Volume 1 Version 5 Switching Labs

This weekend I have been going through some of the switching labs. Alot of the switching im quite comfortable with so I didnt want to waste any time. Today I focused on 802.1Q tunneling, and setting up Port-channel using PagP over a 802.1q tunnel. That was kind of interesting.

Next I worked on something as simple as root guard. I configured Switch 1 as the spanning-tree root for all VLAN's. I then configured the trunk links to Switch 2 and Switch 3 with the spanning-tree guard root command. So, this way if another switch connected in our layer 2 network starts advertising a BPDU claiming they are the root for one of the VLAN's it will put our port in a root inconsistent state for that VLAN's that the switch is claiming they are root for. So to test this functionality, I configured switch 4 as with a spanning-tree priority 0 for VLAN 1, and 10. Sure enough as soon as I did that, Switch 1 received that BPDU. When I issued the command show spanning-tree detail I saw that VLAN 1 and VLAN 10 were Root inconsistent. Next to further Verify VLAN 1, and 10 were in root inconsistent I configured SVI's on Switch 1 and 2 for VLAN 1. I tried pinging between the two and was unable to even though the interfaces were up/up. I configured SVI's on switch 1 and switch 2 for VLAN 138 (which did not receive a superior BPDU and was not in the root inconsistent state and was able to ping. Next I told Switch 4 not to be root for VLAN's 1 and 10. Switch one immediately noticed this, and came out of the root inconsistent states.

I just wanted to see how the L2 network would behave when this occured. I also noticed, that when the VLAN's were root inconsistent on SW1, SW2 and SW3 believed SW4 was Root for those VLAN's. Interesting!!