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From: jac@umd5.umd.edu (Joseph A. Cimmino Jr.)
Newsgroups: comp.protocols.tcp-ip.ibmpc,comp.sys.ibm.pc.rt
Subject: Re: IBM PC TCP/IP talking to 4.3/RT over Token Ring?
Message-ID: <1995@umd5.umd.edu>
Date: Tue, 13-Oct-87 13:10:29 EDT
Article-I.D.: umd5.1995
Posted: Tue Oct 13 13:10:29 1987
Date-Received: Thu, 15-Oct-87 02:16:05 EDT
References: <186@cunixc.columbia.edu>
Reply-To: jac@umd5 (Joseph A. Cimmino Jr.)
Organization: University of Maryland, College Park
Lines: 29
Summary: U gotta SNAP the RT too!
Xref: mnetor comp.protocols.tcp-ip.ibmpc:2 comp.sys.ibm.pc.rt:2

In article <186@cunixc.columbia.edu> alan@cunixc.columbia.edu (Alan Crosswell) writes:
>Has anyone succeeded in getting 5798-FAL TCP/IP for the PC to talk
>to ACIS 4.3/RT?  It looks like they are using incompatible ARP
>implementations.

No, the arps aren't incompatible.  As the frame below shows, the RT is
still using the old style SAP 6/99 for IP/ARP.  The PC code uses the
new (rfc 990/1010) SNAP encapsulation.  To enable this on the RT,
use "ifconfig lan0 snap bridge".

 >
 >10 40 ff ff ff ff ff ff 7f ff 81 00 08 e5 00 00
 >AC FC ---destination--- ------source----- -----
 >
 >00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 >--- space reserved for routing information ----
 >
 >99 99 03 00 06 08 00 06 04 00 01 7f ff 81 00 08
 >-SAP- Cl ----- ARP Header ------ ----Source---->
 >
 >e5 80 3b 25 01 00 00 00 00 00 00 80 3b 25 02
 >-- -RT's addr-                   -PC's addr-
 >   128.59.37.1                   128.59.37.2
 >
------------------------------
Joseph A. Cimmino, Jr.    University of Maryland, Systems    jac@umd5.umd.edu
1+ 301 454 2946                   PC/IP Group              cimminoj@umdd.bitnet

Bertolt Brecht:  You made your bed, so you lie in it.