UDP port 137 Question
ekgermann at cctec.com
Wed Jan 7 15:26:01 UTC 1998
One interesting thing MS does is an extension of the resolver libraries.
For example, if I do a netstat -a to show all the connections on my server,
it will try and resolve the IP back to a name (reverse lookup via
in-addr.arpa). However, the extension is: If it can't resolve it via DNS,
it will attempt to look it up using NetBIOS name resolution lookups. If
its a Windoze environment (95, NT), the client will return its host name.
My guess on this one: Their hitting an NT webserver configured to log
names, not IP addresses, in the log file and the client machines don't have
Two other thoughts:
1) Keep IN-ADDR.ARPA up to date
2) Microsoft Internet Information Server only logs IP addresses, not names
given the historical slowness of reverse lookups and sloppy maintenance.
I never understood why forward and reverse maps were decoupled in DNS,
although I'm sure a good reason exists. Process Software Purveyor logs
by name (or did) and I'm not sure about Netscape's servers now.
At 02:24 PM 1/7/98 +0000, Paul Thornton wrote:
>I noticed similar port 137 hits a while back, and after a bit of
>investigating discovered that every time a colleague visited a web site
>(using Netscape, incidentally) the server sent a port 137 request back to
>the client PC.
>Initially I thought this was a "helpful" MS extension in their server, but
>have since seen port 137 hits from their nameservers as well. This probably
>points to some interesting name lookups going on at there end, which results
>in a NetBIOS name lookup being sent back. Somewhere I have the address of
>the server in question - I'll dig it out if there is interest. If nothing
>else, their hit count will go up ;-)
>Paul Thornton, Network Engineer, London Internet Exchange Ltd.
>Tel: 07000 783797 Mobile: +44 467 372205
Eric Germann Computer and Communications Technologies
ekgermann at cctec.com Van Wert, OH 45891
Phone: 419 968 2640
http://www.cctec.com Fax: 419 968 2641
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