3com WX3000 Manuel D’Utilisation

 

3-4 

Table 3-1 Ways of handling a DHCP packet with Option 82 

Drop 

— 

Drop the packet. 

Keep 

— 

Forward the packet without changing Option 82. 

Neither of the two 
sub-options is 
configured 

Forward the packet after replacing the original Option 82 with 
the default content. 

The storage format of Option 82 content is the one specified with 
the dhcp-snooping information format command or the 
default HEX format if this command is not executed. 

Circuit ID 
sub-option is 
configured 

Forward the packet after replacing the circuit ID sub-option of 
the original Option 82 with the configured circuit ID sub-option in 
ASCII format. 

Replace 

Remote ID 
sub-option is 
configured 

Forward the packet after replacing the remote ID sub-option of 
the original Option 82 with the configured remote ID sub-option 
in ASCII format. 

 

When receiving a DHCP client’s request without Option 82, the DHCP snooping device will add the 

option field with the configured sub-option and then forward the packet. For details, see 

. 

Table 3-2 Ways of handling a DHCP packet without Option 82 

Neither of the two 
sub-options is configured. 

Forward the packet after adding Option 82 with the default contents.

The format of Option 82 is the one specified with the 
dhcp-snooping information format command or the default HEX 
format if this command is not executed. 

Circuit ID sub-option is 
configured. 

Forward the packet after adding Option 82 with the configured circuit 
ID sub-option in ASCII format. 

Remote ID sub-option is 
configured. 

Forward the packet after adding Option 82 with the configured 
remote ID sub-option in ASCII format. 

 

The circuit ID and remote ID sub-options in Option 82, which can be configured simultaneously or 

separately, are independent of each other in terms of configuration sequence. 

 

When the DHCP snooping device receives a DHCP response packet from the DHCP server, the DHCP 

snooping device will delete the Option 82 field, if contained, before forwarding the packet, or will directly 

forward the packet if the packet does not contain the Option 82 field. 

A denial-of-service (DoS) attack means an attempt of an attacker sending a large number of forged 

address requests with different source IP addresses to the server so that the network cannot work 

normally. The specific effects are as follows: