200 301 exam objectives

200 301 exam objectives.The switch will still set the first 4 digits of the BID based on the configured value. It turns out that the first 4 digits of each of the 16 multiples of 4096 in the interval from 0 all the way up to 61440 have different binary values: 0000, 0001, 0010, etc., all the way up to the llll switch opportunityoThe true 4-bit priority is configured based on the first 4 bits of the configured value.Although historical reasons and configurations may make the concept of BID priority seem a little complex, in practice, adding a 12-bit field to the BID achieves good results because it can be used to identify the VLAN IDO VLANIDs range from 1 to 4096,12 bits are required.Cisco switches keep the VLANID in the System ID extension field. Therefore, each switch will have a unique BID for each VALN.For example, for a switch configured with VLAN1 through VLAN4, the default base priority is 32768, the default STP priority for VLAN1 is 32769, VLAN2 is 32770, VLAN3 is 32771, and so on. Therefore, in addition to the VLAN ID, consider the 16-bit priority as the base priority (for example, the spanning-tree vlan vlan-idpriority x configuration command).Per-VLAN port overheadEach switch interface configures its per-VLAN STP overhead by default based on the IEEE recommendations listed in Table 1-6 in Chapter 1 of this book. For interfaces that support multiple speeds, the Cisco switch selects the current actual speed. Therefore, if the interface chooses a lower speed, then the default STP overhead will also respond at the lower speed. If the interface chooses to use a different speed, then the switch also dynamically changes the STP port overhead accordingly.In addition to this, the switch's STP ports can also be configured using the spanning-tree [vlan vlan-id] cost cost interface subcommand. This command is often used on trunk devices because setting overhead on a trunk has an impact on the root overhead of the switch, but setting STP on an access port does not have this impact.For the command itself, which may or may not include the VLANID, the The command simply requires a vlan parameter on the trunk port in order to set the perVLAN overhead. On a trunk, if the command ignores the VLAN parameter, it sets STP overhead for all those VLANs that are not set overhead with the spanning-tree vlan xcost command.Summary of STP Configuration Options Table 2-2 summarizes the default settings for BID and port overhead. along with a list of the optional configuration commands introduced in this chapter.