Quick Notes - Layer2 Features

Loop Guard - Prevents alternate port and root ports from becoming designated ports. IF BPDUs are not received on a NON-DP port then the port is moved into err-disabled state

Global config - "spanning-tree loopguard default"

UDLD - Unidirectional Link Detection

- Both sides need to be configured
- default setting is disabled on copper ports and enabled on fibre ports Enable on copper ports

interface config - udld enable

Root Guard
- the port that has root guard enabled ensures that if a superior BPDU is received the port is put into "root inconsistent state"

Interface config - "spanning-tree guard root"

BPDU Guard
- Ensures that loops are not formed on ports that are enabled to use portfast, if BPDU is recieved the port is put into error disabled state. Two ways to enable BPDU Guard

Global config - "spanning-tree portfast bpduguard"
- All ports that have portfast enabled will also have BPDU guard enabled

Interface config - spanning-tree bpduguard enable"

BPDU Filter
- When enabled globally and a BPDU is received on a port the is enabled with portfast the port loses it portfast status

Global config - "spanning-tree portfast bpdufilter default"
- When enabled on the interface the port stops sending and recieveing BPDU. This is dangerous as a loop can form

Interface config - "spanning-tree bpdufilter enable"


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