{DANGEROUS?} SV: Option 82 fast change

Marc Perea marccp at srttel.com
Fri Sep 12 13:25:45 UTC 2008


Hi again. Yes, we can depend on the remote equipment to set the option82.circuit-ID ALWAYS the same. Our implementation includes a DSLAM double Vlan tagging and inserting L2 option 82 info. Our circuit-ID in the DHCP packet is not allowed for the client to set, it happens at the DSLAM.

Thank you for the recommendation of ending the leasetime early with omapi, I tried removing a lease but not adjusting the timing - I'll give that a shot.



	Be careful what you wish for.
	Over-riding leases is likely to be a source of problems.

	Can you depend on the customer to set the Client ID of the
	equipment to a site-specific string chosen by you?  This may
	be an immediate work-around, as the ISC DHCP server (IIUC)
	heeds a Client-ID string in preference to a MAC Address.

	IIRC, there has been some discussion on this list about the
	desirability of a configuration option to force the MAC address
	(rather than the Client ID string) to be the key for the lease.
	If this idea reaches the top of the work-list, it might be
	useful to consider providing an additional flavour of this
	option which would allow the lease key to be derived from
	Option-82 data.

	Best regards,

	Niall O'Reilly
	University College Dublin IT Services

------------------------------

Date: Thu, 11 Sep 2008 19:01:48 +0200
From: Christof Chen <christof at chen.de>
Subject: Re: {DANGEROUS?} SV: Option 82 fast change

Anders Rosendal schrieb:
>
> Have a public network where customers are assigned one "static ip" through dhcp, and when they change equipment on there ports they don't get the IP for the "new" equipment. 
> Would like to see some kind of leasetime-override.
>  

You can override the lease-end time with omapi.

This isn't as nice as using the switchport id as an client-identifier,
but way easier than stopping dhcpd, editing the lease file and
restarting the daemon.

Christof Chen


Marc Perea
Network Support Engineer
SRT Communications, Inc.





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