[SIPForum-discussion] IP PBX _Asterisk

Rohan Almeida almeida.rohan at gmail.com
Mon Aug 29 13:21:19 UTC 2011

Hi Yusof,

The Access layer of IMS contains *NACF* (Network Access Configuration
Function) which is nothing but enhanced *DHCP*. IP telephones and all other
User Access Equipment (UAE) get their  IP addresses from NACF.

Pre-Registration activity of the User agents consists of getting the IP
address(If not statically configured). This is done using DHCP discover
message. When a user powers on the UAE, device will broadcast DHCP discover

In the most of  the cases that broadcast message will not go directly to the
IMS core. Some relay-agent  (probably default gateway or DSLAM) will hear
the DHCP Discover message and it will pass  through as unicast to the
NACF.Additionally, Relay agent will insert DHCP option 82 and in  that case
IMS core will know exact location of UAE.

The option 82 contains circuit specific information into a request that is
being forwarded  to a DHCP server.the option works by setting two
sub-options: Circuit ID and Remote ID.

The* Circuit ID* sub-option is supposed to include information specific to
which circuit the  request came in on. It's an identifier that is specific
to the relay agent.

The *Remote ID* sub-option carries information relating to the remote host
at the end of the  circuit. In practice, this sub-option contains
information that identifies the relay agent.  In the case of an Ethernet
network, this is the MAC address of the relay agent.
Rohan Almeida
On Thu, Aug 25, 2011 at 11:30 PM, lubao <lubao at eastcom.com> wrote:

> **
> Dear all,
> Who knows Aserisk IP PBX well?
> 2011-08-26
> ------------------------------
> Gabriel Lu
> *Eastern Communications Co. Ltd.
> *IPS&TPlus
> ,the power of your VAS system.
> ====================================
> ======================================================
> Office: +86-571-86675211 FAX:+86-571-86698523
> Mobile: +86-15158102829
> Add:
> B344, R&D building, NO.66, Dongxin Road, Hi-Tech Development Zone,
> Hangzhou, China, 310053
> Please visit our web:
> VAS Brand website:              http://vas.eastcom.com
> Eastcom's portal website:  http://www.eastcom.com
> ------------------------------
> *发件人:* ridhuan yusof
> *发送时间:* 2011-03-29  23:38:00
> *收件人:* discussion
> *抄送:*
> *主题:* [SIPForum-discussion] dhcp option 82
>  Folks,
> Can u explain what is dhcp option 82 in IMS?
> Rgds,
> Ridhuan
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