DHCP Snooping not enabled for all Vlan.

agilent runprojects · ‎01-20-2014

Hi

We have enabled dhcp snooping for all vlan configured on the switch, but only few vlan show up as operational. Please clarify.

Cisco IOS Software, Catalyst 4500 L3 Switch Software (cat4500e-IPBASEK9-M), Version 12.2(53)SG8, RELEASE

ip dhcp snooping vlan 30,100-119,300-349,400-449,600,700,710,996-997

Switch#sh ip dhcp snooping

Switch DHCP snooping is enabled

DHCP snooping is configured on following VLANs:

30,100-119,300-349,400-449,600,700,710,996-997

DHCP snooping is operational on following VLANs:

30,108,308,600,700,710,996-997

DHCP snooping is configured on the following L3 Interfaces:

Insertion of option 82 is disabled

circuit-id default format: vlan-mod-port

remote-id: 0026.9914.8a80 (MAC)

Option 82 on untrusted port is not allowed

Verification of hwaddr field is enabled

Verification of giaddr field is enabled

DHCP snooping trust/rate is configured on the following Interfaces:

Interface Trusted Allow option Rate limit (pps)

----------------------- ------- ------------ ----------------

TenGigabitEthernet5/1 yes yes unlimited

Custom circuit-ids:

TenGigabitEthernet5/2 yes yes unlimited

Custom circuit-ids:

Port-channel1 yes yes unlimited

Custom circuit-ids:

Jeff Van Houten · ‎01-20-2014

Is there an active port on that switch for the non-operational snooping Vlans?

Sent from Cisco Technical Support iPad App

devils_advocate · ‎01-21-2014

Initially I thought the same as Jeff in that you needed ports in the Vlans before they became operational for DHCP snooping but a quick test on a 3750x I have here disproved that.

The only way I could replicate your scenario was to enable DHCP snooping for non existant Vlans.

For example, enabling DHCP snooping for Vlans 10-20 would show:

Switch#sh ip dhcp snooping

Switch DHCP snooping is enabled

DHCP snooping is configured on following VLANs:

10-20

DHCP snooping is operational on following VLANs:

10-20

But ONLY if Vlans 10-20 existed as L2 vlans.

If I deleted Vlan 19, I see the following:

Switch#sh ip dhcp snooping

Switch DHCP snooping is enabled

DHCP snooping is configured on following VLANs:

10-20

DHCP snooping is operational on following VLANs:

10-18,20

I suspect you have enabled DHCP snooping for L2 Vlans which do not actually exist in the Vlan database on that switch??