DHCP Lammle vs Odom?

showbo

Hey guys, testing out on ICND1 on Sept. 28th. Got done reading Lammle, now power reading Odom. Got to DHCP with Odom and went .......

Lammle shows the four step process as: Client Broadcast DHCPDiscover>Server Unicast DHCPOffer>Client Broadcast DHCPRequest>Server Unicast DHCPACK.

Odom: DHCP Discover (Broadcast)>DHCP Offer (Broadcast)>DHCP Request directed at server>DHCP Ack directed to client.


Awesome. I already got Lammle's way in my head. Who is right, or more right here?

TurK-FX

I am about 500pages down on Odom ICND1 and as far as i remember, he says same thing Lamme says.
Cliend DHCP discover message - DHCP server offer - client accepts to first offer - DHCP sends the rest of the info cliend needs.

sizeon

Lammle is right. Offer and acknowledgment are unicast

showbo

sizeon wrote: »

Lammle is right. Offer and acknowledgment are unicast

Good, that is what I got myself to learn and know. Thanks sizeon.

mapletune

DHCP (Dynamic Host Configuration Protocol) Basics

from Microsoft.

Understanding and Troubleshooting DHCP in Catalyst Switch or Enterprise Networks - Cisco Systems

from Cisco.

In a nutshell, all packets in a simple, 1 subnet network, will be broadcasts with client mac address information inside so that the client knows this broadcast is for the client.

However, in a more complex network where DHCP forwards occur, then refer to the following:

The DHCP server will send the DHCPOFFER to the broadcast address, but will include the clients hardware address in the chaddr field of the offer, so the client knows that it is the intended destination. In the event that the DHCP server is not on the local subnet, the DHCP server will send the DHCPOFFER, as a unicast packet, on UDP port 67, back to the DHCP/BootP Relay Agent from which the DHCPDISCOVER came. The DHCP/BootP Relay Agent will then either broadcast or unicast the DHCPOFFER on the local subnet on UDP port 68, depending on the Broadcast flag set by the Bootp client.

Hope that helps,
Mike