Implementing DHCP Snooping

[ruben.montes]

Hello,

I'm going to implement DHCP snooping in a C4006 in a production environment. Is it a disruptive configuration? What would happen with all the IP addresses that were assigned prior to the configuration of snooping?

Any advise would be appreciated,

Ruben

[thisisshanky]

When you configure snooping, you tell which interfaces are trusted and which are untrusted. DHCP will be affected only to the untrusted interfaces. If there is a vlan that routes traffic to the Internet, that would be a good example of a untrusted interface.

But the default snooping trust value is "Untrusted". So when you configure your inside vlan with snooping, the interface is first set to Untrusted until you enter the command to change it to Trusted.

I am not sure if it purges the DHCP bindings when snooping is configured, but definitely new DHCP requests will be blocked until you configure it as a trusted interface. Even if the bindings are purged, I would think, as long as the client (PC) does not reboot its IP address will be still intact.