From: Jian Gu (guxiaojian@gmail.com)
Date: Wed Dec 20 2006 - 17:45:57 ART
Do you have ip dhcp snooping option turned-on on switch2? by defaut switch1
will drop all DHCP packets with option82 inserted, use the following command
to allow DHCP packets to go through.
*"ip dhcp snooping information option allow-untrusted"*
Anyway, it is just my guess, "debuging ip dhcp snooping" on both
switch1 and switch2 should tell you where the
problem is, it is a simple feature.
On 12/20/06, dampened <cheechew@hotmail.com> wrote:
>
> I have topology where there are 2 switches, upstream and downstream. The
> DHCP server is on vlan 2 and client on vlan 3. Both switch are connected
> by
> trunk.
> Here is the skeleton of the config.
>
> When ip put "ip dhcp snooping vlan 3" on switch 2, the client could not
> get
> IP from DHCP. When I removed it, everything is fine, the binding is
> properly
> built on switch 1. But without the snooping on switch 2, the feature
> actually is not yet configured. Whats wrong with my config?
>
>
>
>
> switch-1:
>
> ip dhcp snooping
> ip dhcp snooping vlan 3
>
> interface f0/1
> description connect to DHCP server
> switchport access vlan 2
> switchport mode access
> ip dhcp snooping trust
>
> interface f0/24
> description trunk to switch 2
>
> interface vlan 2
> ip address ...
>
> interface vlan 3
> ip address ...
> ip helper-address dhcp_server
>
>
>
> switch-2:
>
> ip dhcp snooping
> ip dhcp snooping vlan 3 <-----------------------------
>
> interface f0/1
> description connect to DHCP client
> switchport access vlan 3
> switchport mode access
>
> interface f0/24
> description trunk to switch 1
> ip dhcp snooping trust
>
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