IP destination address for DHCPOFFER?
Glenn.Satchell at uniq.com.au
Tue Jun 26 13:22:39 UTC 2007
You could try this option. It's a grey area, the client is supposed to
request that responses be broadcast but not all do, so the dhcp server
gives you the each way option.
The always-broadcast statement
The DHCP and BOOTP protocols both require DHCP and BOOTP
clients to set the broadcast bit in the flags field of the
BOOTP message header. Unfortunately, some DHCP and BOOTP
clients do not do this, and therefore may not receive
responses from the DHCP server. The DHCP server can be
made to always broadcast its responses to clients by set-
ting this flag to 'on' for the relevant scope; relevant
scopes would be inside a conditional statement, as a
parameter for a class, or as a parameter for a host
declaration. To avoid creating excess broadcast traffic
on your network, we recommend that you restrict the use of
this option to as few clients as possible. For example,
>Date: Tue, 26 Jun 2007 14:07:37 +0200
>From: "Dan Sahlin" <dan.sahlin at raycore-fos.com>
>What is the proper IP destination address for a DHCPOFFER message?
>ISC DHCP v3.0.4 uses the new proposed IP address as the destination
>address in the DHCPOFFER message, i.e. the same as the yiaddr.
>One DHCP client I have (a managed fiber converter) ignores this
>DHCPOFFER message as it expects the broadcast IP adress (
>In "The DHCP Handbook" on top of page 107 the DHCPOFFER destination
>address is shown as the broadcast address. However, the text on the
>same page says:
>"This message is sent to the Ethernet broadcast address
>ff:ff:ff:ff:ff:ff and to the new assigned IP address 192.168.11.25."
>I do not find the RFC2131 very clear either regarding the proper
>addressing of DHCPOFFER. In section 3.1.2 it simply says
>"Each server may respond with a DHCPOFFER message that includes an
>available network address in the 'yiaddr' field..."
>So how should the standards properly be interpreted regarding the IP
>and MAC adresses of the DHCPOFFER message?
> /Dan Sahlin
>email: dan.sahlin at raycore-fos.com
>phone: +46 70 5198187
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