Dhcp

Hi,

Regarding to the CCNP switch-official certification guide, all the client/server messages are broadcasts.

On my wireshark i can see that only DHCP discover and DHCP request are broadcasts, and the other two messages (DHCP offer & ACK) are unicasts....

Am i missing something here....?

DHCP.JPG

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Comments

Cyanic

You are right only the Discover and Request are broadcast.

The Discover contains the MAC addy of the client, so the DHCP server does not need to broadcast.

ZblaJhaNi

Hi,

Yes this is true for Layer 2...
I dont know, how the DHCP offer & DHCP ACK`s can be Layer 3 unicats....

Thanks for explanation

Cyanic

It does not really matter as the host is only interested in the layer 2 address. Since the Offer and Acks are destined to the requesting host's layer 2 address, it accepts them, and process them. Layer 3 is just for routing, virtual hosts, and other higher layer processing once the frame is accepted.

ZblaJhaNi

Thanks

ZblaJhaNi

one question left.
Is DHCP option 82 enabled only, when you configure dhcp snooping?

thanks

Cyanic

No, DHCP options are set by the host or by the relay, and they are options.

What is DHCP Option 82? | Slaptijack

In the case of DHCP snooping you can insert this option.