IP DHCP Snooping

[Andrew White]

Hello,

i have enabeld DHCP snooping on a switch:

ip dhcp snooping vlan 10

ip dhcp snooping

Then plugged in a Cisco router (fa 0/2) that has a DHCP scope and then did an "ipconfig /release" then "ipconfig /renew" and the laptop doesn't get an IP, great.

However the table shows nothing, should I see fa 0/2 as trusted = no?

Switch#sh ip dhcp snooping

Switch DHCP snooping is enabled

DHCP snooping is configured on following VLANs:

10

DHCP snooping is operational on following VLANs:

10

DHCP snooping is configured on the following L3 Interfaces:

Insertion of option 82 is enabled

   circuit-id default format: vlan-mod-port

   remote-id: 0022.0db8.2c00 (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)

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

Switch#

Thanks

[cadet alain]

Hi,

However the table shows nothing, should I see fa 0/2 as trusted = no?

No, by dfefault all ports are untrusted and you should put the uplink interfaces to valid DHCP server as trusted with the interface command ip dhcp snooping trust

Regards

Alain

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[Andrew White]

How can I find out if a rougue DHCP server is ever installed?