200 y 301

200 y 301.is the BID of the lowest adjacent object 0SW1's BID has a lower value than SW2's. so here SW3 chooses its G0/1 interface as its RP. the last two R?arbitration rules come into play only when two switches are connected to each other via multiple links. as shown in Figure 2-9. In this case. the switch will receive more than one hello from the same neighboring switch and therefore the BIDs will be the same.Overhead =19 Priority 112 Root SwitchFaO/1SW1 bridgeFaO/17SW2 bridge ID 32769:0211.1111.1111 Overhead = 19 priority 128 32769:0200.0002.0002 Figure 2-9 Topology required for the last two arbitration rules of the RPIn this particular example, SW2 becomes the root switch and SW1 needs to select its RP.SW1 has the same port overhead of 19, so SW1 has the same root overhead of 19 on each path.SW2 sends hello to SW1 on each link, so SW1 cannot select the root port based on SW1's neighbor BID, since both list SW2's Therefore, SW1 must use the other two "arbitration rules".Tip: In practice, most administrators will put these two links into the Ethernet channel.The next Arbitration Rule is a configurable option: Adjacent Switch Port Priority on each adjacent switch interface. The default setting for Cisco switch ports is 128, with values ranging from. to 255, and the smaller the better (usually). In this example, the network administrator uses the spanning-tree vlan 10 port-priority112 command when setting SW2's F0/16. SW1 knows that the top link of the adjacent object has a port priority of 112 and the bottom is 128, so SW1 uses its top (F0/14) interface as its root port.If the port priorities are the same, which is usually the case when using default values, STP defers to the internal port number of the adjacent object. The Cisco switch will assign an internal integer to identify each interface on the switch. The non-root switch looks for the lowest internal port value of the adjacent object (as shown in the hello message) and selects the RP based on the lower value.