Re: DHCP Option 82

Hi Keith,

It really makes me feel proud when people like you give me a boost! Hard
work hopefully will continue more & more, and everyday when I learn some new
concepts, I come to know how much I still don't know..

Thank You Keith!

KJ

On Fri, Oct 30, 2009 at 1:35 AM, Keith Barker <kbarker_at_ine.com> wrote:

> KJ-
>
> Excellent job. Thank you for taking the time to explain that for everyone
> on GS. With all the fighting going on there, it is nice to see some
> genuine help. Keep up the great posts.
>
> Thanks,
>
> Keith H. Barker, CCIE #6783
> Senior CCIE Instructor
> http://www.INE.com <http://www.ine.com/>
>
> Internetwork Expert, Inc.
> Toll Free: 877-224-8987
> Outside US: 775-826-4344
>
> On Oct 28, 2009, at 12:54 AM, karim jamali wrote:
>
> Hi,
>
> DHCP option 82 is an optional feature that allows the relay agent to insert
> circuit specific information into a request being forwarded to a DHCP
> server. This option 82 information can be used by the DHCP server to
> implement policies (allocation of addresses based on the requesting subnet
> (giaddress) as well as the circuit-id information (e.g: Port on the switch
> on which the client resides). For instance, you can have 12 clients on a
> common VLAN, and you would like to give 6 of them from a certain range
> within the pool, and the other 6 clients from another range in the pool
> based on the circuit-id (tied to the switch interface).
>
> For instance:
> You can create a pool for a subnet (172.16.12.0/24), within the pool you
> can
> create classes. Each class will have a range of option 82 values, which
> will
> match a range of circuit-ids of the client ports. Thus a client connected
> to
> a certain port, the circuit-id of that port will determine to which class
> the client belongs to and thus will issue the client an ip address from a
> certain range within that pool. (172.16.12.1 - 172.16.12.20).
>
> So the circuit-id matches option 82 hex value corresponding to the class
> which in turn corresponds to a range of ip addresses within the
> subnet(pool).
>
> Sample Configuration(Cisco's Website):
>
> Defines the DHCP classes and relay information patterns
>
> ip dhcp class CLASS1
>
> relay agent information
>
> relay-information hex 01030a0b0c02050000000123
>
> relay-information hex 01030a0b0c02*
>
> relay-information hex 01030a0b0c02050000000000 bitmask
> 0000000000000000000000FF
>
>
> ip dhcp class CLASS2
>
> relay agent information
>
> relay-information hex 01040102030402020102
>
> relay-information hex 01040101030402020102
>
>
> ip dhcp class CLASS3
>
> relay agent information
>
>
> ! Associates the DHCP pool with DHCP classes
>
> ip dhcp pool ABC
>
> network 10.0.20.0 255.255.255.0
>
> class CLASS1
>
> address range 10.0.20.1 10.0.20.100
>
> class CLASS2
>
> address range 10.0.20.101 10.0.20.200
>
> class CLASS3
>
> address range 10.0.20.201 10.0.20.254
>
>
>
> For more information on this topic check:
>
> http://blog.internetworkexpert.com/2009/07/22/understanding-dhcp-option-82/
>
> http://www.faqs.org/rfcs/rfc3046.html
>
> Best Regards,
> On Wed, Oct 28, 2009 at 10:30 AM, Antonio Saez <
> antonio.saez.jimenez_at_gmail.com> wrote:
>
> Hi all,
>
>
>
>
> I am Reading the doc about dhcp option 82 and not sure I understand it
>
> completely. What is it used for? Is needed for dhcp snoop feature?
>
>
> Sorry for these basic questions but do not have switches to test it.
>
>
>
>
> Thanks all
>
>
>
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> --
> KJ
>
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-- 
KJ
Blogs and organic groups at http://www.ccie.net