Static leases

[Bob McDonald]

An automatic lease comes from an assigned range of addresses on a subnet after matching either the defined host statement to the client identifier or the hardware address. It's granted an infinite lease.

A Static lease is granted from an assigned address to client identifier or hardware address relationship. This is also granted an indefinite lease time.

Are the above statements correct?

Does the logic for a ping check get executed when processing requests for either of these lease types?

Thanks,

Bob

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[james crilly]

Bob, 

I have no issues with clients receiving an ipv6 from the server.   The only real issue i have is the isc-dhcp-server6 doesnt service doesnt start on OS boot.  I have to start the service manually (service -isc-dhcp-server6 start) for the server to issue addresses.  I'm looking for a solution to where this server will start on boot. 

Thanks, 

Mike

On Tuesday, July 19, 2016 11:42 AM, Bob McDonald <[hidden email]> wrote:

An automatic lease comes from an assigned range of addresses on a subnet after matching either the defined host statement to the client identifier or the hardware address. It's granted an infinite lease.

A Static lease is granted from an assigned address to client identifier or hardware address relationship. This is also granted an indefinite lease time.

Are the above statements correct?

Does the logic for a ping check get executed when processing requests for either of these lease types?

Thanks,

Bob

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[Graham Clinch]

Hi Bob,

> An automatic lease comes from an assigned range of addresses on a subnet
> after matching either the defined host statement to the client
> identifier or the hardware address. It's granted an infinite lease.

I'm not sure about the phrase 'automatic lease' - are you referring to
reserved leases through enabling the infinite-is-reserved configuration
option?

> A Static lease is granted from an assigned address to client identifier
> or hardware address relationship. This is also granted an indefinite
> lease time.
>
> Are the above statements correct?
>
> Does the logic for a ping check get executed when processing requests
> for either of these lease types?

 From a quick skim of server/dhcp.c (looking just above the call to
'icmp_echorequest'), it looks like pings are not sent for a static lease
(presumably because the server can't do anything in response - for
dynamic pools it can try allocating a different address).

Graham
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[Simon Hobson]

Graham Clinch <[hidden email]> wrote:

>> An automatic lease comes from an assigned range of addresses on a subnet
>> after matching either the defined host statement to the client
>> identifier or the hardware address. It's granted an infinite lease.
>
> I'm not sure about the phrase 'automatic lease' - are you referring to reserved leases through enabling the infinite-is-reserved configuration option?


Indeed, there seems to be an issue of terminology here. AIUI there are three types of lease :

Dynamic - allocated from a pool of addresses according to whatever policies/rules may be in place (eg "known" host, member of class, etc)
Reserved - Identical to the above, but flagged as reserved and so the address cannot be re-allocated to another client after expiry of the lease
Static - a fixed-address statement within a host declaration assigning a fixed static address.

A static lease doesn't go through the normal lease processes - so it's not recorded in the leases file, there's no "expiry" as far as the server is concerned. The server just gives out the lease and that's the end of it until the client comes back to renew. As a side effect, dynamic DNS updates don't happen with static leases - though there's an option which will put DNS entries in when the lease is issued, but no mechanism to remove them later.

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