Hi All,
This is Sathya, a debian etch user who uses dhclient package to configure
the IP address.
Firstly, I would like to give my heartily thanks to you all for your great
dedicated contribution towards this package. As I am newbie to this mailing
list, I am not aware on where to post this query. So, thought of this mail
directly sending it to you all.
My system has following dhclient packages,
ii dhcp3-client 3.0.4-13+etch2 DHCP
Client
ii dhcp3-common 3.0.4-13+etch2 Common
files used by all the dhcp3* packages
ii dhcp3-server 3.0.4-13+etch2 DHCP
server for automatic IP address assignm
Following is the problem which I am facing now,
I have a subnet whose IP addressing is managed by DHCP server. But, one
system in that is intentionally assigned a static IP address. In multiple
occasions, I am now getting IP conflicts in my subnet.
On further analysing this problem, I could undertand that this probelm is
happening because,
1. As DHCP server is un-aware of this statically configured system; upon
receiving the DHCPREQUEST from a system (which is running dhclient)
from this subnet, the DHCP server gets an unused IP from its IP pools offers
it to that client. *In somecases, dhcp server is giving the same IP address
as that of statically configured system. *
2. As on receiving the IP address, *our dhclient is not performing a final
check on the existence of IP conflict for prior received IP address using
ARP broadcast,* it goes ahead in configuring the system with this IP
address. This results in an IP conflict to exist between these two systems
(with this system and a system with statically configured IP).
*I could also see that, our debian dhclient presently DOES NOT HAVE AN
OPTION TO IMPLICITLY SUPPORT THIS.*
But as per RFC 2131, the client should perform a final check to detect the
IP conflict and send DHCPDECLINE message. Please find the RFC snippet as in
below,
"5. The client receives the DHCPACK message with configuration
parameters. *The client SHOULD perform a final check on the
parameters *(e.g., ARP for allocated network address), and notes the
duration of the lease specified in the DHCPACK message. At this
point, the client is configured. *If the client detects that the
address is already in use (e.g., through the use of ARP), the
client MUST send a DHCPDECLINE message* to the server and restarts
the configuration process."
And also I could find the following information on dhclient manpage
regarding this,
" Before actually configuring the address, dhclient-script should
somehow
ARP for it and exit with a nonzero status if it receives a reply.
In
this case, the client will send a DHCPDECLINE message to the server
and
acquire a different address. This may also be done in the
RENEW,
REBIND, or REBOOT states, but is not required, and indeed may not
be
desirable."
As changes to DHCP server is out of our control & we are not sure on what IP
would be statically configured to the system, could you please let me know
your thoughts on how do this we can fix this in dhclient code to
automatically detect duplicate address using ARP broadcast ?
If this support this not there in present dhclient, could you please let me
know by when this the community planning to give a patch for this.
As I am in need of urgent need for fix on this issue, it would be really
helpful if I can get your thoughts on this by earliest.
Thanks a lot in advance for understanding.
Regards,
Sathya
