Option 82 & limit lease 1

Marc Perea marccp at srttel.com
Thu Apr 22 21:37:33 UTC 2010

>From: Scott Baker <scott at perturb.org>
>Subject: Re: Option 82 & limit lease 1
>I think maybe I missed part of the conversation. What's "option matching"?

Option matching appears to be a new feature in 4.2.x. It allows you to define a host by an option, instead of (in addition to?) by a mac-address. For a service provider, like us, this is a HUGE step forward (thanks btw to ISC for adding this feature). We've seen improvement of 2 orders of magnitude in performance over our old configuration on 3.1.2 both in restart times of the daemon and in DORA/second.
As example, we used to define a class that matched on a specific option 82 (agent.circuit-id). Then we'd build a pool. Then we'd build a range (of 1 IP). Then apply the filter of our class to the range. For tens of thousands of customers, that's a very large conf file. And it's slow, _really_ slow.
With 4.2, one can define a host and give it a fixed address. Done. It's very, _very_ nice. Smokin' performance too.
And because I couldn't find it documented anywhere (man pages referred to ipv6, but this works in ipv4 too), it goes like:
host [some_unique_host_name] { host-identifier option agent.circuit-id "[some_static_CID]"; fixed-address [a.b.c.d]; } #[some_customer_identifier]
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