4 Replies Latest reply: Jan 9, 2012 5:10 AM by Olushile Akintade CCIE R&S RSS

    VTP PRUNING (CONFUSED)

    prince

      I'm doing some INE labs and got to VTP pruning and paused for a moment. Any help would be appreciated. Hope you can visualize this.

       

       

      I've got 4 switches connected as follows:

       

      sw1 <-> sw2

      sw1 <-> sw3

       

      sw1<-> sw4

      basicall sw2, sw3, and sw4 connect to sw1 and has 3 links to each switch

       

       

      sw2 is my vtp server and the rest are clients

       

      i turned on vtp pruning and then the confusion started

       

      Sw2 has vlan 8, vlan 22 defined on the switch

       

      Rack1SW2#sh run int vlan 8

      Building configuration...

       

      Current configuration : 59 bytes

      !

      interface Vlan8

      ip address 155.1.8.8 255.255.255.0

      end

       

      Rack1SW2#

       

      Rack1SW2#sh run int f0/24

      Building configuration...

       

      Current configuration : 61 bytes

      !

      interface FastEthernet0/24

      switchport access vlan 22

      end

       

      CONFUSION (AT LEAST TO ME) BELOW

       

      if these two vlans are defined on this switch then why are they showed as forwarding.

       

      Rack1SW2#

       

      Rack1SW2#sh int trunk

       

      Port        Mode             Encapsulation  Status        Native vlan

      Fa0/13      auto             n-802.1q       trunking      1

      Fa0/14      auto             n-802.1q       trunking      1

      Fa0/15      auto             n-802.1q       trunking      1

       

      Port        Vlans allowed on trunk

      Fa0/13      1-4094

      Fa0/14      1-4094

      Fa0/15      1-4094

       

      Port        Vlans allowed and active in management domain

      Fa0/13      1,5,7-10,22,43,58,67,79,146

      Fa0/14      1,5,7-10,22,43,58,67,79,146

      Fa0/15      1,5,7-10,22,43,58,67,79,146

       

      Port        Vlans in spanning tree forwarding state and not pruned

      Fa0/13      1,7,9-10,43,58,67,79,146

      Fa0/14      1

      Fa0/15      1

      Rack1SW2#

       

      also if it's not forwarding why is i see  output for said vlans

       

       

      Rack1SW2#sh spanning-tree vlan 8

       

      VLAN0008

        Spanning tree enabled protocol ieee

        Root ID    Priority    32776

                   Address     000b.be1a.6300

                   Cost        38

                   Port        15 (FastEthernet0/13)

                   Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

       

        Bridge ID  Priority    32776  (priority 32768 sys-id-ext 8)

                   Address     0017.0e3f.4080

                   Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

                   Aging Time  300 sec

       

      Interface           Role Sts Cost      Prio.Nbr Type

      ------------------- ---- --- --------- -------- --------------------------------

      Fa0/13              Root FWD 19        128.15   P2p

      Fa0/14              Altn BLK 19        128.16   P2p

      Fa0/15              Altn BLK 19        128.17   P2p

       

       

      Rack1SW2#

       

       

      Rack1SW2#sh spanning-tree vlan 22

       

      VLAN0022

        Spanning tree enabled protocol ieee

        Root ID    Priority    32790

                   Address     000b.be1a.6300

                   Cost        38

                   Port        15 (FastEthernet0/13)

                   Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

       

        Bridge ID  Priority    32790  (priority 32768 sys-id-ext 22)

                   Address     0017.0e3f.4080

                   Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

                   Aging Time  300 sec

       

      Interface           Role Sts Cost      Prio.Nbr Type

      ------------------- ---- --- --------- -------- --------------------------------

      Fa0/2               Desg FWD 19        128.4    P2p

      Fa0/13              Root FWD 19        128.15   P2p

      Fa0/14              Altn BLK 19        128.16   P2p

      Fa0/15              Altn BLK 19        128.17   P2p

      Fa0/24              Desg FWD 100       128.26   Shr

       

       

      Rack1SW2#

       

       

       

       

      On another switch (see below) vlan 22 doesn't leave switch2 the devices in vlan 22 are directed attached to sw2, but sw1 shows the vlan as forwarding on port13 (which connects to sw2) vtp pruning show prune this vlan correct??

       

      Rack1SW1#sh int trunk

       

      Port        Mode             Encapsulation  Status        Native vlan

      Fa0/13      desirable        802.1q         trunking      1

      Fa0/14      desirable        802.1q         trunking      1

      Fa0/15      desirable        802.1q         trunking      1

      Fa0/16      desirable        802.1q         trunking      1

      Fa0/17      desirable        802.1q         trunking      1

      Fa0/18      desirable        802.1q         trunking      1

      Fa0/19      desirable        802.1q         trunking      1

      Fa0/20      desirable        802.1q         trunking      1

      Fa0/21      desirable        802.1q         trunking      1

       

      Port        Vlans allowed on trunk

      Fa0/13      1-4094

      Fa0/14      1-4094

      Fa0/15      1-4094

      Fa0/16      1-4094

      Fa0/17      1-4094

      Fa0/18      1-4094

      Fa0/19      1-4094

      Fa0/20      1-4094

      Fa0/21      1-4094

       

      Port        Vlans allowed and active in management domain

      Fa0/13      1,5,7-10,22,43,58,67,79,146

      Fa0/14      1,5,7-10,22,43,58,67,79,146

      Fa0/15      1,5,7-10,22,43,58,67,79,146

      Fa0/16      1,5,7-10,22,43,58,67,79,146

      Fa0/17      1,5,7-10,22,43,58,67,79,146

      Fa0/18      1,5,7-10,22,43,58,67,79,146

      Fa0/19      1,5,7-10,22,43,58,67,79,146

      Fa0/20      1,5,7-10,22,43,58,67,79,146

      Fa0/21      1,5,7-10,22,43,58,67,79,146

       

      Port        Vlans in spanning tree forwarding state and not pruned

      Fa0/13      8,22,43,58

      Fa0/14      none

      Fa0/15      none

      Fa0/16      1,9,43,79

      Fa0/17      none

      Fa0/18      none

      Fa0/19      10,146

      Fa0/20      none

      Fa0/21      none

      Rack1SW1#

        • 1. Re: VTP PRUNING (CONFUSED)
          Paul Stewart  -  CCIE Security

          You might want to include the "show vlan brief" output with the above show commands as well.  I am guessing that this has something to do with the fact that your vlan 8 on sw2 is just a management interface and doesn't include a real layer 2 instance.  I wouldn't have thought it would have pruned it because I can see a valid use case for this. 

          • 2. Re: VTP PRUNING (CONFUSED)
            prince

            here's the vlan brief output

             

             

            Rack1SW2#sh vlan brief

             

            VLAN Name                             Status    Ports

            ---- -------------------------------- --------- -------------------------------

            1    default                          active    Fa0/1, Fa0/3, Fa0/4, Fa0/5

                                                            Fa0/6, Fa0/7, Fa0/8, Fa0/9

                                                            Fa0/10, Fa0/11, Fa0/12, Fa0/16

                                                            Fa0/17, Fa0/18, Fa0/19, Fa0/20

                                                            Fa0/21, Fa0/22, Fa0/23, Gi0/1

                                                            Gi0/2

            5    VLAN0005                         active   

            7    VLAN0007                         active   

            8    VLAN0008                         active   

            9    VLAN0009                         active   

            10   VLAN0010                         active   

            22   VLAN0022                         active    Fa0/2, Fa0/24

            43   VLAN0043                         active   

            58   VLAN0058                         active   

            67   VLAN0067                         active   

            70   VLAN0070                         active   

            79   VLAN0079                         active   

            146  VLAN0146                         active   

            1002 fddi-default                     act/unsup

            1003 token-ring-default               act/unsup

             

            VLAN Name                             Status    Ports

            ---- -------------------------------- --------- -------------------------------

            1004 fddinet-default                  act/unsup

            1005 trnet-default                    act/unsup

            Rack1SW2#

            • 3. Re: VTP PRUNING (CONFUSED)
              prince

              added note that makes sense. That might be why vlan 22 doesn'tshow on this link. Becuase vlan 22 is local to this switch it wan't be forwarding for vlan 22 on f0/13,but then that doesn't explain why sw1 shows forwarding for vlan 22 back to sw2. If sw2 pruned vlan 22 why does sw1 show it forwarding.

              • 4. Re: VTP PRUNING (CONFUSED)
                Olushile Akintade CCIE R&S

                sw1 is forwarding because its most likely the root bridge for vlan 22(and probably for all the vlans in this lab). Do a show spanning-tree vlan 8 and 22 on sw1 and post it here. A root bridge will have all its ports in forwarding.