DHCP client's IP release query Post: 302693067

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Special Forums IP Networking DHCP client's IP release query Post 302693067 by Corona688 on Tuesday 28th of August 2012 02:17:36 PM

08-28-2012

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Quote:

Originally Posted by satish51392111

1. If a new client comes up and it needs an IP to be assigned by a DHCP server, how can it communicate with the DHCP server in the first case without any IP? The SUN doc says something about "BOOTP" agent but could not understand it. Can anyone enlighten me here??

Remember that ethernet can carry more than one kind of protocol; in the end it's just another level of frame. You can still broadcast without an IP, using your MAC address. The DHCP server can broadcast back.

Quote:

2. What would happen if the client was shutting down and it sent a 'IP release request' (to the DHCP server which provided its IP) but the DHCP server in question was unavailable?

Then the DHCP server wouldn't get the message, and would consider the IP to still be occupied.

Eventually it would time out, not being renewed, and be considered free again by the DHCP server, and possibly given to someone else should a request be made.

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LEARN ABOUT CENTOS

dhcp_release

DHCP_RELEASE(1) 					      General Commands Manual						   DHCP_RELEASE(1)

NAME

       dhcp_release - Release a DHCP lease on a the local dnsmasq DHCP server.

SYNOPSIS

       dhcp_release <interface> <address> <MAC address> <client_id>

DESCRIPTION

       A utility which forces the DHCP server running on this machine to release a DHCP lease.

       Send a DHCPRELEASE message via the specified interface to tell the local DHCP server to delete a particular lease.

       The  interface  argument  is  the interface in which a DHCP request _would_ be received if it was coming from the client, rather than being
       faked up here.

       The address argument is a dotted-quad IP addresses and mandatory.

       The MAC address is colon separated hex, and is mandatory. It may be prefixed by an address-type byte followed by -, eg

       10-11:22:33:44:55:66

       but if the address-type byte is missing it is assumed to be 1, the type for ethernet. This encoding is the one used in dnsmasq lease files.

       The client-id is optional. If it is "*" then it treated as being missing.

NOTES

       MUST be run as root - will fail otherwise.

LIMITATIONS

       Only usable on IPv4 DHCP leases.

SEE ALSO

       dnsmasq(8)

AUTHOR

       This manual page was written by Simon Kelley <simon@thekelleys.org.uk>.

																   DHCP_RELEASE(1)