Cisco DHCP Snooping Relay Setup Information

Switch#show ip dhcp snooping

Switch DHCP snooping is disabled DHCP snooping is configured on following VLANs: 1 Insertion of option 82 is enabled circuit-id format: vlan-mod-port remote-id format: MAC Option 82 on untrusted port is not allowed Verification of hwaddr field is enabled Interface Trusted Rate limit (pps) ------------------------ ------- ---------------- FastEthernet0/1 yes unlimited GigabitEthernet0/1 yes unlimited

To enable global "Switch DHCP Snooping":

Switch(config)#ip dhcp snooping

To enable DHCP snoop debugging

Note this only works IF the global dhcp snooping is enabled

debug ip dhcp snooping packet

To disable the DHCP debugging:

no debug ip dhcp snooping packet

Enable Port As Trusted:

You cannot broadcast DHCP unless the port is trusted so here's how you enable trust on a port (it does not work on a vlan I suppose for security reasons):

Switch(config-if)#int fa0/1 Switch(config-if)#ip dhcp snooping trust

Enable Snooping on VLAN:

Switch(config)# Switch(config)#ip dhcp snooping vlan 1

Allow Untrusted Port:

int fa0/3

ip dhcp snooping information option allow-untrusted

Disable Option 82

If the relay or destination DHCP server doesn't support Option 82 Information it will break your DHCP and you will NOT get an IP/lease.

So disable Option 82 unless you are sure your network supports it:

Switch(config)#no ip dhcp snooping information option

Resources:

https://community.cisco.com/t5/switching/dhcp-snooping-not-working-dropping-packets/td-p/2076543