I was going through the IE Volume I v5 (Beta) labs and ran across the following task:
Configure sw1 as the STP Root Bridge for all active VLANs.
I’ve seen similar tasks on other IE labs. The task’s scope will depend on the phrasing:
“all VLANs” – ATP* as this could mean all possible VLANs (1-4094) or all active VLANs (see below)
“all possible VLANs” – ATP is you are running VTP as this could mean only the VLANs possible with VTP (1-1001) or all possible VLANs (1-4094)
“all active VLANs” – only the VLANs that are being used in the Layer 2 network (be sure that you have already built all of your VLANs).
* – Ask The Proctor 🙂
In this example we’re running VTP on all switches (one VTP domain). sw1 is a VTP client and all of the VLANs are built. We can get the VLANs by issuing the “show vlan brief” command:
Rack25SW1(config)#do sh vlan br
VLAN Name Status Ports
—- ——————————– ——— ——————————-
1 default active Fa0/2, Fa0/4, Fa0/6, Fa0/7
Fa0/8, Fa0/9, Fa0/10, Fa0/11
Fa0/12, Fa0/19, Fa0/20, Fa0/21
Fa0/22, Fa0/23, Fa0/24, Gi0/1
Gi0/2
5 VLAN0005 active
7 VLAN0007 active
8 VLAN0008 active
9 VLAN0009 active
10 VLAN0010 active
22 VLAN0022 active
43 VLAN0043 active
58 VLAN0058 active Fa0/5
67 VLAN0067 active
79 VLAN0079 active
146 VLAN0146 active Fa0/1
1002 fddi-default act/unsup
1003 token-ring-default act/unsup
1004 fddinet-default act/unsup
1005 trnet-default act/unsup
If there are only a handful of VLANs then you can just create a list of VLANs from this output. If there are more then I use the following method:
1) I set the switch to VTP transparent mode. That should create a configuration line with all of the VLANs listed in the “show vlan brief” output (except for VLAN 1):
Rack25SW1(config)#vtp mode trans
Setting device to VTP TRANSPARENT mode.
Rack25SW1(config)#do sh run | i vlan
vlan internal allocation policy ascending
vlan 5,7-10,22,43,58,67,79,146
switchport access vlan 146
switchport access vlan 58
2) Copy that line (adding VLAN 1 if necessary) :
Rack25SW1(config)#spanning-tree vlan 1,5,7-10,22,43,58,67,79,146 root primary
3) Put the switch back into VTP client mode:
Rack25SW1(config)#vtp mode client
Setting device to VTP CLIENT mode.
Rack25SW1(config)#do sh run | i vlan
spanning-tree vlan 1,5,7-10,22,43,58,67,79,146 priority 24576
vlan internal allocation policy ascending
switchport access vlan 146
switchport access vlan 58
To verify:
Rack25SW1(config)#do sh spannnig vlan 1 | i Address
Address 001b.d490.7c00
Address 001b.d490.7c00
Both MAC Addresses are the same (the local switch’s MAC and the root bridge’s MAC) so this is the root bridge for that VLAN. Now issue “show spanning-tree root”
Rack25SW1#sh spanning-tree root
Root Hello Max Fwd
Vlan Root ID Cost Time Age Dly Root Port
—————- ——————– ——— —– — — ————
VLAN0001 24577 001b.d490.7c00 0 2 20 15
VLAN0005 24581 001b.d490.7c00 0 2 20 15
VLAN0007 24583 001b.d490.7c00 0 2 20 15
VLAN0008 24584 001b.d490.7c00 0 2 20 15
VLAN0009 24585 001b.d490.7c00 0 2 20 15
VLAN0010 24586 001b.d490.7c00 0 2 20 15
VLAN0022 24598 001b.d490.7c00 0 2 20 15
VLAN0043 24619 001b.d490.7c00 0 2 20 15
VLAN0058 24634 001b.d490.7c00 0 2 20 15
VLAN0067 24643 001b.d490.7c00 0 2 20 15
VLAN0079 24655 001b.d490.7c00 0 2 20 15
VLAN0146 24722 001b.d490.7c00 0 2 20 15
All of the the Root MAC Addresses are the same AND they match the local switch’s MAC address so we’re golden.
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