From: Scott Morris (swm@emanon.com)
Date: Tue May 17 2005 - 10:59:59 GMT-3
UDP port 0 is used as a source port for many different things. Some refer
to it as the "unknown" port. Others as the "base" port.
IANA and other places list it simply as "reserved"
It really all boils down to what programmers use it for. It has roots back
in the unix days for dynamic stuff.
It's hard to find any good web reference about it, but I dug this up for
you:
http://compnetworking.about.com/od/tcpip/l/blports_0.htm
Cheers,
Scott
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
eward15@juno.com
Sent: Tuesday, May 17, 2005 9:53 AM
To: swm@emanon.com
Cc: eward15@juno.com; ccielab@groupstudy.com
Subject: RE: DLSW UDP ports
Scott,
Thanks for your help. I labbed it last night and saw the UDP port 2067
traffic. Very interesting. The two routers tried to negotiate capabilities
with DLSw version 1. Once they saw each other as being Cisco peers, the
higher address dropped the connection (RST flag set). Then they went to
version 2, with 30 sec keepalives on TCP port 2065. That part was expected.
However, when I tried to establish a circuit end-to-end, I saw that the
source DLSw router was sourcing from UDP port 0 to the destination UDP port
2067. UDP port 0...?
Eugene Ward
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The UDP stuff is for non-critical traffic, such as "canureach"
and things
like that...
HTH,
Scott
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
eward15@juno.com
Sent: Monday, May 16, 2005 3:23 PM
To: ccielab@groupstudy.com
Subject: DLSW UDP ports
I was doing a packet capture between two routers to compare DLSw ports. I
was searching the archives when I ran across this post from Scott Morris:
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Well... Those aren't exactly helpful as they are the original RFC
implementation of DLSW. But a good idea to look there anyway!
Access-list 100 deny tcp any range 11000 11999 any eq 2065 (incoming)
Access-list 100 deny tcp any eq 2065 any range 11000 11999 (outgoing)
Access-list 100 deny udp any eq 0 any eq 2067 (incoming) Access-list 100
deny udp any eq 2067 any eq 0 (outgoing) Access-list 100 permit ip any any
The original way was from 2067 to 2065 both ways.
Scott
-----------------------------------------------------------------------
I was able to see the tcp ports and the tcp keepalives; however, I didn't
get a chance to establish a ciruit between two computers. Can I assume that
the UDP ports are for explorer traffic? (I will lab this up when I get a
chance.)
Eugene Ward
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