IPX Ethernet and FDDI Encapsulation Methods

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Updated:October 4, 2005

Document ID:10690

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Ethernet Encapsulation Methods

On Ethernet you have four encapsulation formats:

Ethernet version II
Novell-specific framing
Ethernet 802.3/802.2 without SNAP
Ethernet 802.3/802.2 with SNAP

Ethernet Version II

Cisco: ipx encapsulation arpa
Novell: Ethernet_II

+-----------+--------+---------+----------

| Dst | Src |  Type  | Data...

|     |     |(0x8137)|(checksum 0xFFFF, IPX-header ...)

+-----------+--------+---------+----------

<- 6 -><- 6 -><-- 2 -->

Novell-Specific Framing (raw 802.3)

Cisco: ipx encapsulation novell-ether
Novell: Ethernet_802.3 (old-style default Novell encapsulation, versions 2.x through 3.11)

+-----------+--------+---------+----------

| Dst | Src | Length | Data...

|     |     |        | (checksum 0xFFFF, IPX-header ...)

+-----------+--------+---------+----------

<- 6 -><- 6 -><-- 2 -->

Ethernet 802.3/802.2 without SNAP

Cisco: ipx encapsulation sap (prior to Cisco IOS ver. 10.0: Novell encapsulation iso1)
Novell: Ethernet_802.2 (new-style default Novell encapsulation, versions > 3.11)

+-----------+--------+-------------+-------+---------+-----

| Dst | Src | Length | DSAP | SSAP |Control| Data...

|     |     |        |(0xE0)|(0xE0)|(0x03) |(checksum 0xFFFF, IPX-header ...)

+-----------+--------+-------------+-------+---------+-----

<- 6 -><- 6 -><- 2 ->

Ethernet 802.3/802.2 with SNAP

Cisco: ipx encapsulation snap
Novell: Ethernet_snap

+-----------+--------+-------------+-------+--

| Dst | Src | Length | DSAP | SSAP |Control|

|     |     |        |(0xAA)|(0xAA)|(0x03) |

+-----------+--------+-------------+-------+---...

                      <-----LLC2 (802.2)--->

     <-- 3 --> <-- 2 -->

...-+----------+--------+-----------

    | Org Code |  Type  | Data...

    |   OUI    |(0x8137)| (checksum 0xFFFF, IPX-header ...)

...-+----------+--------+-----------

Ethernet uses the type field to determine the packet protocol. 802.3/802.2 use the DSAP and SSAP fields.

Because there are only 256 possible SAP values, they are fairly hard to get. The special SAP number of AA was assigned to indicate that there are further headers after the 802.2 header that must be parsed to determine the network-level protocol. This is the SNAP header that uses the same type field used by V2 Ethernet.

Examples

IP on an Ethernet can be indicated by Ethernet V2 type 0x0800, 802.2 SAP code 0x06; or a SAP code of 0xAA followed by a SNAP type code of 0x0800.

AppleTalk can be indicated by either Ethernet V2 type 0x809B (Phase I), or a SAP code of 0xAA followed by a SNAP type code of 0x809B (Phase II). AppleTalk is currently never sent as an 802.3/802.2 packet with a unique SAP code.

Novell can be found as either Ethernet type 0x8137, or a raw 802.3 packet. It is not sent as an 802.3/802.2 packet with a unique SAP code.

There are only a few SAP values that you are likely to run across. They are:

04 - IBM SNA
06 - IP
80 - 3Com
AA - SNAP
BC - Banyan
E0 - Novell (TR)
F4 - Lan Manager FE - CLNS

FDDI Encapsulation Methods

On FDDI you have only three encapsulation formats:

FDDI-raw
FDDI with LLC
FDDI with LLC and SNAP

FDDI-Raw

Cisco: ipx encapsulation fddi-raw (IOS 11.1.x and up)
Novell: FDDI_raw (used only from third-party vendors, not from Novell)

+-----------+--------+---------+----------

| Dst | Src | Length | Data...

|     |     |        | (checksum 0xFFFF, IPX-header ...)

+-----------+--------+---------+----------

<- 6 -><- 6 -><-- 2 -->

FDDI with LLC

Cisco: ipx encapsulation sap (prior IOS 10.0: Novell encapsulation iso1)
Novell: FDDI_802.2

+-----------+--------+-------------+-------+---------+-----

| Dst | Src | Length | DSAP | SSAP |Control| Data...

|     |     |        |(0xE0)|(0xE0)|(0x03) |(checksum 0xFFFF, IPX-header ...)

+-----------+--------+-------------+-------+---------+-----

<- 6 -><- 6 -><- 2 ->

FDDI with LLC and SNAP

Cisco: ipx encapsulation snap (default IPX encapsulations on FDDI from Cisco)
Novell: FDDI_snap (default encapsulation on FDDI Novell servers)

+-----------+--------+-------------+-------+--

| Dst | Src | Length | DSAP | SSAP |Control|

|     |     |        |(0xAA)|(0xAA)|(0x03) |

+-----------+--------+-------------+-------+---...

                      <-----LLC2 (802.2)--->

     <-- 3 --> <-- 2 -->

...-+----------+--------+-----------

    | Org Code |  Type  | Data...

    |   OUI    |(0x8137)| (checksum 0xFFFF, IPX-header ...)

...-+----------+--------+-----------

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