Migrating to Windows DHCP Server

[mitelmitel]

I am using Mitel for our DHCP services. I have 5 Voice VLANS.

We have HP swicthes that have IP Helpers pointing the phones to the correct VLAN/DHCP server.

I need to migrate the voice DHCP services from Mitel to our Windows DHCP server, whats the best practice? and can I use the same options:

Option 6NS
Option 125: Mitel
Option 3: Router

Thanks

 

[LoopyLou]

Can I as why? Just Curious.



The single biggest problem with communications is the illusion that it has taken place.

 

[Supernova99]

you can easily have 5 voice vlan scopes running from the 3300 controller
If you really want to do this i suggest enabling LLDP on the HP switches and then the phone will only get 1 IP address and not 2
I have attached the windows 2003 DHCP helper config tool if you want to configure it that way


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[mitelmitel]

I am using a now redundant MSL server for Mitel DHCP, and want to re-utilise that server for another purpose within my infrastructure.

I suppose I could use one of our 6 gateway MXe 3300s for DHCP, however 'eggs in one basket spring to mind'.

 

[Supernova99]

you could split the DHCP ranges across multiple 3300 controllers then if you have a failure one of the others can still issue an IP address
When using multiple controllers I never use just one controller to issue DHCP for you exact fears

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[mitelmitel]

Thanks Supernova. At the moment the phone boots straight onto the correct VLAN [configured on the HP Switch] then the helper sends it to the MSL server.

 

[Supernova99]

so you already LLDP configured so you just need to change the helper address to point to the 3300 and then setup the DHCP scopes for those vlans

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[mitelmitel]

Hmm, what about resiliency? I haven't currently enabled resiliency but it will be soon, what if the gw falls over? Shall I simply program another dhcp server with different ranges on another gw but disable it until it fails over then change the helpers to point to the secondary gw on demand?

 

[Supernova99]

you can put the resilient contollers into the option 125 (up to 4 icp's) you can also split the ranges across a couple of controllers.
e.g. If your subnet is 255.255.254.0 then you have approx 500 addresses to use. You can program first 250 on the primary controller and the second 250 on the resilient controller

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[mitelmitel]

Thanks so that configuration would be suffice for 250 phones?

To throw things into the mix my users are on a user gateway (not listed above) on a mce server. I am buying another one for resiliency soon. As stated my dhcp is on an msl server. Would you still think it would be best to use my gateways for dhcp?

I have 500 phones

 

[Supernova99]

DHCP is not supported on the MXe server so splitting the range across 2 gateways will be the way to go I think
If you have 500 and it will not increase then subnet to 255.255.254.0 if it will grow then subnet a little further 255.255.252.0 this range will give you around 1000 addresses so just split the range 50/50 between gateways

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[mitelmitel]

I suppose in your scenario of one of the gateways failed then the phones assigned to it via DHCP would not get an IP if the phones rebooted or lease run out, but the other half would be OK.

I would ideally need a solution where I could get 100% uptime for all phones regrading DHCP, a blip would be OK.

 

[Supernova99]

If you have assigned a range big enough then, the phone if rebooted will get an address from the secondary server.
DHCP addresses will be issued via both boxes as it is the first server to respond to a request that will give a lease.
If all leases are used on the server the secondary server will be able to respond to the request.

So If you need to reboot phones when the primary controller is down I suggest subnetting to 255255.252 and then when you split the range across both servers each can handle 500 leases

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[mitelmitel]

I have 5 Vlans for voice:-

192.168.120.x
192.168.121.x
192.168.122.x
192.168.123.x
192.168.124.x

All for different areas of the business, and on a 255.255.255.0 subnet.

Voice servers and 3300s are on the 120 VLAN.

Does the IP Helper on the HP Switches dump the phone in the correct VLAN so that it can get an IP [i.e. VLAN 120]? Thats my understanding?

So if it points it into the 120 VLAN it will then get an IP from the Voice DHCP server, the DHCP server sees what the HP Switch Port the phone has been tagged it to [Phones VLAN] and then assigns it an IP from that particular range, i.e. an IP from the 123 VLAN range if it booted up in that area.?

If there are 2 DHCP servers then they will share the load.

Sorry if I am sounding very basic with the above.