[dhcwg] <draft-ietf-dhc-agent-subnet-selection-03.txt> - Classfull ?

Van Aken Dirk <VanAkenD@thmulti.com> Tue, 08 October 2002 20:59 UTC

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From: Van Aken Dirk <VanAkenD@thmulti.com>
To: "'dhcwg@ietf.org'" <dhcwg@ietf.org>
Cc: Dedecker Hans <DedeckerH@thmulti.com>, Dekeyser Miek <DekeyserM@thmulti.com>
Date: Mon, 07 Oct 2002 10:14:18 +0200
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Subject: [dhcwg] <draft-ietf-dhc-agent-subnet-selection-03.txt> - Classfull ?
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Hello Working group,

Could it be that the "Link Selection sub-option for the Relay Agent
Information Option" is a classfull option ?
i.e. According this draft, the format of the sub-option is:

           SubOpt   Len     subnet IP address
          | TBD  |   4  |  a1  |  a2  |  a3  |  a4  |

The sub-option contains a single IP address that is an address con-
tained in a subnet. The value for the subnet address is determined by
taking any IP address on the subnet and ANDing that address with the
subnet mask (i.e.: the network and subnet bits are left alone and the
remaining (address) bits are set to zero).

If I understand the above text correctly, a single (masked) IP address is
added to this sub-option by the relay agent and submitted to the DHCP
The latter will subsequently supply an address within the same subnet.

I wonder though how the DHCP server can derive a subnet from a single
quantity being an IP address. e.g. can be an alias for
So my guess is that the only way the DHCP server can derive the subnet form
is based on the leading bits of the address being either class A, B or C.

Am I correct ?

Thanks in advance - Dirk

Dirk Van Aken                              THOMSON multimedia Broadband
Belgium NV
System Architect                           Prins Boudewijnlaan 47,
Tel. : 03/443.65.08                        2650 Edegem
Fax.: 03/443.66.32                         Belgium

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