Why do we need ip dhcp relay information trusted command?

--> When we enable ip dhcp snooping on the switch, it will insert option 82 information to provide additional information about the client to the server.

--> As well as switches will make giaddress as 0.0.0.0

--> The problem with this is, whenever the router which is acting as DHCP server or DHCP Relay agent receives any DHCP message with giaddress value 0.0.0.0 it simply drops the packet.

--> In order to prevent this either dont insert option 82 information on the switch by using the following command ( no ip dhcp snooping information option ) .

--> If you want to allow the dhcp packets with giaddress 0.0.0.0 on DHCP server or Relay Agent simply configure following command

int e0/0

ip helper-address 10.1.1.1

ip dhcp relay information trusted.