H3C Technologies H3C S5120 Series Switches - Manual (Page 256)

3-3
Figure 3-2 Configure trusted ports in a cascaded network
Table 3-1 describes roles of the ports shown in Figure 3-2 .
Table 3-1 Roles of ports
Device Untrusted port
Trusted port disabled from
recording binding entries
Trusted port enabled to
record binding entries
Switch A GigabitEthernet 1/0/1 GigabitEthernet 1/0/3 GigabitEthernet 1/0/2
Switch B
GigabitEthernet 1/0/3
and GigabitEthernett
1/0/4
GigabitEthernet 1/0/1 GigabitEthernet 1/0/2
Switch C GigabitEthernet 1/0/1
GigabitEthernet 1/0/3 and
GigabitEthernet1/0/4
GigabitEthernet 1/0/2
DHCP Snooping Support for Option 82
Option 82 records the location information of the DHCP client. The administrator can locate the DHCP
client to further implement security control and accounting.
If DHCP snooping supports Option 82, it will handle a client’s request according to the contents defined
in Option 82, if any. The handling strategies are described in the table below.
If a reply returned by the DHCP server contains Option 82, the DHCP snooping device will remove the
Option 82 before forwarding the reply to the client. If the reply contains no Option 82, the DHCP
snooping device forwards it directly.
If a client’s
requesting
message has…
Handling
strategy
Padding
format
The DHCP snooping device will…
Drop Random Drop the message. Option 82
Keep Random
Forward the message without changing
Option 82.