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New Member


I have DHCP configured on a 2600 router. When I do show IP address binding, I see list of IP addresses bind to many MAC addresses. However, they are actually NOT active, because they are not replying when I ping them. Because of that, the DHCP scope is running out of IP addresses to release to workstations. When I clear the binding, the DHCP will start to release IP address again. When IP address not active (not replying by pinging them), those IP addresses should go back to the pool immediately. Please advice.



By default the lease time for Cisco IOS dhcp server is 1 day. If a workstation got an ip address, and if the workstation is not on, for more than a day, is the ip address, leased to the workstation, still remain in the binding ????

You can try reducing the lease time, so that you can free up the bindings in the database faster.

New Member


If I understand you right, you probably don't have enough IP addresses for your workstations. The DHCP server ( router, in this case) is handing out IP address but when workstations disconnect or are no longer active, they are not releasing their IP address.

This is because of the lease time for an IP address by default the lease time is 1 day. So even after the machine disconnects it still has a lease on that IP address for 1 day. So you either have to up the ammount of IP's in your DHCP pool, or decrease the lease time.

You should find this link Helpful.

New Member


Another Note

If you decrease the lease time, let's say to something crazy like 10 minutes, you will increase the DHCP traffic on your network, as well as create more load for your router. This may not be an issue for you, but please keep it in mind if you start to experience network slow down.

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