CCNA 2 - Capitulo 5 - Supplemental Module 1.4

CCNA 2 - Capitulo 5 - Supplemental Module 1.4

1. MECHANISM PROVIDE STP STABILITY MECHANISM

   • ROOT GUARD
     • ENFORCES THE ROOT BRIDGE PLACEMENT
     • WHATS IS PURPOSE ?
       • MITIGATE RISK OF ACCIDENTAL OR INTENTIONAL ROOT BRIDGE MANIPULATION
       • ENSURE THAT NO UNAUTHORIZES SWITCH CAN BECOME THE ROOT BRIDGE
     • ROOT-GUARD-ENABLED PORT RECEIBES BPDUs SUPERIOR THE CURRENT BRIDGE?
       • PORT IS MOVED TO A ROOT-INCONSISTENT STATE (WILL BLOCK TRAFFIC TO PREVENT UNAUTHORIZES SWI INFLUENCING TOPOLOGY )
         • IS EQUAL TO AN STP LISTENING STATE AND NO TRAFFIC IS SENDING
         • RECOVER AUTATICALLY AFATER PORT STOP RECEIVING SUPERIOR BPDUs
       • SWITCH LOGS EVENT PORT BEING PLACED INTO AN ERROR DISABLED
     • EXAMPLE : ROOT GUARD
       • IS ENABLE USING IN INTERFACE CONFIGURATION COMMAND
         • S1(CONFIG-IF)#SPANNING-TREE GUARD ROOT
           • SINCE ALL THE PORTS ON THE ROOT BRIDGE ARE DESIGNATED, THE COMMAND MUST BE ASSIGNED TO ALL PORTS.
     • CHECK IF IT IS ENABLED?
       • S1# SHOW SPANNING-TREE INTERFACE FA0/23 DETAIL
   • UDLD (UNIDIRECTIONAL LINK DETECTION)
     • DETECTS UNIDIRECTIONAL
       • LINKS BETWEEN SWITCHES
     • PREVENTS FORWARDING LOOPS WHEN TRAFFIC FLOW
       • ONLY ONE DIRECTION
   • BRIDGE ASSURANCE
     • IF BPDU ARE NOT RECEIVED ON A DESIGNATED PORT FOR CERTAIN PERIOD ?
       • PORT TRANSITIONS TO BLOCKING STATE
     • ENSURE THE HEALTH OF THE STP TOPOLOGY BY EXCHANGING BPDUs
       • BETWEEN SWITCHES ON DESIGNATED PORTS
   • LOOP GUARD
     • UNIDIRECTIONAL LINK FAILURE ?
       • SWITCH TO STOP RECEIVING BPDUs FROM ITS NEIGHBOR ON THAT LINK
         • IN PLACES THE PORT INTO A "loop-consistent" STATE
     • MONITORS BPDU EXCHANGED BETWEEN SWITCHES ON DESIGNATED PORTS
     • WHATS IS PURPOSE ?
       • PREVENT ALTERNATE OR ROOT PORT ON P2P FROM BECOMIMG DESIGNATED PORTS BECAUSE OF A
         • UNIDIRECTIONAL LINK FAILURE
     • LOOP GUARD AND ROOT GUARD SHOULD BE CONFIGURED TOGETHER
     • EXAMPLE - CONFIGURE LOOP GUARD
       • GLOBALLY
         • S1(CONFIG)# SPANNING-TREEE LOOPGUARD DEFAULT
         • P2P LINKS
       • INTERFACE
         • S1(CONFIG-IF)#SPANNING-TREE GUARD LOOP