I'd just like to add something to this.
An Jon mentioned, the file is in const_nvram:
6500-3(config)#do dir const_nvram:
Directory of const_nvram:/
1 -rw- 856 vlan.dat
129004 bytes total (128148 bytes free)
However, deleting this will only delete VLANs in the standard (not extended) range.
Here's a quick illustration:
6500-3(config)#do sh vlan
VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
1 default active
100 VLAN0100 active
105 VLAN0105 active
110 VLAN0110 active
115 VLAN0115 active
120 VLAN0120 active
1002 fddi-default act/unsup
1003 token-ring-default act/unsup
1004 fddinet-default act/unsup
1005 trnet-default act/unsup
3000 VLAN3000 active
3005 VLAN3005 active
3010 VLAN3010 active
3015 VLAN3015 active
3020 VLAN3020 active
3025 VLAN3025 active
As you can see, I have the default vlans, and additionally I have vlans 100,105,110,115,120 in the standard range, and 3000,3005,3010,3015,3020,3025 in the extended range.
In VTP Server mode, the extended VLANs appear in the configuration and the standard ones do not:
6500-3(config)#do sh vtp stat | i Operating
VTP Operating Mode : Server
6500-3(config)#do sh run | i vlan
vlan internal allocation policy ascending
vlan access-log ratelimit 2000
vlan 3000,3005,3010,3015,3020,3025
In VTP Transparent mode, they all appear in the config:
6500-3(config)#vtp mode trans
Setting device to VTP TRANSPARENT mode.
6500-3(config)#do sh run | i vlan
vlan internal allocation policy ascending
vlan access-log ratelimit 2000
vlan 100,105,110,115,120,3000,3005,3010,3015,3020,3025
Looking at the VLAN.dat file (through the jibberish), you will see that only standard vlans are stored here:
6500-3(config)#do more const_nvram:vlan.dat
6500-3(config)#do more const_nvram:vlan.dat
:[^P
^@^@^@^B^B^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@@(
^C^@^@^@^A100106004016 {KU^_ 'go"^C^Ke;V|^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@
^B^B^@^@P,^Fhdefault^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^A^A^E\^@^A^@^A^F!^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^VLAN0100^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^A^A^E\^@d^@^A^D^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^VLAN0105^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^A^A^E\^@i^@^A ^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^VLAN0110^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^A^A^E\^@n^@^A^N^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^VLAN0115^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^A^A^E\^@s^@^A^S^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^VLAN0120^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^A^A^E\^@x^@^A^X^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^Lfddi-default^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^B^A^E\^Cj^@^A
^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^Rtoken-ring-default^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^C^A^E\^Ck^@^A
^K^@^@^@^@^@^@^@^@^@^@^@^@^@^@^Ofddinet-default^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^D^A^E\^Cl^@^A
^L^@^@^@^A^@^@^@^@^@^@^@^@^@^@^@^@
trnet-default^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^E^A^E\^Cm^@^A
^@^@^@^B^@^@^@^@^@^@^@^@^@^@^@^@F^VP^@^@^Cj^@^@^BVkx^A^A^@^@^D^A^@^@F^`^@^@^Ck^@^@^S^\^PP^A^A^@^@^D^A^@^@S+B ^@^@^Cl^@^@^C^^P^B^A^@^@^C^A^@^A^@^@^@^@^@^@^Cm^@^@^F^S^LX^B^A^@^@^C^A^@^B
The long and short: to delete vlans typically I like to just do a 'no vlan 1-4094':
6500-3(config)#no vlan 1-4094
Default VLAN 1 may not be deleted.
Default VLAN 1002 may not be deleted.
Default VLAN 1003 may not be deleted.
Default VLAN 1004 may not be deleted.
Default VLAN 1005 may not be deleted.
6500-3(config)#do sh vlan
VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
1 default active
1002 fddi-default act/unsup
1003 token-ring-default act/unsup
1004 fddinet-default act/unsup
1005 trnet-default act/unsup