Kevin Dorrell, CCIE #20765

17 Feb 2008

NMC Lab 7.15 – Catalyst Specialties (VTP)

Filed under: VTP — Tags: — dorreke @ 04:42

The Answer Key (page 46) makes the statement:

NOTE: Make sure that client device don’t have VLAN.DAT with vlan information on  its flash, since this will prevent VTP domain from correct synchronisation.

AFAIK, this simply is not true.  So let’s try it.  Let us start with CAT1 as server and CAT2 as client, just like in the book.  We currently have a VLAN.DAT on the flash of CAT2.  BTW, don’t worry about  the fact that the last updater is 192.168.42.1; I keep an address on VLAN 1 at all times so I can synchronise to the NTP clock on my home network.

CAT1#show vtp status 
VTP Version                     : 2 
Configuration Revision          : 4 
Maximum VLANs supported locally : 1005 
Number of existing VLANs        : 12 
VTP Operating Mode              : Server 
VTP Domain Name                 : NMC 
VTP Pruning Mode                : Enabled 
VTP V2 Mode                     : Enabled 
VTP Traps Generation            : Disabled 
MD5 digest                      : 0xBD 0xAF 0xE2 0xB8 0x8A 0x8E 0xD4 0x90 
Configuration last modified by 192.168.42.110 at 2-12-08 05:51:22 
Local updater ID is 192.168.42.110 on interface Vl1 (lowest numbered VLAN interface found) 
CAT1#

Here is CAT2’s view: 

CAT2#show vtp status 
VTP Version                     : 2 
Configuration Revision          : 4 
Maximum VLANs supported locally : 1005 
Number of existing VLANs        : 12 
VTP Operating Mode              : Client 
VTP Domain Name                 : NMC 
VTP Pruning Mode                : Enabled 
VTP V2 Mode                     : Enabled 
VTP Traps Generation            : Disabled 
MD5 digest                      : 0xBD 0xAF 0xE2 0xB8 0x8A 0x8E 0xD4 0x90 
Configuration last modified by 192.168.42.110 at 2-12-08 05:51:22 
CAT2#

CAT2 has a VLAN.DAT in its flash at the moment. 

CAT2#show flash Directory of flash:/  

  : 
  414  drwx         128  Mar 01 1993 06:34:20 +01:00  Lab06 
  413  -rwx         984  Mar 01 1993 01:13:21 +01:00  vlan.dat 
  418  drwx         128  Mar 01 1993 01:39:18 +01:00  Lab04 
  415  drwx         128  Mar 01 1993 02:52:21 +01:00  Lab25 
  425  drwx         128  Mar 01 1993 10:08:23 +01:00  Lab03 
  428  drwx         128  Feb 03 2008 16:16:54 +01:00  Lab05 
  431  -rwx        4248  Mar 01 1993 01:16:10 +01:00  config.text 
  434  -rwx        1092  Mar 01 1993 01:16:10 +01:00  private-config.text 
  437  -rwx        1048  Mar 01 1993 01:16:10 +01:00  multiple-fs 15998976 bytes total (2173952 bytes free) 
CAT2#

 Now let us try adding a VLAN at CAT1:

CAT1#conf t 
Enter configuration commands, one per line.  End with CNTL/Z. 
CAT1(config)#vlan 42 
CAT1(config-vlan)#name Test 
CAT1(config-vlan)#exit 
CAT1(config)#exit 
CAT1# 
Feb 17 03:20:58.967: %SYS-5-CONFIG_I: Configured from console by console

Let us check it on CAT1: 

CAT1#show vtp status 
VTP Version                     : 2 
Configuration Revision          : 5 
Maximum VLANs supported locally : 1005 
Number of existing VLANs        : 13 
VTP Operating Mode              : Server 
VTP Domain Name                 : NMC 
VTP Pruning Mode                : Enabled 
VTP V2 Mode                     : Enabled 
VTP Traps Generation            : Disabled 
MD5 digest                      : 0xC7 0xD4 0x08 0x2D 0xB6 0xC9 0xB0 0x15 
Configuration last modified by 192.168.42.110 at 2-17-08 03:20:57 
Local updater ID is 192.168.42.110 on interface Vl1 (lowest numbered VLAN interface found) 
CAT1#

Let us check it on CAT2:

CAT2#show vtp status 
VTP Version                     : 2 
Configuration Revision          : 5 
Maximum VLANs supported locally : 1005 
Number of existing VLANs        : 13 
VTP Operating Mode              : Client 
VTP Domain Name                 : NMC 
VTP Pruning Mode                : Enabled 
VTP V2 Mode                     : Enabled 
VTP Traps Generation            : Disabled 
MD5 digest                      : 0xC7 0xD4 0x08 0x2D 0xB6 0xC9 0xB0 0x15 
Configuration last modified by 192.168.42.110 at 2-17-08 03:20:57 
CAT2#

Well, CAT2 seems to have updated OK despite having a VLAN.DAT in the flash.  Let us see what happens if we delete the VLAN.DAT:

CAT2#delete vlan.dat 
Delete filename [vlan.dat]? 
Delete flash:vlan.dat? [confirm]

Check it is gone: 

CAT2#show flash Directory of flash:/  

    2  -rwx     4968676  Mar 01 1993 01:11:43 +01:00  c3550-i5k2l2q3-mz.121-22.EA4.bin 
    3  drwx         192  Mar 01 1993 05:03:30 +01:00  Lab01 
    4  drwx          64  Mar 01 1993 02:54:02 +01:00  Lab24 
  412  drwx         128  Mar 01 1993 01:35:11 +01:00  Lab02 
    8  drwx         128  Aug 30 2007 14:00:06 +02:00  c3550-ipbasek9-mz.122-40.SE 
    6  -rwx           0  Mar 01 1993 01:14:32 +01:00  env_vars 
    7  -rwx          44  Mar 01 1993 01:14:32 +01:00  system_env_vars 
  411  -rwx        2637  Mar 01 1993 01:03:15 +01:00  default.cfg 
  414  drwx         128  Mar 01 1993 06:34:20 +01:00  Lab06 
  418  drwx         128  Mar 01 1993 01:39:18 +01:00  Lab04 
  415  drwx         128  Mar 01 1993 02:52:21 +01:00  Lab25 
  425  drwx         128  Mar 01 1993 10:08:23 +01:00  Lab03 
  428  drwx         128  Feb 03 2008 16:16:54 +01:00  Lab05 
  431  -rwx        4248  Mar 01 1993 01:16:10 +01:00  config.text 
  434  -rwx        1092  Mar 01 1993 01:16:10 +01:00  private-config.text 
  437  -rwx        1048  Mar 01 1993 01:16:10 +01:00  multiple-fs 15998976 bytes total (2174976 bytes free)

Now let us try updating the domain again on CAT1: 

CAT1#conf t 
Enter configuration commands, one per line.  End with CNTL/Z. 
CAT1(config)#no vlan 42 
CAT1(config)#^Z 
CAT1# 
Feb 17 03:23:40.846: %SYS-5-CONFIG_I: Configured from console by console

The change has propagated to CAT2: 

CAT2#show vtp status 
VTP Version                     : 2 
Configuration Revision          : 6 
Maximum VLANs supported locally : 1005 
Number of existing VLANs        : 12 
VTP Operating Mode              : Client 
VTP Domain Name                 : NMC 
VTP Pruning Mode                : Enabled 
VTP V2 Mode                     : Enabled 
VTP Traps Generation            : Disabled 
MD5 digest                      : 0x7E 0xCC 0x4B 0x16 0x85 0x92 0xD5 0xF7 
Configuration last modified by 192.168.42.110 at 2-17-08 03:23:39

But here is an interesting thing: CAT2 has recreated the VLAN.DAT

CAT2#show flash Directory of flash:/ 
    2  -rwx     4968676  Mar 01 1993 01:11:43 +01:00  c3550-i5k2l2q3-mz.121-22.EA4.bin 
    3  drwx         192  Mar 01 1993 05:03:30 +01:00  Lab01 
    4  drwx          64  Mar 01 1993 02:54:02 +01:00  Lab24 
  412  drwx         128  Mar 01 1993 01:35:11 +01:00  Lab02 
    8  drwx         128  Aug 30 2007 14:00:06 +02:00  c3550-ipbasek9-mz.122-40.SE 
    6  -rwx           0  Mar 01 1993 01:14:32 +01:00  env_vars 
    7  -rwx          44  Mar 01 1993 01:14:32 +01:00  system_env_vars 
  411  -rwx        2637  Mar 01 1993 01:03:15 +01:00  default.cfg 
  414  drwx         128  Mar 01 1993 06:34:20 +01:00  Lab06 
  413  -rwx         984  Feb 17 2008 04:23:39 +01:00  vlan.dat 
  418  drwx         128  Mar 01 1993 01:39:18 +01:00  Lab04 
  415  drwx         128  Mar 01 1993 02:52:21 +01:00  Lab25 
  425  drwx         128  Mar 01 1993 10:08:23 +01:00  Lab03 
  428  drwx         128  Feb 03 2008 16:16:54 +01:00  Lab05 
  431  -rwx        4248  Mar 01 1993 01:16:10 +01:00  config.text 
  434  -rwx        1092  Mar 01 1993 01:16:10 +01:00  private-config.text 
  437  -rwx        1048  Mar 01 1993 01:16:10 +01:00  multiple-fs 15998976 bytes total (2173952 bytes free) 
CAT2#

Now that is interesting.  We deleted the VLAN.DAT from CAT2.  But as soon as we went back to CAT1 and modified the domain (deleting the extra VLAN we created), the VLAN.DAT was recreated on CAT2.

It is logical that a client should keep a copy of the VLAN.DAT.  Suppose the client got isolated from the rest of the network and then rebooted.  If it didn’t have a copy of the VLAN.DAT, then it would lose all its VLANs.

CAT2#show vtp status 
VTP Version                     : 2 
Configuration Revision          : 0 
Maximum VLANs supported locally : 1005 
Number of existing VLANs        : 5 
VTP Operating Mode              : Server 
VTP Domain Name                 : 
VTP Pruning Mode                : Disabled 
VTP V2 Mode                     : Disabled 
VTP Traps Generation            : Disabled 
MD5 digest                      : 0x57 0xCD 0x40 0x65 0x63 0x59 0x47 0xBD 
Configuration last modified by 0.0.0.0 at 0-0-00 00:00:00 
Local updater ID is 192.168.42.120 on interface Vl1 (lowest numbered VLAN interface found) 
CAT2#

Not only that, but it would not know the VTP password any more.  That means that it would not be able to connect to the VTP server any more.

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