ip dhcp snooping...what happens when cisco 3750 is dhcp server?

murray-davis · ‎11-24-2008

I want to implement dhcp snooping on a LAN for vlan 2. On this LAN, one 3750 is in ip routing mode and is configured as a dhcp server for clients on vlan2. I understand how to implement dhcp snooping on 2960 swithes so that their uplink ports trust the connection to this 3750, but how do I configure the 3750? Do I need to configure this switch, since it would need to effectively trust itself?

Mark Yeates · ‎11-24-2008

Murray,

I would still apply DHCP snooping on the VLAN interface on the 3750. Although it is still local to the switch there is still the possibility.... It's better to be safe then sorry.

HTH,

Mark

murray-davis · ‎11-24-2008

Thank you, Mark. If I understand correctly, here is how I would configure the 3750:

ip dhcp snooping vlan 2

int vlan 2

ip dhcp snooping trust

no ip dhcp snooping information option

ip dhcp snooping

NOTE: Here is how I have dhcp configured on this 3750 switch for vlan 2 which has been working fine for about 2 years.

ip dhcp excluded-address 172.16.0.1 172.16.2.0

!

ip dhcp pool Clients

network 172.16.0.0 255.255.0.0

default-router 172.16.1.10

dns-server 204.174.64.1 204.174.65.1

interface Vlan2

ip address 172.16.1.10 255.255.0.0

Mark Yeates · ‎11-24-2008

That should work just fine.

Mark