Block Cisco Router 881 for assigning a particular IP Address

[VikramRomana6443]

Hello Cisco team,

I have a Cisco 881 Router and it is assigning an IP: 10.64.36.116 to a Cisco IP Phone. I dont want this IP to be assigned to be any device. I have written a command on the Router: ip dhcp excluded-address 10.64.36.116 but still the Router is assigning the same IP to the IP Phone. I have restarted the phone after typing the above command on the Router but it still got the same IP. Is this command correct or does it need to be corrected ?

Please advise accordingly at the earliest.

Thanks,

Vik.

[Seb Rupik]

Hi there,

Assuming the 881 is the DHCP server managing the scope for the subnet that 10.64.36.116 resides in, then yes, the ip dhcp exclude command is the correct one to use.

Does the IP address show up in the binding table?

sh ip dhcp server bind

...can you try and clear the binding:

clear ip dhcp binding 10.64.36.116

Now restart the phones network interface and see if it picks up the same address.

cheers,

Seb.

[VikramRomana6443]

ok thanks for the update.

[Georg Pauwen]

Hello,

you could also create a static client reservation bound to a non-existing MAC address, to make sure the IP address never gets assigned. Below are the reservations (both client-id and hardware address, you might want to configure both):

ip dhcp pool BLACKHOLE_IP_PHONE_1
host 10.64.36.116 255.255.255.0
client-identifier 0100.333c.444d.5f
!
ip dhcp pool BLACKHOLE_IP_PHONE_2
host 10.64.36.116 255.255.255.0
hardware-address 0033.3c44.4d5f

[VikramRomana6443]

Ok thanks for the update.