CCNA 2 - Capitulo 5.1

CCNA 2 - Capitulo 5.1

1. STP - SPANNING TREE PROTOCOL ( 802.1D)

   • STP OPERATIONS
     • STEPS TO A LOOP FREE TOPOLOGY
       • 1 ) ROOT BRIDGE
         • SWITCH LOWEST BID
         • STA - SPANNING TREE ALGORITHM CHOSE
           • 1 - SINGLE SWITCH AS THE ROOT BRIDGE
           • 1.2 WHE SELECT ROOT BRIDGE SELECTED IS REFERENCE POINT FOR ALL PATH
         • ELETCTING PROCESS
           • 2) AFTER ROOT BRIDGE ELECT , THE STP DETERMINING BEST PATHS TO THE ROOT BRIDGE
             • HOW IS THE COST OF THE PORT IS DETERMINED?
               • NOTE : THE PORT COST IS CONFIGURABLE
               • SPEED THE PORT OPERATES
             • HOW IS THIS DONE?
               • THE SUM OF ALL THER INDIVIDUAL PORT COSTS ALONG TRE PATH
           • 1) AFTER A SWITCH BOOT , THE SWITCHES SEND OUT BPDUS ADVERTISING THEMSELVES AS THE ROOT BRIDGE.
             • BPDU FRAMES - CONTAIN
               • BID - SWITCH OF THE SENDING
               • BID - ROOT BRIDGE (ROOT BRIDGE)
                 • AT THE FIRST , ALL SWITCHES DECLARE THEMSELVES AS THE ROOT BRIDGE
             • SEND OUT BPDU FRAMES EVERY TWO SECONDS
           • 1.2) AFTER THE BPDU ANNOUNCEMENTS FROM ALL SWITCHES, WILL BE
             • THE LOWEST BID ELECTED AS THE ROOT BRIDGE.
       • 2) ROOT PORT ROLE (FORWARDING STATE)
         • ELECT A ROOT PORT FROM MULTIPLE EQUAL-COST PATHS ?
           • 1) LOWEST SENDER BID
             • BRIDGES IDS OF THE NEIGHBORING FOR BREAK THE TIE
           • 2) LOWEST SENDER PORT PRIORITY
           • 3) LOWEST SENDER PORT ID
         • WHAT IS IT ?
           • PORT CLOSEST TO THE ROOT BRIDGE
             • IN TERMS OF OVERALL COST
         • THE PATH COST
         • STA ALGORITHM IS USED THE SELECT ROOT PORT (LOWEST PATH COST TO REACH THE ROOT BRIDGE)
       • 3) DESIGNATED PORT ROLE (FORWARDING STATE)
         • ALL PORTS = DESIGNATED PORTS
           • IN ONE END OF A SEGMENT IS A ROOT PORT , THEN THE OTHER IS A DESIGNATED PORT
         • EVERY SEGMENT BETWEEN TWO SWITCHES
           • WILL HAVE ONE DESIGNATED PORT
         • BEST PATH TO RECEIVE TRAFFIC LEADING TO THE ROOT BRIDGE
         • WHAT IS NOT ROOT PORT OR DESIGNATED PORT = ALTERNATIVE OR BLOCKED
         • END DEVICES = DESIGNATED PORTS
         • DESIGNATED PORT WHEN THERE IS NO ROOT PORT ?
         • SAME PATH COST TO THE ROOT BRIDGE ?
           • ALGORITHM WILL USE THE BRIDGE ID AS A TIE BREAKER
       • 4) NON DESIGNATED PORT / ALTERNATIVE PORT ROLE BLOCKED (BLOCKING)
         • IT'S THE PORT THAT PREVENTS THE LOOP.
         • IF A PORT IS NOT A ROOT PORT OR DESIGNATED PORT
           • THEN BECOMES AN ALTERNATIVE OR BACKUP
         • BEETWEEN SWITCH - ONE DESIGNATED PORT AND ONE ROOT PORT
     • BPDUs - BRIDGE PRIORITY ID BRIDGE
       • WHATS IS BPDUs ?
         • SWITCHES SHARE INFORMATION
           • ABOUT THEMSELVES AND THEIR CONNECTIONS
       • BPDUS ARE USED ELECT WHO ?
         • ROOT BRIDGE , ROOT PORT , ROOT DESIGNATED , ALTERNATIVE PORTs
       • WHATS IS BRIDGE ID ?
         • IDENTIFIES WHICH SWITCH SENT THE BPDU
       • BID MAKING STA DECISIONS
         • ROOT BRIDGE AND PORT ROLE
       • LOWEST BID VALUE - COMBINATION TREE FIELDS - BRIDGE ID WITH THE EXTENDED SYSTEM ID
         • 1) BRIDGE PRIORITY ( 4 bits )
           • IDENTIFY SWITCH SEND BPDU
           • DEFAUT
             • 32768
             • 1.IMPACT OF DEFAULT BIDs ?
               • IT IS POSSIBLE FOR TWO OR MORE SWITCHES TO HAVE SAME PRIORITY
             • 2.HOW DO WE SOLVE THIS?
               • LOWEST MAC SWITCH WILL BECOME ROOT BRIDGE
             • 3.BEST PRACTICE ?
               • ADMINISTRATOR CONFIGURE DESIRED ROOT BRIDGE WITH A LOWER PRIORITY
           • LOWER BRIDGE PRIORITY
             • IS PREFERABLE
           • 0 BRIDGE PRIORITY
             • PRECEDENCE OVER ALL OTHER BRIDGE PRIORITIES
           • LOWER VALUE BRIDGE ROOT
         • 2) EXTENDED SYSTEM ID (12 BITS )
           • DECIMAL VALUE ADDED TO BRIDGE PRIORITY
             • IDENTIFY VLAN FOR THIS BPDU
         • 3) MAC OF SWITCH ( 48 BITS )
           • LOWEST MAC SWITCH
           • USED ​​WHEN ?
             • SWITCHS SAME PRIORITY
             • SAME EXTENDED SYSTEM ID
       • NOTE : MESSAGE BPDU INCLUDES ROOT PATH COST
         • WHEN A SWITCH RECEIVES THE BPDU, IT INCLUDES THE SEGMENT GATEWAY COST TO DETERMINE THE INTERNAL ROOT PATH COST.