Enabling DHCP snooping

Andy White · ‎03-19-2015

Hello,

We have a 2960 48 port switch in a remote office with a couple of VLANs (VOIP & Data). The L3 routing is provided via the WAN router and acts as a 'router on a stick' and provides DHCP for both VLANs.

I need to enable DHCP snooping and I have issued the 'ip dhcp snooping trust' on the router port but not for the access ports. I have then added 'ip dhcp snooping' to the switch but not 'ip dhcp snooping vlan x , x' as I was hoping the ip dhcp snooping bindings database would start to fill up after a few days but it hasn't.

If I add 'ip dhcp snooping vlan x , x' I think the users will get issues as there is no database, what should I do as the router is doing the DHCP.

Thanks

petenixon · ‎03-19-2015

You need to identify the vlans where snooping should be implemented using:

ip dhcp snooping vlan #

The default allows dhcp requests on untrusted ports.

Andy White · ‎03-19-2015

That's my question, if I enable it on the vlans and the database isn't populating, what will happen?

petenixon · ‎03-19-2015

DHCP snooping keeps track of the bindings but you first have to identify what vlans need tracking.

Andy White · ‎03-19-2015

Thanks, but what will happen if I enable this and the database isn't populated yet?