DHCPINFORM via a relay agent
sasaki at fcc.ad.jp
Mon Aug 21 05:24:19 UTC 2006
From: "David W. Hankins" <David_Hankins at isc.org>
Subject: Re: DHCPINFORM via a relay agent
Date: Sun, 20 Aug 2006 15:47:13 +0000
> This is a compounded bug. Existing code that attempted to work with
> clients that specify a ciaddr of 0.0.0.0 was 'enhanced' to deal even
> better with them. In the meantime, we appear to have brkoen clients
> that specify non-zero ciaddr via relays.
> You will have noted from your careful reading of rfc already that
> such zero-ciaddr-DHCPINFORM clients are already not implementing
Do you mean that this is zero-ciaddr-client-handling issue?
The following scenario describes my question.
Client has an IP Address CCC.CCC.CCC.CCC which has been assigned by
server. Relay agent has two IP Addresses, GGG.GGG.GGG.GGG (client
side) and XXX.XXX.XXX.XXX (server side). Server has an IP Addresses
SSS.SSS.SSS.SSS. Client is MS windows XP. Server and relay agent
1. Client broadcasts DHCPINFORM.
ip src CCC.CCC.CCC.CCC
ip dst 255.255.255.255
2. Relay agent receives the message and relays the following to the
ip src XXX.XXX.XXX.XXX
ip dst SSS.SSS.SSS.SSS
3. Server receives the message and replies the following to the relay
ip src SSS.SSS.SSS.SSS
ip dst GGG.GGG.GGG.GGG
The ISC dhcpd always replies to giaddr if it has giaddr. I guess
that the server should send the DHCPACK reply to the client
4. Relay agent receives the reply message and relays to the 0.0.0.0.
ip src GGG.GGG.GGG.GGG
ip dst 0.0.0.0
The ISC dhcrelay always forwards the reply message to yiaddr if it
has no broadcast flag.
Is it wrong to send the DHCPACK reply to ciaddr instead of giaddr
whether the DHCPINFORM has giaddr?
Fusion Communications Corp.
Kan Sasaki sasaki at fcc.ad.jp
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