Dont' have the HDLC packet format handy -
But in general:
For ISIS/CLNS/ESIS - the DLC header is 0xFEFE (for OSI family)
and the protocol specific fixed header for ISIS after DLC header is: 0x83
for ESIS is: 0x81
and for CLNS is: 0x80
(as per the ISO10589, ISO/TR9577)
/Shankar
! Date: Mon, 4 Jun 2001 18:24:45 -0400
! From: Sonam Thapa <aos824@yahoo.com>
!
! Hi,
!
! I didn't know which other public list to ask this
! on - cisco-nsp seemed the closest so here goes.
!
! I was wondering how one demultiplexes IS-IS
! packets over cisco-hdlc. Cisco-hdlc has a 2 byte
! protcol type which follows ethertype quite closely.
! For IS-IS packets does this protcol field have the
! value 0xFEFE (denoting OSI packets). If this is
! so, how does a system know what type of packet
! it is - IS-IS, ES-IS etc.
!
! Is there any cisco or ietf document (for use
! with protocol analyzers) available that specify
! the packet formats for cisco-hdlc in general and
! OSI packets over cisco-hdlc in particular.
!
! TIA,
! -aos
!
!
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