VLANs not cleared from trunk (Switch Audit)

[David Marquez]

  Hi,   

I´m working on a switch audit and I´m confused on this exception  "VLANs not cleared from trunk". I know i have the Recommendation and Corrective Action, but I don´t know how to look for those Vlans that I have to remove.

I mean, Which command Do I need to use in the swith ? How can I see Vlan that isn´t being used ? 

Exception	Description	Recommendation	Reference URL(s)	Network Elements Affected
VLANs not cleared from trunk	Clearing VLANs from Trunks helps prevent STP being propogated to switches that don't need it for that VLAN	Cisco recommends pruning VLANs from trunks where they are not needed to maximize STP stability.	Layer 2 LAN Ports **	Router(config-if)# switchport trunk allowed vlan {none \|{{add \| except \| remove} vlan[,vlan[,vlan[,...]]}}

** URL: http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SX/configuration/guide/layer2.html 

  Thanks for reading this

[paul driver · Accepted solution]

Hello

can you confirm what vlans your trying to remove

As swithces have internal vlans which cannot be removed

sh vlan-internal-usage

Enabling pruning would dynamically remove unused vlans however I find myself his isn't as deterministic as manually pruning vlans

show int trunk = will show You the vlans allowed to cross the trunk and active

Sh vlan brrief = will show what  interfaces are assigned to the vlan

Res

paul

[David Marquez]

   Hello my friend,

 I used the command above, and I get this..

show vlan internal usage

VLAN Usage
---- --------------------
1006 online diag vlan0
1007 online diag vlan1
1008 online diag vlan2
1009 online diag vlan3
1010 online diag vlan4
1011 online diag vlan5
1012 PM vlan process (trunk tagging)
1013 Control Plane Protection
1014 Partial shortcut vlan
1015 vrf_0_vlan
1016 IPv6-mpls RSVD VLAN
1017 Egress internal vlan
1018 Multicast VPN 0 QOS vlan
1019 IPv6 Multicast Egress multicast 

Show Vlan Brief  

                VLAN    Name    Status    Ports                                            
----    --------------------------------    ---------    -------------------------------                                            
1    default    active    Gi5/1,    Gi6/1,    Gi6/20                                    
2    BACKBONE_MZ    active    Gi12/4,    Gi12/5,    Gi12/24,    Gi12/25,    Gi12/26,    Gi12/36,    Gi13/5,    Gi13/6,    Gi13/24,    Gi13/25,    Gi13/26    
3    INTER-ROUTING    active                                                
5    AP    active    Gi12/13,    Gi12/14,    Gi12/15,    Gi12/16,    Gi13/13,    Gi13/14,    Gi13/15,    Gi13/16                
7    BACKBONE_MZ_2    active    Gi7/2,    Gi8/2,    Gi12/43,    Gi12/44,    Gi13/36,    Gi13/43,    Gi13/44,    Gi13/47,    Gi13/48            
10    TP    active                                                
13    DIR    active    Gi12/2,    Gi13/2                                        
15    TANGO    active    Gi12/1,    Gi12/6,    Gi12/10,    Gi12/11,    Gi12/12,    Gi13/1,    Gi13/3,    Gi13/10,    Gi13/11            
20    EVD    active                                                
25    VoiceM    active    Gi12/22,    Gi12/23,    Gi13/22,    Gi13/23                                
30    DIR-GESTION    active    Gi12/3,    Gi13/4                                        
41    Gestion_A1_TEMPORAL    active    Gi12/33                                            
59    VIR-ICE_(IT)    active    Gi12/27,    Gi12/28,    Gi12/29,    Gi12/30,    Gi12/39,    Gi12/42,    Gi13/27,    Gi13/28,    Gi13/29,    Gi13/30,    Gi13/39,    Gi13/42
63    O&M    active    Gi12/9,    Gi13/9                                        
65    Tx    active    Gi5/18,    Gi6/18                                        
88    IT-SERVICES    active                                                
89    O&M_Tx    active                                                
510    VOICE_3    active                                                
528    Probe_1    active    Gi12/35,    Gi13/35                                        
532    O&M_Lx    active    Gi12/37,    Gi12/38,    Gi12/45,    Gi12/46,    Gi13/37,    Gi13/38,    Gi13/45,    Gi13/46                
533    O&M_PBR    active    Gi12/31,    Gi12/32,    Gi12/40,    Gi12/41,    Gi13/31,    Gi13/32,    Gi13/33,    Gi13/40,    Gi13/41            
534    IP-GESTION    active    Gi12/34,    Gi13/34                                        
542    IP-DATOS    active                                                
572    USED_FOR_NETWORK_MGMT    active                                                
578    Ix_RO    active                                                
579    ET_Guest    active                                                
586    ET_Datos    active                                                
600    Gestion_NER    active                                                
612    Gestion_Rx_NER    active                                                
730    IPL2-GESTION    active                                                
881    IP_TP_SIG    active                                                
883    IP_DL_OyM    active                                                
1000    MetroEthernet_BBO    active                      

show interfaces trunk

Port                Mode         Encapsulation  Status        Native vlan
Gi5/5               on           802.1q         trunking      1
Gi5/14              on           802.1q         trunking      1
Gi5/16              on           802.1q         trunking      1
Gi5/20              on           802.1q         trunking      1
Gi6/5               on           802.1q         trunking      1
Gi6/14              on           802.1q         trunking      1
Gi6/16              on           802.1q         trunking      1
Gi12/19             on           802.1q         trunking      1
Gi13/19             on           802.1q         trunking      1
Po1                 on           802.1q         trunking      1
Po2                 on           802.1q         trunking      1
Po3                 on           802.1q         trunking      1

Port                Vlans allowed on trunk
Gi5/5               1-4094
Gi5/14              1,10,20
Gi5/16              542,730,881,883
Gi5/20              2,579,586,612
Gi6/5               1-4094
Gi6/14              1,10,20
Gi6/16              542,730,881,883
Gi12/19             88-89
Gi13/19             88-89
Po1                 1-4094
Po2                 1-83,85-89,91-4094
Po3                 1-83,85-89,91-4094

Port                Vlans allowed and active in management domain
Gi5/5               1-3,5,7,10,13,15,20,25,30,41,59,63,65,88-89,510,528,532-534,542,572,578-579,586,600,612,730,881,883,1000
Gi5/14              1,10,20
Gi5/16              542,730,881,883
Gi5/20              2,579,586,612
Gi6/5               1-3,5,7,10,13,15,20,25,30,41,59,63,65,88-89,510,528,532-534,542,572,578-579,586,600,612,730,881,883,1000
Gi6/14              1,10,20
Gi6/16              542,730,881,883
Gi12/19             88-89
Gi13/19             88-89
Po1                 1-3,5,7,10,13,15,20,25,30,41,59,63,65,88-89,510,528,532-534,542,572,578-579,586,600,612,730,881,883,1000
Po2                 1-3,5,7,10,13,15,20,25,30,41,59,63,65,88-89,510,528,532-534,542,572,578-579,586,600,612,730,881,883,1000
Po3                 1-3,5,7,10,13,15,20,25,30,41,59,63,65,88-89,510,528,532-534,542,572,578-579,586,600,612,730,881,883,1000

Port                Vlans in spanning tree forwarding state and not pruned
Gi5/5               1-3,5,7,10,13,15,20,25,30,41,59,63,65,88-89,510,528,532-534,542,572,578-579,586,600,612,730,881,883,1000
Gi5/14              1,10,20
Gi5/16              542,730,881,883
Gi5/20              2,579,586,612
Gi6/5               1-3,5,7,10,13,15,20,25,30,41,59,63,65,88-89,510,528,532-534,542,572,578-579,586,600,612,730,881,883,1000
Gi6/14              1,10,20
Gi6/16              542,730,881,883
Gi12/19             88-89
Gi13/19             88-89
Po1                 1-3,5,7,10,13,15,20,25,30,41,59,63,65,88-89,510,528,532-534,542,572,578-579,586,600,612,730,881,883,1000
Po2                 1-3,5,7,10,13,15,20,25,30,41,59,63,65,88-89,510,528,532-534,542,572,578-579,586,600,612,730,881,883,1000
Po3                 1-3,5,10,13,15,20,30,41,63,65,578,1000 

   Do I have to check these interfaces Gi5/5  ; Gi6/5 ; Po1 ; Po2 ; Po3  ???

[Madhukrishnan Gopinathan Nair]

Hello David,

You can check the below on the switch which will show you the vlans and the ports associated with them. If you do not have any ports for a vlans listed, I assume it is safe for you to remove that vlan from trunk.

sh vlan 

Hope this helps, 

Madhu.

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[jhager001]

just enable Vlan pruning if your VTP is successfully implemented (or implemented at all)