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question about ISL vs DOT1Q

I am working on a network with a massive vlan 'd network. They are running dot1q everywhere, even though all the kit appears to be cisco. All trunks are in native VLAN 1, and trunking is allover the place.

As dot1q is a MST, this should mean that any changes to active trunks, loss of trunks, or new vlans created would knock out the STP accross the network.

Is this true, or am I being to simplistic ?

Thanks

Murray

  • Other Network Infrastructure Subjects
1 REPLY
Cisco Employee

Re: question about ISL vs DOT1Q

Cisco implements PVST even with dot1q. In other words, you have one instance of spanning-tree for each VLAN. If a trunk or link disappears somewhere, it can have an impact on spanning-tree but that may not knock out the network. For sure, SPT recalculation can occur.

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