

I'd tell you a UDP joke but I'm afraid you won't get it. TCP jokes are the best because you always get them.

 

[bobcheese]

@ LoopyLou I am curious as to why you would say no more than 200 phones on a subnet?

 

[LoopyLou]

There is some document I recall reading that said on a class C subnet it is best practices to have no more then 200 devices. That's where I go it from. Maybe it was bollocks.

I'd tell you a UDP joke but I'm afraid you won't get it. TCP jokes are the best because you always get them.