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vlan.dat

under construction…

Structure

Offset	Bytes	Type	IOS Name	Values	Notes
000	4	string	-	BADB10	Magic Number?
004	4	int	VTP Version	2, 3	-
008	1	char	VTP Operating Mode ID	1 (client), 2 (server), 3 (transparent)	-
009	1	char	-		VTP Domain Name Length
00a	32	string	VTP Domain Name		-
02b	6	?	Configuration Revision	-	-
030	4	int	Local updater ID		IP address
034	4	int	Last update on		vlan interface with lowest number
038	12	string	Configuration last modified by		yymmddhhmmss
044	8	bytes	MD5 digest		-
04c	8	?	?		-
054	1	char	-		VTP Password Length
055	64	string	VTP Password		-
095	3	int	Number of existing VLANs		this may be 2 bytes not 3. There should be enough VLANs with two bytes: 2^(8*2)-1 = 65535. ~~I add a 0-byte at the beginning and treat it as int~~
098	8	?	?		-
Repeats for each VLAN ¹⁾
0a0	1	char	Name Length
0a1	32	string	Name
0c1	2	short	Type	1 (enet), 2 (fddi), 3 (trcrf), 4 (fdnet), 5 (trbrf)	may is just a char, not short. would be enough, but no idea what the first byte could be
0c3	1	char	State	1 (active), 2 (suspended)
0c4	2	short	MTU	576-18190
0c6	2	short	ID	1 to 4094	Extended-range VLANs (VLAN IDs 1006 to 4094) are only saved in the VLAN database in VTP version 3.
0c8	4	int	SAID	1 to 4294967294
0d8	2	short	Ring Number	1-4095	FDDI or Token Ring
?	1	char	Bridge Number	0-15	FDDI Net or Token Ring Net
?	1	char	STP Type	0 (none), 1 (ieee), 2 (ibm)	FDDI Net or Token Ring
?	2	short	Parent VLAN	0-1005	FDDI or Token Ring
?	8	?	?
?	1	char	Remote SPAN	0 (disabled), 1 (enabled)
?	1	char	?
Following Stuff is yet unknown
…	96	?	?	?	?

I got most of the information from Chris Welsh (decoding vlan.dat). Thank you.

Notes About Missing Parts

VLAN

http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst2960x/software/15-0_2_EX/vlan/configuration_guide/b_vlan_152ex_2960-x_cg/b_vlan_152ex_2960-x_cg_chapter_011.html

1)

Remote SPAN (enabled, disabled) ⇒ char (1)
VLAN state (active, suspend) ⇒ char (1)
Translational bridge 1 (0 to 1005) ⇒ short (2)
Translational bridge 2 (0 to 1005) ⇒ short (2)

or: 2)

Parent (Parent VLAN, if one exists.)
RingNo (Ring number for the VLAN, if applicable.)
BridgeNo (Bridge number for the VLAN, if applicable.)
Stp (Spanning-Tree Protocol type used on the VLAN.)
BrdgMode (Bridging mode for this VLAN—Possible values are source-route bridging (SRB) and source-route transparent bridging (SRT); the default is SRB.)
Trans1 (see below)
Trans2 (see below)

trans1 & trans2:

Types of translational bridges that the VLAN in the VLAN column is configured to translate to. Translational bridge VLANs must be a VLAN media type different from the affected VLAN; if two VLANs are specified, each one must be a different type.
Common VLAN types include Ethernet (enet), FDDI (fdnet), and Token Ring (tnet). The numbers in the Trans1 and Trans2 columns refer to the VLAN ID numbers of the translational bridge VLANs.
Note The term VLAN translation is also used in Cisco configuration guides for mapping specific VLANs in a given trunk to another VLAN that is of the same media type. In this context the term VLAN translation refers to a form of VLAN mapping that is using the term VLAN translation to describe it.

– http://www.cisco.com/c/en/us/td/docs/ios/lanswitch/command/reference/lsw_book/lsw_s2.html

it looks like this is Token Ring information… so, rather 2) than 1). http://www.cisco.com/c/en/us/td/docs/ios/12_2/ibm/configuration/guide/fibm_c/bcftrrsm.html

Script output - known fields:

1003 token-ring-default               trcrf 1500 101003
1004 fddinet-default                  fdnet 1500 101004
1005 trnet-default                    trbrf 1500 101005

Script output - unknown fields:

b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x07\x07\x00\x00\x00'
b'\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
b'\x00\x00\x00\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'

show vlan output:

1003 tr    101003     1500  -      -      -        -    srb      0      0
1004 fdnet 101004     1500  -      -      1        ieee -        0      0
1005 trnet 101005     1500  -      -      1        ibm  -        0      0

Cisco Docs input

show vlan fields

You can set these parameters when you create a new normal-range VLAN or modify an existing VLAN in the VLAN database:

VLAN ID
VLAN name
VLAN type
- Ethernet
- Fiber Distributed Data Interface [FDDI]
- FDDI network entity title [NET]
- TrBRF or TrCRF
- Token Ring
- Token Ring-Net
VLAN state (active or suspended)
Maximum transmission unit (MTU) for the VLAN
Security Association Identifier (SAID)
Bridge identification number for TrBRF VLANs
Ring number for FDDI and TrCRF VLANs
Parent VLAN number for TrCRF VLANs
Spanning Tree Protocol (STP) type for TrCRF VLANs
VLAN number to use when translating from one VLAN type to another

– http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst2960x/software/15-0_2_EX/vlan/configuration_guide/b_vlan_152ex_2960-x_cg/b_vlan_152ex_2960-x_cg_chapter_011.html#task_87763697237543969FD3A444933A282E

Information in IOS

VLAN Information

affe#sh vl

VLAN Name                             Status    Ports
---- -------------------------------- --------- -------------------------------
1    default                          active    Gi1/0/1, Gi1/0/2, Gi1/0/3, Gi1/0/4, 
                                                Gi1/0/22, Gi1/0/23, Gi1/0/25, Gi1/0/26
3    VLAN0003                         active
5    VLAN0005                         active
50   Affe                             active
52   Banane                           active    Gi1/0/13, Gi1/0/14
915  Entensuppe                       active
1002 fddi-default                     act/unsup
1003 token-ring-default               act/unsup
1004 fddinet-default                  act/unsup
1005 trnet-default                    act/unsup

VLAN Type  SAID       MTU   Parent RingNo BridgeNo Stp  BrdgMode Trans1 Trans2
---- ----- ---------- ----- ------ ------ -------- ---- -------- ------ ------
1    enet  100001     1500  -      -      -        -    -        0      0

VLAN Type  SAID       MTU   Parent RingNo BridgeNo Stp  BrdgMode Trans1 Trans2
---- ----- ---------- ----- ------ ------ -------- ---- -------- ------ ------
3    enet  100003     1500  -      -      -        -    -        0      0
5    enet  100005     1500  -      -      -        -    -        0      0
50   enet  100050     1500  -      -      -        -    -        0      0
52   enet  100052     1500  -      -      -        -    -        0      0
915  enet  100915     1500  -      -      -        -    -        0      0
1002 fddi  101002     1500  -      -      -        -    -        0      0
1003 tr    101003     1500  -      -      -        -    srb      0      0
1004 fdnet 101004     1500  -      -      1        ieee -        0      0
1005 trnet 101005     1500  -      -      1        ibm  -        0      0


Remote SPAN VLANs
------------------------------------------------------------------------------


Primary Secondary Type              Ports
------- --------- ----------------- ------------------------------------------

VTP Configuration / Status

affe#sh vtp status
VTP Version capable             : 1 to 3
VTP version running             : 1
VTP Domain Name                 : ENTENSUPPE
VTP Pruning Mode                : Disabled
VTP Traps Generation            : Disabled
Device ID                       : a2a3.2b63.ef21
Configuration last modified by 192.168.2.230 at 10-21-16 16:41:50
Local updater ID is 192.168.1.200 on interface Vl1 (lowest numbered VLAN interface found)

Feature VLAN:
--------------
VTP Operating Mode                : Server
Maximum VLANs supported locally   : 255
Number of existing VLANs          : 42
Configuration Revision            : 321
MD5 digest                        : 0x00 0x11 0x22 0x33 0x44 0x55 0xE4 0x66
                                    0x77 0x88 0x99 0xAA 0xBB 0xCC 0xDD 0xEE

Abbreviations

Abbreviation	written-out
BRF	Bridge Relay Function
TrCRF	Token Ring Concentrator Relay Function
TrBRF	Token Ring Bridge Relay Function

Links

¹⁾

for number of iterations see Number of existing VLANs from above

defect.ch - Wiki

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