Multiple Vlan with one DHCP from 3300

[louisesmith]

Hello,

We have DHCP enable in 3300 in Vlan 2 and this site have 5 floors and each floor will have difference Vlan (vlan 2-6) and different subnets. I know I need to create 5 scope option 125 for 5 different subnets in the phone system.
My questions is, the port that the PBX connects to will need to be program as untagged port in Vlan 2 or trunk port Vlan 2?
How will the phones from different vlan will know how to connect to 3300 in Vlan 2?

Thank you

[sarond]

Basically there will be DHCP Helpers/Forwarders that forward a DHCP request for that specific VLAN to a DHCP Server, in your case the 3300.
You will also need to ensure routing is in place between the VLANs. You need to set up DHCP Options per scope on the 3300. When the switches forward the request to the 3300 it will know which scope to respond to and give the options specified.

The 3300 can be in any VLAN, I would just leave as is for now. Leave the port as it is, the switches will take care of the VLAN tagging for the rest of the network.

It sounds more complicated than it really is.

[ralph]

Here's a link that may help with some more info on DHCP Helper.

www.freeccnaworkbook.com/workbooks/ccna/configuring-an-ip-dhcp-helper-address

Ralph

[louisesmith]

Thanks Sarond.

If the PBX is connected to an untagged vlan 2 port and DHCP helper/Fowarders that forwards phone on the 5th floor to vlan 5, how will the phones connect to the PBX in Vlan 2 to get an IP address? I am a bit confuse.

Thanks

[sarond]

The DHCP Options will be different for each VLAN.
They each have their own options for Router and Option 125 as a minimum.

As long as the vlan/phones can then route to the 3300 then there should be no problem.

[louisesmith]

Hi Sarond,

I understand what needs to be done in The PBX end.
If the phones on the 5th floor is assign to go to vlan 5 by the DHCP helper, it will work eventhough the PBX is in Vlan 2?

What I don't understand is if the phones on the 5th floor goes to vlan 5, how does it go to vlan 2 to get an IP address from the PBX?
DO I just need to setup DHCP helper only or I need to setup LLDP also?

Thanks very much for your help

[sarond]

Don't think of it as how will my device get to VLAN 2, think of it as how will my device get to the 3300's network.
VLANs are just virtual networks to segregate the traffic.

Correct VLAN routing is how VLAN 5 will get to VLAN 2, if there is no routing between these VLANs then nothing is going to work. Most likely a router will handle the routing.

You could use LLDP to set the phone in to the correct VLAN although I'm not sure how this will work for multiple voice vlans on the same network. Normally there is only one voice vlan.

Why are there different VLANs for each floor? They are all connecting to the same 3300 anyway. Is there going to be a different vlan for each floor for data as well?

Lets say a phone on the 5th floor is either set to vlan5 statically or via LLDP when the phone boots into vlan5 and sends a DHCP request the helper will tell the phone where to go for an IP address and options. This will be your 3300, now as long as there routing in place where the phone can reach the 3300 it will get a response with all the options required.

Don't ask me how but the 3300 will know which network the phone belongs to e.g. 192.168.5.0/24 and this is how it knows which dhcp scope to use.

The switches will take care of all the VLAN stuff and as far as the 3300 is concerned it's just another network. Be aware that you will need separate Option 125 for each vlan because of the tagging required on the phones/switches.

e.g.
vlan2 option 125 - "id:ipphone.mitel.com;sw_tftp=192.168.0.2;call_srv=192.168.0.2;vlan=2;l2p=5;dscp=46"
vlan3 option 125 - "id:ipphone.mitel.com;sw_tftp=192.168.0.2;call_srv=192.168.0.2;vlan=3;l2p=5;dscp=46"
etc...

[louisesmith]

Thanks for your reply Sarond, your help is much appreciated.

They have different vlan for each floor because they might have over 200 IP phone per floor. Here is the network design,
Vlan 2: 10.10.2.x (PBX subnet)
vlan 3: 10.10.3.x
vlan 4: 10.10.4.x
vlan 5: 10.10.5.x
So for the phone on the 5th floor, in the DHCP helper, we just tell the phone to go to vlan 5 and to the PBX IP?
BTW, can we have one vlan for 5 floors ?

Thanks again for your help

[johnp]

You can have one vlan. Just change the subnet mask to 255.255.248.0 You would have a range of 10.10.0.0 - 10.10.7.254

[sarond]

As John says you can have 1 VLAN and is probably preferable. Just expand your netmask, this will make programming LLDP much easier.

A DHCP helper won't tell the phone which vlan to go to it will just give forward the request on a per network basis. Your vlan setup will need to be done statically or via LLDP, you could also setup a DHCP option on the native vlan if needed. Once the phone is in the correct vlan it will then request dhcp, the helper will just forward this request to a server (i.e. the 3300)

I'd recommend making your life easier and expand your network.

I'm no expert on large sites so maybe someone can advise whether expanding will have any issues.

[johnp]

The only issue I see would be that they may want to use a separate tftp server. With that many phones, I would think that if they need a flash update, it would take quite awhile.

[louisesmith]

So if have DHCP helper setup, I still need to setup LLDP/CDP?
I thought DHCP helper will tell the phone where to go and what vlan to go to?

[sarond]

No the DHCP doesn't tell the phone what vlan to belong to, it just serves options for a network.
VLAN setup will need to be done by other means, e.g. LLDP/CDP, static.

You can set up the options in the default vlans DHCP scope for the phone to get their vlan info.
Phone will boot into native vlan get options with new vlan id, phone will release DHCP lease and renew in new vlan.

[louisesmith]

So, with this all said.
I just need to assign one vlan (vlan 2) for all the phones, setup LLDP/CDP to boot to vlan 2 and setup DHCP helper in the switch for each floor to the proper subnet (shown below), right?
 
2nd floor, Vlan 2: 10.10.2.x/16
3rd foor, vlan 2: 10.10.3.x/16
4th floor, vlan 2: 10.10.4.x/16
5th floor, vlan 2: 10.10.5.x/16

Also, I will need to program 4 scope option 125 for each subnet with vlan 2?

vlan2 option 125 - "id:ipphone.mitel.com;sw_tftp=10.10.1.2;call_srv=10.10.1.2;vlan=2;l2p=5;dscp=46" 2nd floor
- "id:ipphone.mitel.com;sw_tftp=10.10.1.2;call_srv=10.10.1.2;vlan=2;l2p=5;dscp=46" 3rd floor
- "id:ipphone.mitel.com;sw_tftp=10.10.1.2;call_srv=10.10.1.2;vlan=2;l2p=5;dscp=46" 4th floor
- "id:ipphone.mitel.com;sw_tftp=10.10.1.2;call_srv=10.10.1.2;vlan=2;l2p=5;dscp=46" 5th floor

[sarond]

If you use one vlan (i.e. vlan 2) then every floor will be the same network. There won't be a way to get the IP addresses to be
10.10.2.x - floor 2
10.10.3.x - floor 3
10.10.4.x - floor 4
10.10.5.x - floor 5

They will just get the next IP address in the available range 10.10.x.x/16 in your example.

All you  option 125 scopes are the same so onlyu one would be needed.
As mentioned previously your 3300 is in vlan 2 already so once LLDP/CDP sets the phone to vlan 2 they will both be on the same network so no DHCP forwarders are needed. Forwarders will only be needed if there is no DHCP Server on the network/vlan. This way you can have one DHCP Server for multiple networks.

Is it essential to have the 10.10.floor.x address scheme? Everything will be much easier if not.