Guideline to Implement DHCP Snooping

[ytlee80]

Hi All,

I am trying to implement DHCP Snooping in production network. I have gone through the documentations, but i cannot test as my company is small and does not have any spare.

I know we need to trust the actual DHCP port and trunk. Also enable the feature globally and on vlan while disabling option 82.

What I would like to ask is the initial behaviour of the clients connecting to the switches. Will enabling dhcp snoop causes outage for these existing user? None of the documentation mention what happen initially to user who is not in the dhcp binding table, will their packet get drop? If they do, what is the best way to implement this feature?

Many thanks in advance.

BR

Michael

[Dan-Ciprian Cicioiu]

Hello Michael,

activating the dhcp snooping wouldn't cause any outage.
In my opinion you must set first the "ip dhcp snooping trust" on the interfaces that you will receive the traffic from DHCP server.
Then enable dhcp snooping globaly. (dhcp snooping vlans , disable option 82 , enable dhcp )

DHCP snooping is controlling the DHCP offers ( the packets that are coming from the server to the clients).
When you enable the dhcp snooping the clients with alocated IPs will have them until the lease time expires.

You can try after enabling DHCP snooping , renewing one of the PC's IP to cheack if everything is ok , and also check the switch "show ip dhcp snooping bindings"

HTH
Dan