DHCP Snooping Operation
1. Configure DHCP server that is connected to DHCP Snooper through trusted port.
2. Request an IP address from the DHCP client connected through the un-trusted port.
3. DHCP client broadcast the DHCP DISCOVER message to the switch.
4. DHCP server responds to the DHCP DISCOVER message with DHCP offer message to the client.
5. Once the DHCP OFFER is received by the client, it sends an DHCP REQUEST to the server.
6. DHCP server validates the request from the client and sends DHCP ACK with the offered IP address to the client with the lease time.
7. DHCP Snooper creates an entry for the above operation into the binding table which includes the MAC address of the host, the leased IP address, the lease time, the binding type, and the VLAN number and interface information associated with the host.
8. DHCP Snooper clears the entry in the binding table once the client sends the DHCP RELEASE query.
Validation
The show running-config ip dhcp snooping command displays the DHCP snooping commands configured on the device in question
#show running-config ip dhcp snooping
!
!
ip dhcp snooping bridge 1
ip dhcp snooping vlan 2 bridge 1
interface xe1
ip dhcp snooping trust
!
The show ip dhcp snooping bridge 1 command displays the configured information about DHCP Snooping.
#show ip dhcp snooping bridge 1
Bridge Group : 1
DHCP snooping is : Enabled
DHCP snooping option82 is : Disabled
Verification of hwaddr field is : Disabled
Rate limit(pps) : 100
DHCP snooping is configured on following VLANs : 2
DHCP snooping is operational on following VLANs : 2
DHCP snooping IP Source Guard is configured on the following Interface
Interface Trusted
--------------- -------
xe2 Yes
The show ip dhcp snooping binding bridge 1 command displays the binding table entries associated with un-trusted interfaces.
#show ip dhcp snooping bridge 1
Bridge Group : 1
DHCP snooping is : Enabled
DHCP snooping option82 is : Disabled
Verification of hwaddr field is : Disabled
Rate limit(pps) : 100
DHCP snooping is configured on following VLANs : 2
DHCP snooping is operational on following VLANs : 2
DHCP snooping trust is configured on the following Interfaces
Interface Trusted
-------- -------
Xe1 Yes
DHCP snooping IP Source Guard is configured on the following Interfaces
Interface Source Guard
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Last modified date: 10/19/2023