HP 6125G HP 6125G & 6125G/XG Blade Switches Layer 3 - IP Services Conf - Page 57

Application environment of trusted ports, Configuring a trusted port connected to a DHCP server

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including IP addresses, MAC addresses, and CVLANs, before sending the packets to clients. For more information, see Layer 2-LAN Switching Configuration Guide. Application environment of trusted ports Configuring a trusted port connected to a DHCP server As shown in Figure 32, the DHCP snooping device port that is connected to an authorized DHCP server should be configured as a trusted port. The trusted port forwards reply messages from the authorized DHCP server to the client, but the untrusted port does not forward reply messages from the unauthorized DHCP server. This ensures that the DHCP client obtains an IP address from the authorized DHCP server. Figure 32 Configuring trusted and untrusted ports DHCP server Trusted DHCP snooping Untrusted Untrusted DHCP client Unauthorized DHCP server DHCP reply messages Configuring trusted ports in a cascaded network In a cascaded network involving multiple DHCP snooping devices, the ports connected to other DHCP snooping devices should be configured as trusted ports. To save system resources, you can disable the trusted ports, which are indirectly connected to DHCP clients, from recording client IP-to-MAC bindings upon receiving DHCP requests. 49

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49
including IP addresses, MAC addresses, and CVLANs, before sending the packets to clients. For
more information, see
Layer 2
—
LAN Switching Configuration Guide
.
Application environment of trusted ports
Configuring a trusted port connected to a DHCP server
As shown in
Figure 32
, the DHCP snooping device port that is connected to an authorized DHCP server
should be configured as a trusted port. The trusted port forwards reply messages from the authorized
DHCP server to the client, but the untrusted port does not forward reply messages from the unauthorized
DHCP server. This ensures that the DHCP client obtains an IP address from the authorized DHCP server.
Figure 32
Configuring trusted and untrusted ports
Configuring trusted ports in a cascaded network
In a cascaded network involving multiple DHCP snooping devices, the ports connected to other DHCP
snooping devices should be configured as trusted ports.
To save system resources, you can disable the trusted ports, which are indirectly connected to DHCP
clients, from recording client IP-to-MAC bindings upon receiving DHCP requests.
Trusted
DHCP server
DHCP snooping
Untrusted
Untrusted
Unauthorized
DHCP server
DHCP client
DHCP reply messages