Hello Christian (/George),
This definitely helps. However, I just wanted to
verify that I understood you correctly. An ISIS
packet over cisco-hdlc will look as follows -
[0x0f][0x00][0xFEFE][0x83][protocol data]
^ There is no 0x03 here right?
A related question - cisco hdlc is generally used
over lower speed links OC-3 and below. I am wondering
if I should expect regulart PPP at OC-12 and above
links.(At least that is what I see in vendor data
sheets.)
Thanks again,
-aos
--- "Martin, Christian" <cmartin@gnilink.net> wrote:
> Here is the breakdown (thanks to George Matey for
> this!)
>
>
> --------------
> The first ("address") octet is set to 0x0F for
> unicast packets and 0x8F for
> broadcast packets. Broadcast just means that the
> higher-level protocol
> thought this was a broadcast packet; cisco doesn't
> support multidrop HDLC at
> this time.
>
> The second ("control") octet is always 0.
>
> The next two octets are a 16-bit protocol code, sent
> most-significant-first.
> These codes are usually Ethernet type codes. cisco
> has added some codes to
> support packet types that don't appear on Ethernets.
> The current list of
> codes is as follows:
>
> TYPE_PUP 0x0200 PUP
> TYPE_XNS 0x0600 XNS
> TYPE_IP10MB 0x0800 IP
> TYPE_CHAOS 0x0804 Chaos
> TYPE_IEEE_SPANNING 0x4242 DSAP/SSAP
> for IEEE spanning prot.
> TYPE_DECNET 0x6003 DECnet phase
> IV
> TYPE_BRIDGE 0x6558 Bridged
> Ethernet/802.3 packet
>
> TYPE_APOLLO 0x8019 Apollo
> domain
> TYPE_REVERSE_ARP 0x8035 cisco SLARP
> (not real reverse ARP!)
>
> TYPE_DEC_SPANNING 0x8038 DEC bridge
> spanning tree protocol
>
> TYPE_ETHERTALK 0x809b Apple
> EtherTalk
> TYPE_AARP 0x80f3 Appletalk
> ARP
> TYPE_NOVELL1 0x8137 Novell IPX
> TYPE_CLNS 0xFEFE ISO CLNP/ISO
> ES-IS DSAP/SSAP
>
> This list is shared between serial and Ethernet
> encapsulations. Not all
> these codes will necessarily appear on serial lines.
> This list will probably
> be extended as cisco adds support for more
> protocols.
>
> Bytes after this are higher-level protocol data.
> These normally look the
> same as they'd look on Ethernet. Bridging packets
> include Ethernet/802.3 MAC
> headers; no other packets do.
> --------------
>
> HTH,
> chris
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