Rejecting duplicate static IP addresses on core switch

[binsu158]

Good day everyone!

May I just ask for a solution for this problem. There was a time wherein an IP phone that had an incorrect IP address installed for a client. Apparently, the IP address that was supplied to the phone was already in use in the network as it was misconfigured by a third-party. As a result, it brought down our core switch resulting in a lengthy downtime. It experienced high CPU usage as well. Currently, we are implementing static IP addressing for our clients to easily identify them for troubleshooting purposes. 

Is there a possible way to reject duplicate static IP addresses on our core switch? An area that we already looked at is with ARP since we found out that the ARP process shot up when that problem occurred.

[Seb Rupik]

HI there,

A better solution would be to use DHCP for the phones, you could also configure IP reservation for each of them if required.

Combine this with DHCP snooping and Dynamic ARP Inspection at the access layer, it will reduce the possibility of duplicate IPs occurring on your network.

Cheers,

Seb.

[pieterh]

if you want, you can create an access list that block the offending ip-address incomming and apply this acl to client access ports.

but....

a duplicate ip-address should not "bring down" your core switch.

if this switch is the gateway for a certain subnet then yes, clients in this subnet may use the wrong device as gateway.

other subnets should keep functioning.

if you configured your switch management on a separate vlan/subnet, you can still manage the switch from there

there may be something wrong with the driver on the client,

on connection to the network this could detect the ip address is al ready in use, give a warning and shut-down the interface?(and your switch stays operational.)