number of vlans in an mst instance

dondej

does anyone know how many, or is their a limit to the number of vlans in an mst instance? not mst0 as this has all vlans anyway. The max i've seen configured is 500

Mrock4

If I'm not mistaken, the max amount of MST instances is 16, with the amount of vlans being mapped to each one unlimited. To be honest though, I can't find any documentation at the moment, so I'd like to see some if somebody has any.

Forsaken_GA

I'm pretty sure that the number of vlan's you can map to an instance is only limited by the number of vlans that the switch will support.

Netwurk

Forsaken_GA wrote: »

I'm pretty sure that the number of vlan's you can map to an instance is only limited by the number of vlans that the switch will support.

Sounds right to me. If the default instance can accept all VLANs, then adding more instances isn't likely to limit the number of VLANs an instance can handle.

Good question though, got me thinking

dondej

thanks guys, i'm due to implement an mst config with 6 instances each with 500 vlans mapped to an instance, thought it might be quicker to have just 2 with vlans split between them since i'm only using two distributions switches and will have 2 mst priorities

instance 1 vlan 100-199, 300-399, 500-599, 700-799, 900-999
instance 2 vlan 2-99, 200-299, 400-499, 600-699, 800-899
instance 3 vlan 1100-1199,1300-1399,1500-1599,1700-1799,1900-1999
instance 4 vlan 1000-1099,1200-1299,1400-1499,1600-1699,1800-1899
instance 5 vlan 2100-2199,2300-2399,2500-2599,2700-2799,2900-2999
instance 6 vlan 2000-2099,2200-2299,2400-2499,2600-2699,2800-2899

spanning-tree mst 0 priority 0
spanning-tree mst 1 priority 24576
spanning-tree mst 2 priority 28672
spanning-tree mst 3 priority 24576
spanning-tree mst 4 priority 28762
spanning-tree mst 5 priority 24576
spanning-tree mst 6 priority 28762

Mrock4

The only question I'd raise with 6 instances is- will your network be able to fully reap the benefits of having 6 instances (logical topologies) ?? If not, there is not much a difference between those and 2 instances, depending on the physical topology. Especially if those MST instances are going to share the same logical topology.

Another thing is that although by default all VLANS are mapped to IST, hardly any of those are active on the links. You could load the instance with VLAN mappings but actually having data pass through on that instance is another story.