DHCP Snooping on a trunk interface

[Rodrigo Gurriti]

Hello

I have the following set up on my network.

My problem is that i cannot get a DHCP address on the client.

I have the following config for both:

Global

#################################

ip dhcp snooping

ip dhcp snooping vlan 10 , 20 , 30

##################################

Interface trunk

#################################

switchport mode trunk

switchport trunk allow vlan 10,20,30

switchport trunk encapsulation dot1q

ip dhcp snooping trurst *only on the Client's switch

#################################

Thank you !

[Ganesh Hariharan]

My problem is that i cannot get a DHCP address on the client.
I have the following config for both:
Global
#################################
ip dhcp snooping
ip dhcp snooping vlan 10 , 20 , 30
##################################
Interface trunk
#################################
switchport mode trunk
switchport trunk allow vlan 10,20,30
switchport trunk encapsulation dot1q
ip dhcp snooping trurst *only on the Client's switch
#################################
Thank you !

Hi,

To configure DHCP snooping just follow these steps

The first step to configure DHCP Snooping is to turn on DHCP snooping in all Cisco Switches using the “ip dhcp snooping” command.

All Cisco Switches (config)#ip dhcp snooping

Second step is to configure the trusted interfaces,

Switch(config)#interface range  gigabitEthernet 3/21 - 23
Switch (config-if)#ip dhcp snooping trust

Finally configure VLANS for DHCP snooping DHCP snooping will used on all the VLANs

Hope to Help !!

Ganesh.H

[Rodrigo Gurriti]

I've got working but only when i add the comand ip dhcp snooping trust to both trunking interfaces.... why is that ? should not it only need the trust command on the client's switch trunk ? Why does it need to be on both trunks? The servers switch only will forwared the DHCP packets to the client why does it need to be trusted ?

Thank you !

[July sall]

this explain quite well, mostly due to option82 enabled by default.

http://packetpushers.net/ccnp-studies-configuring-dhcp-snooping/