DHCP Circuit ID - vIOS

[ChrisNewnham_]

I am not sure if this is a vIOS_l2 15.2 specific issue, but when using the command ip dhcp relay information option globally, I found it does insert Agent Remote ID (Option 82 sub-option 2) but does not insert the circuit ID.

I believe it is supposed to do both. Can anyone advise or compare with a physical switch? Thanks!

[MHM Cisco World]

under the interface ?
MHM

[ChrisNewnham_]

Nope

sw110(config)#int g0/0
sw110(config-if)#ip dh
sw110(config-if)#ip dhcp sn
sw110(config-if)#ip dhcp snooping in
sw110(config-if)#ip dhcp snooping information ?
option DHCP Snooping information option

sw110(config-if)#ip dhcp snooping information op
sw110(config-if)#ip dhcp snooping information option ?
allow-untrusted DHCP Snooping information option allow-untrusted

sw110(config-if)#ip dhcp snooping information option

[MHM Cisco World]

Under interface? 

[MHM Cisco World]

Can I see show dhcp snooping in l2 SW client directly connected 

MHM

[ChrisNewnham_]

I see the layer 2 switch is adding the circuit ID (also confirmed from packet capture)..

sw110#show ip dhcp snoop
Switch DHCP snooping is enabled
Switch DHCP gleaning is disabled
DHCP snooping is configured on following VLANs:
101-102
DHCP snooping is operational on following VLANs:
101-102
DHCP snooping is configured on the following L3 Interfaces:

Insertion of option 82 is enabled
circuit-id default format: vlan-mod-port
remote-id: 5000.000e.0000 (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)
----------------------- ------- ------------ ----------------
GigabitEthernet1/0 yes yes unlimited
Custom circuit-ids:
GigabitEthernet1/1 yes yes unlimited
Custom circuit-ids:
GigabitEthernet1/2 yes yes unlimited
Interface Trusted Allow option Rate limit (pps)
----------------------- ------- ------------ ----------------
Custom circuit-ids:
GigabitEthernet1/3 yes yes unlimited
Custom circuit-ids:
Port-channel11 yes yes unlimited
Custom circuit-ids:
Port-channel12 yes yes unlimited
Custom circuit-ids:

However the ask was to add it from the layer 3 switch. If I try running DHCP snooping on the layer 3 switch, it never works. I have to switch it off to get it to work (even if I disable it on the L2 switch).

*Feb 4 12:36:08.801: DHCP_SNOOPING: message type : DHCPDISCOVER DHCP ciaddr: 0.0.0.0, DHCP yiaddr: 0.0.0.0, DHCP siaddr: 0.0.0.0, DHCP giaddr: 0.0.0.0, DHCP chaddr: 0050.7966.6826
*Feb 4 12:36:08.802: DHCP_SNOOPING_SW: bridge packet get invalid mat entry: FFFF.FFFF.FFFF, packet is flooded to ingress VLAN: (101)

[MHM Cisco World]

So we are in correct way. 

For l3 switch not add op82 even if we not enable dhcp relay, İ will check. 

But later next week, sorry I am in business trip these days. 

Thanks 

MHM