Month: April 2020

STP Root Bridge, Root Port, Path Selections, STP Timers:

Lowest Bridge ID becomes Root Bridge
Bridge Priority, System ID Extension, MAC Address

Standard VLAN range is 1-1005
Vlan1 – default ethernet access vlan and default 802.1q, native vlan
can not be deleted but can be manually pruned from trunks
can not be pruned by VTP (vlan trunking protocol)
should not be used for actual port assignments

VLANs 1002-1005
default legacy token ring, fddi vlans
can not be deleted but can be manually pruned from trunks
can not be pruned by VTP
should not be used for actual port assignments

Extended VLANS
range 1006-4094
normally used for transparent mode or VTP version 3
Not all extended vlans can be used, some are reserved for internal use

Internal VLANS
reserved for internal applications, native layer 3 switchports
sh vl intern usa
Not all platforms agree on internal range, for deployments, check internal allocations, some allocate ascending, some descending

Enabled by default on some platforms

DTP Desirable Mode – initiate trunking negotiation,
sw mo dyn des
sw mo tru

DTP Auto Mode – passively listen for trunking negotiation
sw mo dyn aut