Re: DHCP Option 82

Hi Antonio,

I am not sure about this. Can you just give me the context in which you read
the relationship between option 82 and the port-security feature?

Thanks

Best Regards
On Wed, Oct 28, 2009 at 12:30 PM, Antonio Saez <
antonio.saez.jimenez_at_gmail.com> wrote:

> Thanks Karim,
>
>
>
> Ok I understand this, but why is needed for source guard port-security
> feature?
>
>
>
> Regards
>
>
>
> *De:* karim jamali [mailto:karim.jamali_at_gmail.com]
> *Enviado el:* miircoles, 28 de octubre de 2009 8:55
> *Para:* Antonio Saez; Cisco certification
> *Asunto:* Re: DHCP Option 82
>
>
>
> 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
>

--
KJ
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