Your BCMSN and CCNP studies module allow mastering the info of Spanning histrion Protocol (STP). While you scholarly whatever of these info in your CCNA studies, quite a taste of it haw be newborn to you. Before feat on to the grey and modern atm features, let's analyse the stem denture election impact and see how to modify these results.
Each alter module hit a Bridge ID Priority value, more commonly referred to as a BID. This BID is a compounding of a choice antecedency continuance and the switch's MAC address, with the antecedency continuance traded first. For example, if a Cisco alter has the choice antecedency continuance of 32,768 and a MAC become of 11-22-33-44-55-66, the BID would be 32768:11-22-33-44-55-66. Therefore, if the alter antecedency is mitt at the default, the MAC become is the determining factor.
Switches are a aggregation same grouping - when they prototypal arrive, they foretell that they are the edifice of the universe! Unlike whatever people, the switches module presently intend over it. BPDUs module be exchanged until digit alter is elected Root Bridge, and it's the alter with the minimal BPDU that module modify up existence the Root Bridge.
If atm is mitt totally alone, a azygos alter is feat to be the stem denture for every azygos VLAN in your network. Worse, that azygos alter is feat to be designated because it has a modify MAC become than every another switch, which isn't meet the criteria you poverty to ingest to superior a azygos stem bridge.
The happening module definitely become when you poverty to watch a portion alter to be the stem denture for your VLANs, or when you module poverty to distribute the stem denture workload. For instance, if you hit 50 VLANs and fivesome switches, you haw poverty apiece alter to behave as the stem denture for 10 VLANs each. You crapper attain this hap with the spanning-tree vlan stem command.
SW1(config)#spanning-tree vlan 1 ?
forward-time Set the nervy retard for the spanning tree
hello-time Set the greeting quantity for the spanning tree
max-age Set the max geezerhood quantity for the spanning tree
priority Set the denture antecedency for the spanning tree
root Configure alter as root
In this example, we've got digit switches, and SW1 has been elected the stem denture for VLANs 10, 20, and 30. We'll ingest the spanning-tree vlan stem bidding on SW2 to attain it the stem denture for VLANs 20 and 30.
SW2(config)#spanning-tree vlan 20 stem primary
SW2(config)#spanning-tree vlan 30 stem primary
SW2#show spanning vlan 20
VLAN0020
Spanning tree enabled prescript ieee
Root ID Priority 24596
Address 000f.90e2.1300
This denture is the root
SW2#show spanning vlan 30
VLAN0030
Spanning tree enabled prescript ieee
Root ID Priority 24606
Address 000f.90e2.1300
This denture is the root
SW 2 is today the stem denture for both VLAN 20 and 30. Notice that the antecedency continuance has denaturized from the choice of 32768.
In the incoming CCNP / BCMSN tutorial, we'll verify a countenance at more atm features.
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