Nortel IP telephony and NAT

[alexd007]

Hello Nortel/Avaya gurus,

Network guy here, trying to find out if a Nortel IP telephony system should work with NAT between the phones and the signaling server. To be clear, let's say I have this right now:

Untrusted Phones 10.1.1.10-20 --> [Firewall] --> Signaling server 10.10.10.10 and internal phones

Everybody can call everybody in this setup (untrusted to internal, untrusted to untrusted, etc.)

And then one morning I activate  one-to-one NAT between the phones and the signaling server, like so:

Untrusted Phones 10.1.1.10-20 --> [Firewall NATs phones to 10.99.99.10-20] --> Signaling server 10.10.10.10 and internal phones

DHCP queries aren't affected by the natting (dhcp server resides on the left of the firewall).

Will this work ? Will the untrusted phones still be able to register in the signaling server ? Will they be able to call each other (untrusted to untrusted) ? Will an untrusted phone still be able to call an internal phone (right side) ?

I just want to know if NAT is supported in a Nortel IP telephony infrastructure. I DON'T want to do this (I hate NAT with a passion), so this is my "plan D", in case all else fails and I'm stuck

Thanks for the help!

Alex.

PS : Sorry if this has already been answered, but I did a quick forum search for "nortel NAT" and got nothing.

[Michael McNamara]

Hi Alex and welcome to the fourms!

What model of IP phone are you referring to?
What version of software are you running?
What model/version of Communications Server are you using?
Are you using UNIStim or SIP?

In general NAT will not work between an a legacy IP phone and a Call Server. With that said there have been a lot of changes in the past few years to support NAT but that will all depend upon which IP phone (software) you are using all with the Call Server.

I would recommend searching Avaya's website;
http://www.google.com/search?q=support%3Asupport.avaya.com+phone+nat

Good Luck!

[alexd007]

Hello Michael, and thanks for the quick answer!

Our setup : Nortel 1140E and 1150E running 0625C6N, on a CS1000M running Succession 4.5.

So I guess we are pretty much legacy ?

There is an upgrade to Succession 6 coming soon, do you think that will change the picture ?

Thank you!

Alex.

[alexd007]

Friendly bump 

[Michael McNamara]

Hi Alex,

Have you reviewed the manuals? The Communication Server 1000 v4.5 IP Phones NTP (http://support.avaya.com/css/P8/documents/100100191) page 553 has the following references on NAT Traversal;


Network Address Translation Traversal

This section describes the Network Address Translation (NAT) Traversal feature as it effects IP Phones. NAT Traversal is required to permit IP Phones working behind a NAT box to connect and maintain signaling and media paths.

NAT Traversal is applicable to all UNIStim IP Phone clients and is oneended. That is, it does not require the other end of a call to support any special protocol, and it is interoperable with any other media termination. In this document NAT refers to both IP port address mapping and IP address mapping (also known as NAPT). A NAT can be used with or without a Virtual Private Network (VPN).

The NAT Traversal feature supports only IP clients behind cone NAT types. There are three types of cone NAT—the full cone, restricted cone, and the port restricted cone. NAT traversal is not compatible with symmetric NATs. If the IP Phone is behind a Symmetric NAT, the LTPS unregisters the phone from the call server (while remaining registered on the LTPS), and displays the following message on the IP Phone display: “Error! Symmetric NAT”.

For detailed information about the NAT Traversal feature, see IP Line: Description, Installation, and Operation (553-3001-365).
For information about accessing NAT information from an IP Phone, see “Set IP Information” on page 555.

Cheers!

[alexd007]

Thanks for the links Michael!

Altough Nortel uses the "Cone NAT" terminology which is really confusing, I was able to find many answers in the document you provided. Also, in one document refered by yours (IP Line
Description, Installation, and Operation, #553-3001-204, page 77), it was clearly stated that two IP phones behind the same NAT box could not call each other... this is a show-stopper for me so I won't be going any further.

Thank you for the great references Michael, I appreciate it!

Have a great day,

Alex.

[Michael McNamara]

I'm happy that we were able to help!