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DHCP - Hardware types

Community Veteran
Posts: 14,345
Thanks: 685
Fixes: 10
Registered: 01-08-2007

DHCP - Hardware types

Hi

In a DHCP packet the client specifies the hardware type it is using at the 2nd byte of the packet.

As I understand it, 1 is supposed to be for ethernet (though the TCP/IP guide states this as being 10Mb it seems to apply to all ethernet). 6 is supposed to be for IEE 802 networks. As I understand it, Wifi should be classed as a IEE 802 network however whenever I test my dhcp server from my netbook using ipconfig /renew or /release or from my phone the servers is sent a value of 1 for ethernet.

 

Is this how it should be?

I need a new signature... i'm bored of the old one!
2 REPLIES
mikelahey
Aspiring Pro
Posts: 179
Thanks: 64
Fixes: 10
Registered: 24-11-2015

Re: DHCP - Hardware types

DHCP is defined by 2 RFCs - RFC2131 and RFC2132.

RFC2132 contains the part of the spec which specifies the hardware identifier. https://tools.ietf.org/rfc/rfc2132.txt

See section 9.14 in the RFC. The hardware identifier comes from the address resolution protocol (ARP) which was defined in Std2 in 1994. https://tools.ietf.org/html/std2. ARP provides IP address to physical address translation on an ethernet network.

The age of the standard means that 10 megabits is specified against hardware type 1 ethernet. This type has been continued to be used for 100 megabit and gigbit ethernet even though the description is out of date.

To answer the next questiion 802.11 defines the wireless protocol, however the wireless connection is encapsulating ethernet frames - hardware type 1. This is why the DHCP packets have a hardware type 1 in their header, because they are ethernet frames encapsulated in 802.11.

Community Veteran
Posts: 14,345
Thanks: 685
Fixes: 10
Registered: 01-08-2007

Re: DHCP - Hardware types

Thanks, for the clarification!

I need a new signature... i'm bored of the old one!