DHCP option 82
I know there are some posts in the forum regarding the issue but I still have some questions regarding this matter after reading the other posts
After reading Petr post regarding this issue I still have a couple of questions, mainly regarding the following sentences:
"Notice that by default Cisco IOS devices reject packets with zero “giaddr” and by default Cisco Catalyst switches use “giaddr” of zero when configured for DHCP snooping!"
"By default, when you enable DHCP snooping in a 3550/3560 switch, the switch will be inserting the information option but will set “giaddr” to zero. To handle this in an IOS router, use the command ip dhcp relay information trust-all to accept packets with zero “giaddr”."
1. Cisco IOS routers configured has relay agents (not has DHCP server) will drop DHCP packets (DHCPDISCOVER, DHCPREQUEST) that entered through a switch configured with "dhcp snooping" (by default the 3550/3560 attach option 82 when configured for DHCP snooping) because the packet arrived at the relay agent with a giaddr=0.0.0.0 plus the OPTION 82 (both attached by the switch)......is this assumption correct ?
2. A normal DHCP client connected to a switch not implementing DHCP Snooping (so no option 82 attached by the switch), will have giaddr=0.0.0.0 but since it arrives at the relay agent without the option 82 attached it will be relayed