Vlan removed after the switch reload.

[Farooq Razzaque]

Dear Team

I have an access switch (C2960S-48FPS-L) which is running on version (universalk9-mz.122-55.SE5).

This switch was running on VTP client mode and connected to distribution switch running on VTP client mode and vtp version 3, due to power failure the switch got reloaded and after reload it come to VTP server mode and all the vlans were deleted, but the SVI of the vlan and all other config was still there.

In show vtp status it is showing vtp prunning is disabled but in interfaces parameters it is showing (Pruning VLANs Enabled: 2-1001)

Does VTP pruning will restrict the switch to become VTP client again after the reload even if the configuration is saved

Or it is causing by known bug.

sh vtp status 
VTP Version capable             : 1 to 3
VTP version running             : 1
VTP Domain Name                 : 
VTP Pruning Mode                : Disabled
VTP Traps Generation            : Enabled

Name: Gi1/0/1

Switchport: Enabled
Administrative Mode: trunk
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
Administrative private-vlan host-association: none 
Administrative private-vlan mapping: none 
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk Native VLAN tagging: enabled
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk associations: none
Administrative private-vlan trunk mappings: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001

[Leo Laohoo · Accepted solution]

This switch was running on VTP client mode and connected to distribution switch running on VTP client mode and vtp version 3, due to power failure the switch got reloaded and after reload it come to VTP server mode and all the vlans were deleted, but the SVI of the vlan and all other config was still there.

You say the switch is on VTP mode client.  So this means that as a "client" the switch receives VLAN information from a switch with VTP mode server.  Your output to "VTP Domain" is blank.  This means the switch will NOT get any VLAN information because your VTP domain is blank.

[Farooq Razzaque]

Dear Leo

Thanks for your reply.

Please ignore the previous vtp status output that was mistakenly posted.

Following is the output of show vtp status after the switch restarted and came in server mode. Earlier it was configured with VTP mode 'client' and vtp domain as well.

DCC-CCTV-IDF29-2F-ASW01#sh vtp status 
VTP Version capable             : 1 to 3
VTP version running             : 1
VTP Domain Name                 : 
VTP Pruning Mode                : Disabled
VTP Traps Generation            : Enabled
Device ID                       : 8875.5638.1600
Configuration last modified by 0.0.0.0 at 0-0-00 00:00:00
Local updater ID is 0.0.0.0 (no valid interface found)

Feature VLAN:
--------------
VTP Operating Mode                : Server
Maximum VLANs supported locally   : 255
Number of existing VLANs          : 5
Configuration Revision            : 0
MD5 digest                        : 0x57 0xCD 0x40 0x65 0x63 0x59 0x47 0xBD 
                                    0x56 0x9D 0x4A 0x3E 0xA5 0x69 0x35 0xBC 

[Leo Laohoo]

Following is the output of show vtp status after the switch restarted and came in server mode. Earlier it was configured with VTP mode 'client' and vtp domain as well.

Ok, you can't just change from VTP client to VTP server.  Not that easy.  

The only way for you to go from VTP client to VTP server very, very quickly (and destructively) is by deleting the VLAN.dat file.  If this is what was done, then all your VLAN information gets erased.

[Farooq Razzaque]

Previously this switch was running on VTP client mode and connected to distribution switch running on VTP client mode and vtp version 2, due to power failure the switch got reloaded and after reload it come to VTP server mode automatically and all the vlans were deleted, but the SVI of the vlan and all other config was still there.

[Farooq Razzaque]

Hello all

I checked the vlan.dat file which was taken 1 week before the switch reload. I saw that vlans are saved in vlan.dat file but still after the reload all vlans got deleted from vlan.dat file and switch came to vtp mode server automatically.

Today the same issue happened with other switch (WS-C2960S-48FPS-L) running the same version.

In past we have faced the same issues many times with different switches located on diff location.

I want to know is this related to bug.

[Farooq Razzaque]

Dear Team

I noticed the following error during switch reload. 

"%SW_VLAN-4-BAD_VLAN_CONFIGURATION_FILE: VLAN configuration file contained incorrect verification word:[hex]."

Anybody have any idea what is the cause of this error

[Farooq Razzaque]

Hello Leo and all

I checked the vlan.dat file which was taken 1 week before the switch reload. I saw that vlans are saved in vlan.dat file but still after the reload all vlans got deleted from vlan.dat file and switch came to vtp mode server automatically.

Today the same issue happened with other switch (WS-C2960S-48FPS-L) running the same version.

In past we have faced the same issues many times with different switches located on diff location.

I want to know is this related to bug.

[Farooq Razzaque]

Dear All,

Any idea on this issue. Have anybody faced this issue.

Awaiting response