dhcpd leases: abandonded

Mon May 3 16:39:10 UTC 2010

Message: 4

Date: Sat, 01 May 2010 16:39:26 +1000

From: Glenn Satchell <glenn.satchell at uniq.com.au>

Subject: Re: dhcpd leases: abandonded

To: Users of ISC DHCP <dhcp-users at lists.isc.org>

Message-ID: <4BDBCC9E.3050209 at uniq.com.au>

Thanks for the reply Glenn

"

An abandoned IP address is one that returns true to a ping before the

DHCPOFFER. Typically this is used in case some other device is already
using the IP address that is about to be offered."

This is not something I am seeing on my system - IP addresses marked abandoned do not reply to pings. Also, hosts cannot hear one another across the network, they can only communicate with a boundary router.

"If the dhcp server were to ignore the decline, then it would potentially

keep offering the same IP address to the client, which would decline, go

back to discover and so on in a loop. That probably won't help either. "

You are correct, that's exactly what I saw in testing. However, this did alleviate the original problem.

Let me restate my problem, in a different way:

> -client A declines its lease

> -client A discovers for a new IP

> -dhcpd marks client A's lease as abandoned

> -client A request/offer/ACK's

> -client B dhcpdiscover

> -dhcpd offers client A's IP address

> -client B starts a 4 hour DHCPDISCOVER/DHCPOFFER loop

Client A's MAC address remains in arp cache for the next four hours.

This symptom is repeated throughout my network - it's not just one client.

4 hours is a default arp time.

I am interested to know if there is a way to increase the amount of time an IP is marked as abandoned?

In the log below, I would like to respond to your statement that abandoned leases are not related to declined ones. While it may be a rule, in practice, on this particular version, you can see that the lease is declined, then marked abandoned, then reclaimed and immediately reused. Please correct me if I misunderstand, when you see "Abandoning IP address xx.xx.xx.xx :declined - this means the IP is marked abandoned?

During the time below, there were over 150 free leases:

> Apr 28 05:11:40 -dhcp-01 dhcpd: DHCPACK on 192.168.194.20 to 00:00:00:aa:bb:cc via 192.168.194.1

> Apr 28 05:11:41 -dhcp-01 dhcpd: Abandoning IP address 192.168.194.20: declined.

> Apr 28 05:11:41 -dhcp-01 dhcpd: DHCPDECLINE of 192.168.194.20 from 00:00:00:aa:bb:cc via 192.168.194.1: not found

> Apr 28 05:11:51 -dhcp-01 dhcpd: DHCPDISCOVER from 00:00:00:aa:bb:ccvia 192.168.194.1

> Apr 28 05:11:52 -dhcp-01 dhcpd: DHCPOFFER on 192.168.194.30 to 00:00:00:aa:bb:cc via 192.168.194.1

> Apr 28 05:11:52 -dhcp-01 dhcpd: DHCPREQUEST for 192.168.194.30 from 00:00:00:aa:bb:cc via 192.168.194.1

> Apr 28 05:11:52 -dhcp-01 dhcpd: DHCPACK on 192.168.194.30 to 00:00:00:aa:bb:cc via 192.168.194.1

> Apr 28 05:13:42 -dhcp-01 dhcpd: Reclaiming abandoned IP address 192.168.194.20.

> Apr 28 05:13:42 -dhcp-01 dhcpd: DHCPDISCOVER from 00:00:00:zz:yy:xx  via 192.168.194.1

> Apr 28 05:13:43 -dhcp-01 dhcpd: DHCPOFFER on 192.168.194.20 to 00:00:00:zz:yy:xx  via 192.168.194.1

> Apr 28 05:13:43 -dhcp-01 dhcpd: DHCPDISCOVER from 00:00:00:zz:yy:xx  via 192.168.194.1

> Apr 28 05:13:43 -dhcp-01 dhcpd: DHCPOFFER on 192.168.194.20 to 00:00:00:zz:yy:xx  via 192.168.194.1

> Apr 28 05:13:45 -dhcp-01 dhcpd: DHCPDISCOVER from 00:00:00:zz:yy:xx  via 192.168.194.1

+=---------------- --- -  . ---  .-+
 Jeffrey Stettenbenz
|Cinergy Metronet
 IP Operations and Engineering
|Network Technician
|812.253.1552
+=----------------------- --  -- - ---     -

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