DHCP snooping on a cascaded network configuration example

As shown in Figure 39, multiple DHCP snooping devices exist on a cascaded network.

Enable the ports connected to the DHCP server and other DHCP snooping devices to forward DHCP server responses.

To save system resources, disable the ports indirectly connected to the DHCP clients from recording clients' IP-to-MAC bindings.

1. Configure Switch A:

   # Enable DHCP snooping.

   <SwitchA> system-view
   [SwitchA] dhcp-snooping
   

   # Configure GigabitEthernet 1/0/2 as a trusted port.

   [SwitchA] interface GigabitEthernet 1/0/2
   [SwitchA-GigabitEthernet1/0/2] dhcp-snooping trust
   [SwitchA-GigabitEthernet1/0/2] quit
   

   # Disable the untrusted port GigabitEthernet 1/0/3 from recording clients' IP-to-MAC bindings.

   [SwitchA] interface GigabitEthernet 1/0/3
   [SwitchA-GigabitEthernet1/0/3] dhcp-snooping no-user-binding
   [SwitchA-GigabitEthernet1/0/3] quit
   

2. Configure Switch B:

   # Enable DHCP snooping.

   <SwitchB> system-view
   [SwitchB] dhcp-snooping
   

   # Disable the untrusted port GigabitEthernet 1/0/1 from recording clients' IP-to-MAC bindings.

   [SwitchB] interface GigabitEthernet 1/0/1
   [SwitchB-GigabitEthernet1/0/1] dhcp-snooping no-user-binding
   [SwitchB-GigabitEthernet1/0/1] quit
   

   # Configure GigabitEthernet 1/0/2 as a trusted port.

   [SwitchB] interface GigabitEthernet 1/0/2
   [SwitchB-GigabitEthernet1/0/2] dhcp-snooping trust
   [SwitchB-GigabitEthernet1/0/2] quit
   

3. Configure Switch C:

   # Enable DHCP snooping.

   <SwitchC> system-view
   [SwitchC] dhcp-snooping
   

   # Configure GigabitEthernet 1/0/2 as a trusted port.

   [SwitchC] interface GigabitEthernet 1/0/2
   [SwitchC-GigabitEthernet1/0/2] dhcp-snooping trust
   [SwitchC-GigabitEthernet1/0/2] quit
   

   # Disable the untrusted port GigabitEthernet 1/0/3 from recording clients' IP-to-MAC bindings.

   [SwitchC] interface GigabitEthernet 1/0/3
   [SwitchC-GigabitEthernet1/0/3] dhcp-snooping no-user-binding
   [SwitchC-GigabitEthernet1/0/3] quit
   

   # Disable the untrusted port GigabitEthernet 1/0/4 from recording clients' IP-to-MAC bindings.

   [SwitchC] interface GigabitEthernet 1/0/4
   [SwitchC-GigabitEthernet1/0/4] dhcp-snooping no-user-binding
   [SwitchC-GigabitEthernet1/0/4] quit