DHCP Ports - Clarification

[Gerald Combs]

On Fri, 9 Aug 2002, jose sanchez wrote:

> Can someone please tell me what ports does dhcpcd
> program uses to communicate with a dhcp server. And
> what port does the dhcp server runs on. 
> 
> I thought that a dhcp server runs on port 67 and the
> client on port 68.

That's correct.  

> I am using dhcpcd on a RH 7.2 system. I revised the
> /etc/services file for port 67 and 68 and this is
> what's in there:
> bootps          67/tcp           # BOOTP server
> bootps          67/udp
> bootpc          68/tcp           # BOOTP client
> bootpc          68/udp

That's correct.

> I also cat /etc/services | grep dhcp and this is what
> I got:
> dhcpv6-client   546/tcp
> dhcpv6-client   546/udp
> dhcpv6-server   547/tcp
> dhcpv6-server   547/udp
> 
> Looks like that's for IP v6.

That's correct.

> Is bootp and dhcpcd the same and would use the same
> ports?

DHCP is an extension/update of BOOTP.  It adds lease times and more room
for options/vendor extensions.  Both protocols use the same ports, and the
packet formats are fairly similar.  The services file entries are still
named "bootps" and "bootpc" on most Unix/Linux systems, but the actual
client and server software uses DHCP nowadays.

Comparisons of BOOTP and DHCP can be found at:

  http://www.networksorcery.com/enp/protocol/dhcp.htm

  http://www.cisco.com/warp/public/779/smbiz/service/knowledge/tcpip/dhcp.htm

  
http://www.microsoft.com/windows2000/en/server/help/default.asp?url=/windows2000/en/server/help/sag_
DHCP_und_Bootp.htm

There are a bunch of RFCs relating to BOOTP and DHCP: 

  RFC  951: Bootstrap Protocol
  RFC 1497: BOOTP extensions
  RFC 1542: Clarifications and Extensions for the Bootstrap Protocol
  RFC 2131: Dynamic Host Configuration Protocol
  RFC 2132: DHCP Options and BOOTP Vendor Extensions
  RFC 2489: Procedure for Defining New DHCP Options
  RFC 3046: DHCP Relay Agent Information Option
  RFC 3118: Authentication for DHCP Messages

IANA maintains the official list of options and vendor extensions at
 
  http://www.iana.org/assignments/bootp-dhcp-parameters

> Please help.
> 
> Thanks in advance for your help.

Sorry for the information overload.  I just happened to have it on hand.

> 
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