DHCP server problem

Hey,

Working on a lab and came across problem with dhcp and I am not sure why
it's not working. Scenario asks to config R3 as DHCP server, the dhcp client
is a switchport one hop away. I was able to setup the pool and the links
correctly, but the switchport never get the address. Debugging did not
provide any glaring answers. Can someone shed light on this.

R3 fa0/0 ======FA0/1-SW2-FA0/21=======FA0/21-SW3

R3
DHCP server R3
Pool 172.16.90.0/24

SW2
L3 link between R3 fa0/0 and SW2 fa0/1
SVI VLAN 90 on SW2
ip helper on SVI 90 pointing toward R3 fa0/0

VLAN 90 between SW2 fa0/21 and SW3 fa0/21

SW3
SW3 fa0/21 ip address dhcp

R3
!
ip dhcp pool VLAN90
default-router 172.16.90.1
network 172.16.90.0/24
lease infinite

interface fa0/0
ip address 172.16.31.3/24

SW2

ip dhcp snooping
ip dhcp snooping vlan90

int fa0/1
ip address 172.16.31.20/24

int fa0/21
switchport mode access
switchport access vlan 90

interface vlan 90
ip address 172.16.90.21/24
ip helper-address 172.16.31.3

SW3
interface fa0/21
switchport mode access
switchport access vlan 90

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Received on Sat Apr 23 2011 - 16:12:30 ART