Cisco – logging dhcp leases to syslog server on cisco router

You almost got it working ,

In your staticmap file just change the Type of '1' to : 'id' ,

static file :

*time* Sep 3 2012 11:10 AM
*version* 1
!IP address    Type    Hardware address     Lease expiration
10.0.0.8 /8     id       0100.301b.473d.d8       Infinite
10.0.0.28 /8    id       0184.8f69.b77b.dc       Infinite
*end*

And the config snippet :

!
ip dhcp pool StaticBindings
 origin file flash:static-bindings
 default-router 10.0.0.1
 dns-server 10.0.0.1
 netbios-name-server 10.0.0.1
! 

Works like a charm. ( Cisco 3945E )

DCHP lease are client based. It's the client that request lease, ask later if it can renew it (to extend it and so keep the ip).

While the lease is valid, clients keep their config. But they will contact again the dhcp server before the end to try to renew it.

So you could have a dhcp lease big enough to handle the change. Take care, removing the router will make client unable to reach what was behing the router (internet for example), while the new one is not ready.

If the new router provide ip using another subnet, client will use this new subnet when their current lease expire. To handle the change, your router must have ip in both new and old (2 ip on same ethernet card), and provide lease only on the new one. So old client still works, and new one too.

You could do a batch using psexec for example to connect remotely on each computer and do an ipconfig /renew to force the change before lease expire.