IP Phones by Location?

[Moshimoshi]

Hi folks, me again - still trying to wrap my brain around yet (another) IP change for Telecom gear in my company, but I think I have a better idea of whats going on this time. Just a matter of dialing in what the new IP's will be, and what dependencies they have that need to be updated. However, one thing gave me a bit of a quirk.

I understand that you use a DHCP 176 line for 46XXOPTION settings, to tell it what CLAN to reach out to, what TFTP, etc.

But the way corporate wants this done is that all IP Telephony is to be a 10.200.vvv.xxx, where "vvv" is the locations IP range, and xxx is the Statid or DHCP address.

some examples are:

10.200.89.(???) For Phones at X retails
10.200.78.(???) For Phones at Y office
10.200.67.(???) For Phones at Z Warehouse

If I only have one DHCP line to define...can someone give me a quick break out to make sure that the phones in each locationa are grabbing the proper DHCP address space?

We have a pretty competent Network support crew, which is great, I just am not understanding how each location's IP phones would figure out that they have a 'different' range than their neighbor. Hope this makes sense.

~Sean
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Telecom Analyst, FOI.\\\\_______________

 

[optionsleft]

In DHCP 3 scopes should be created having each VLAN ID (X,Y,Z) and option 176 should be define in each scope respectively.

 

[Mitch672]

In your ethernet switches, they would have an "IP Helper" address defined, this tells the switch where to go for the DHCP server. Your switches are defined by VLANs that have specific IP ranges to each VLAN, so the request goes out for an IP address in that VLANs range, to the IP Helper DHCP server defined. If there is a DHCP Scope defined in that IP range, the DHCP server gives out an IP to a device requesting it.

Google "DHCP IP Helper" if you need more.



Mitch

AVAYA Certified Expert

 

[Moshimoshi]

Optionsleft:

Hmm...I think I get what you're saying, but I'm sort of curious. We have a range of scopes already in place for our Data network [10.150.xxx.xxx] (same locations we now want to add 10.200 VOIP stuff) would I create additional 10.200 scopes? Ah maybe I'm thinking about this too hard.

Mitch:

That makes sense, and I'm starting to wonder if maybe it would be prudent to keep a second DHCP server for VOIP stuff that I manage on a central Telecom server (which I'm considering anyhow, for a variety of network hosted telecom Administrative stuff, like VOIP Mon. Mgr.). At that point, the IP helper would just point to said server on all of the switches, correct?

And then just define all the Scopes with 176 lines for their appropriate MCI, and the scope itself will set it properly for its location?

~Sean
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Telecom Analyst, FOI.\\\\_______________

 

[Mitch672]

Option 176 for 46XX IP phones
Option 242 for 96XX IP phones

Yes, if you control the DHCP server, then when you need to change something, you can

You can also see if a phone is being given an address, etc, it's handy to have access to the DHCP server.



Mitch

AVAYA Certified Expert

 

[Moshimoshi]

Hmm, so I take it, if I brought my own DHCP server online, we would take the 176/242 lines out of the scopes/server options for the 10.150 DHCP server

And then on the new DHCP server, recreate the same DHCP scopes but with 10.200 addresses, and re-add the 176/242 options to these scopes?

And then all of the switches would get their IP Helper addresses fixed up so that a broadcast from the phones for DHCP would direct to the 10.200 DHCP Server (or individual Scopes) and acquire their address there, then pull the 176/242 line?

*breath* Okay did I miss anything? If not, this sounds almost too easy.

~Sean
-----------------------
Telecom Analyst, FOI.\\\\_______________

 

[Mitch672]

Your data people are most likely going to have a problem with that. You can only have 1 DHCP Helper per VLAN segment, so it's either IP phones or Data (PCs), there are other ways to get fancier, and to share the port on the back of the phone for PC's, but that's another discusssion.

Remember: 1 DHCP Helper server per VLAN



Mitch

AVAYA Certified Expert

 

[manfmmd]

Remember: 1 DHCP Helper server per VLAN
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Not true depending on how you have your network setup. We have 2 ip-helpder addresses setup on the vlans that are assigned 'switchport access vlan' and 1 ip-helper address on the 'switchport voice vlan' side.

It all depends on how flat your netowrk is.

 

[Mitch672]

Yes manfmmd, I said there WHERE ways to get fancier, we are trying to get the basics down here first. If you have multiple VLANs, yes, that is getting fancier, isn't it?

That leads into getting the downstream IP phone LAN port on its own VLAN, so you can put a PC on it, and have its own DHCP server scope etc.

I have set this up for clients before, and many are looking to do it to save:

1) ethernet switch ports, only takes 1/2 the # when the port is shared between PC and Telephone

2) Wiring: you only need a single cable for the users PC and Phone, saving money if you are wiring a new space.





Mitch

AVAYA Certified Expert