Different spanning tree instances in a single network
I have a new network with one Catalyst 4506, several 3Com Bay Gigabit Ethernet switches and Bay 450T swtiches. The over network network is configured as a star topology with the Catalyst 4506 as the hub and those 3Com Gigabit Ethernet switches as spoke. Those Bay 450T switches are connected to 3Com switches. I am afraid that there may be several spanning tree instances in this network which cannot be compatible with each other. May I ask what is the best way to config this new network? Disable spanning tree in Cisco device? Disable spanning tree in all those non Cisco devices? Or Treat each spoke as different layer 3 subnets? Pls give some advice on it.
Re: Different spanning tree instances in a single network
If the Cisco Catalyst 4506 is the heart of your network, and you are in a star topology with 3Com and then Bay/Nortel 450T switches branching out from there, then if there are no redundant connections between switches you do not actually need STP on any of them.
Treating each spoke as different Layer 3 subnets or VLAN can be useful, especially if you have one per building in a multi-building environment. Or one VLAN/subnet per floor, in a multiple-floor building. Ideally, keep the size of each VLAN to less than 200 to 250 devices (such as servers, workstations, printers).
If you do have redundant connections, however, or you want to run STP in case you unexpectedly create one (for example, a crossover cable in two ports on the same VLAN on the same switch), then making the 4506 your STP root bridge/switch would be best. Give it a really low bridge priority, like 10 (default is 32768, numbers can range from 0 to 65535), so it's guaranteed to win the election process. Active links in your Spanning Tree(s) will then proceed radially from the center of your network out to the edges.
How are your VLANs distributed? Where are your redundant connections, if any? Since you're dealing with a multi-vendor environment, you will have to use 802.1Q VLAN tagging on any VLAN trunk ports from the Cisco. And probably, just a single instance of Spanning Tree to apply to all VLANs on the network.
Make sure all switch-to-switch connections are VLAN trunk ports. Make sure VLAN 1 is present on each trunk (automatic with Cisco switches; manually done with the 3Com and Bay/Nortel, as I remember). All the other VLANs on a trunk port you can customize, so that you are not sending VLAN broadcast traffic across links to switches where no ports are assigned in those VLANs (unless those VLANs need to use the trunk loop for redundancy purposes).
The Spanning Tree from the Cisco on VLAN 1 will be the Mono Spanning Tree that the other non-Cisco switches use, and will apply to all of the VLANs on those switches.
In summary, use VLAN 1 on all your switches. Keep the users off it, if you can. Use VLAN trunks between the switches. And Spanning Tree should sort itself out fine. Know where your blocked ports are, so you can diagram how each VLAN's Spanning Tree looks when it's working, and which way traffic will flow when a link fails.
This is actually a pretty cool feature, i didn't even know it existed until I was looking for a solution to advertise a subnet (prefix in BGP talk), only if a certain condition existed. This is exactly what conditional advertisements does
j ai une question j ai achete un routeur cisco 887VA-k9 , je le configuré avec la configuration ci- dessous
si je le lier avec mon pc portable sur l un de ses ports directement ça marche toute est bien ( la connexion internet + m...
Attached policy provides CLI access to the Cisco 4G router over text messaging. Two files are in the attached .tar file:
2. PDF with instructions on how to load and use the .tcl file.