About the Mib2 ifIndex numbering scheme used by the DFE

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Article ID: 5456 

Products
DFE 

Goals
Determine logical port number from MIB-2 ifIndex value
Interface Numbering Scheme Explained 

Cause
The ifIndex values show up as Instance information for all of the branches under the MIB 'ifEntry=1.3.6.1.2.1.2.2.1'. Knowing the formulation of the ifIndex field can be useful in determining the (typically) cli-referencing logical port number that corresponds to the entry in question. 

Solution
You can find the MIB ifIndex at ifIndex=1.3.6.1.2.1.2.2.1.1, defined as 
  ifIndex  OBJECT-TYPE
SYNTAX INTEGER
ACCESS read-only
STATUS mandatory
DESCRIPTION
"A unique value, greater than zero, for each
interface. It is recommended that values are assigned
contiguously starting from 1. The value for each
interface sub-layer must remain constant at least from
one re-initialization of the entity's network
management system to the next re-initialization."
:: = { ifEntry 1 }
--1.3.6.1.2.1.2.2.1.1

The ifIndex numbering scheme for the DFE is as follows: 

If one digit long... 
  x
|_ (1=host, 2=loopback)

If five digits long... 
  x x x x x
| | |_|_|_ 3-digit physical Port number
| |_______ 1-digit Media type (1=fe, 2=ge, 5001=com, 5100=FTM1, 5501=rtr)
|_________ 1-digit Slot number

If seven digits long... 
  1 0 0 5 x x x
| | | | |_|_|_ 3-digit LAG Port number (format 'lag.x.xx')
|_|_|_|_______ 4-digit LAG port indicator 0x1005

Examples:
    12001 = gigabit port#1 on slot 1 = ge.1.1
    1005001 = lag.0.1 (valid range lag.0.1-lag.0.48)
Much of this is reflected in the port descriptions as listed in 'ifDescr=1.3.6.1.2.1.2.2.1.2'. It also ties into the "MIB2 Interface" and "Port" numbering descriptions of a 'show port counters' query: 
  DFE(su)->show port counters

Port: host.0.1 MIB2 Interface: 1 Bridge Port: 1
Counter Discontinuity: 6 days 15 hours 26 minutes 38 seconds ago
--------------------------------------------------------------------

MIB2 Interface Counters
-----------------------
In Octets 5775059
In Unicast Pkts 40205
In Multicast Pkts 0
In Broadcast Pkts 1612
In Discards 0
In Errors 0
In Unknown Protocol 0
Out Octets 9509286
Out Unicasts Pkts 41319
Out Multicast Pkts 94
Out Broadcast Pkts 0
Out Errors 0
Out Queue Length 0

802.1Q Switch Counters
----------------------
Frames Received 41817
Frames Transmitted 41413
Frames Filtered 18

Port: lo.0.1 MIB2 Interface: 2
Counter Discontinuity: 6 days 15 hours 26 minutes 38 seconds ago
--------------------------------------------------------------------

MIB2 Interface Counters
-----------------------
In Octets 118012470
In Unicast Pkts 617438
In Multicast Pkts 0
In Broadcast Pkts 0
In Discards 0
In Errors 0
In Unknown Protocol 0
Out Octets 118015358
Out Unicasts Pkts 617454
Out Multicast Pkts 0
Out Broadcast Pkts 0
Out Errors 0
Out Queue Length 0

Port: fe.1.1 MIB2 Interface: 11001 Bridge Port: 64
No counter discontinuity time
--------------------------------------------------------------------

MIB2 Interface Counters
-----------------------
In Octets 0
In Unicast Pkts 0
In Multicast Pkts 0
In Broadcast Pkts 0
In Discards 0
In Errors 0
In Unknown Protocol 0
Out Octets 0
Out Unicasts Pkts 0
Out Multicast Pkts 0
Out Broadcast Pkts 0
Out Errors 0
Out Queue Length 256

802.1Q Switch Counters
----------------------
Frames Received 0
Frames Transmitted 0
Frames Filtered 0

. . .

DFE(su)->

For an explanation of the "Bridge Port" numbering description (generally only used for Traps) of a 'show port counters' query, see 5567

See also: 5441.
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