CCNA 3 - Capitulo 2.4

CCNA 3 - Capitulo 2.4

1. SINGLE AREA OSPFv2 CONFIGURATION

   • MODIFY SINGLE AREA OSPFV2
     • HELLO PACKETS - INTERVALS
       • WHATS IS DEAD INTERVAL ?
         • PERIOD THAT THE ROUTER WAITS TO RECEIVE A HELLO PACKET
         • HOW MODIFY OSPFV2 INTERVALS ?
           • R1(CONFIG-IF)# IP OSPF HELLO-INTERVALS SECONDS
           • R1(CONFIG-IF)# IP OSPF DEAD-INTERVALS
         • CISCO DEFAULT
           • HOW VIEW DEAD TIME COUTING ?
             • R1#SHOW IP OSPF NEIGHBOR
           • HOW IS IT CALCULATED ?
             • 4X INTERVALS HELLO = 4X10 = 40
         • WAITS TO RECEIVE A HELLO PACKET BEFORE DECLARING THE NEIGHBOR DOWN
         • OSPF REMOVES THAT NEIGHBOR FROM ITS LINK STATE DATABASE (LSDB)
           • AND THE ROUTER FLOOS THE LSDB WITH INFORMATION ABOUT THE DOWN FOR OSPF ENABLED INTERFACES
       • VERIFY HELLO AN DEAD INTERVALS ?
         • R1#SHOW IP OSPF INTERFACE G0/0/0
       • HELLO PACKETS ARE TRANSMITTED TO MULTICAST ADDRESS 224.0.0.5 (ALL OSPF ROUTERS )
         • EVERY 10 SECONDS - IS DEFAULT VALUE ON MULTIACCESS AND POINT TO POINT NETWORKS
       • INTERVAS HELLO AND DEAD MUST MATCH OR A NEIGHBOR DOES NOT OCCUR
       • CAUTION ? NBMA NETWOKS THE DEFAULT HELLO IS 30 SECONDS
     • ADJUST THE REFERENCE ABDNWIDTH
       • THE COST VALUE MUST BE AN INTEGER
       • CHANGING THE REFERENCE BANDWIDTH
         • DOES NOT ACTUALLY AFFECT THE BANDWIDTH CAPACITY ON THE LINK
         • IT SIMPLY AFFECTS THE CALCULATION USED TO DETERMINE THE METRIC
         • HOW TO CHANGE ?
           • 2. R1(CONFIG)# AUTO-COST REFERENCE-BANDWIDTH 100 1000 10000
             • MUST BE CONFIGURED ON EVERY ROUTER IN THE OSPF DOMAIN
             • VALUE IS EXPRESSED IN Mbps
         • HOW TO VIEW?
           • R1# SHOW IP OSPF INTERFACE GIG 0/0/0
       • ALL INTERFACES FASTER THAN WILL HAVE THE SAME COST VALUE OF 1 AS FAST ETHERNET INTERFACE
         • THE REFERENCE SHOULD BE ADJUSTED ANYTIE THERE ARE LIKS FAST THAN FASTeTHERNET (100Mbps)
     • OSPF ACCUMULATES COST
       • THE COST OF AN OSPF IS THE ACCUMULATED VALUE FROM ONE ROUTER TO THE DESTINATION
       • THE LOOPBACK INTERFACES HAVE A DEFUALT COST OF 1
       • HOW TO VIEW ?
         • R1#SHOW IP ROUTE | INCLUDE 10.10.2.0
     • CISCO OSPF COST METRIC
       • ROUTING PROTOCOL USES A METRIC TO DETERMINE TO BEST PATH
       • A METRIC INDICATE OVERHEAD TO SEND PACKET ACROSS A CERTAIN INTERFACE
       • OSPF USES COST AS A METRIC
         • LOWER COST = BETTER PATH
       • THE CISCO COST IS INVERSELY PROPORTIONAL TO THE BANDWIDTH OF THE INTERFACE
         • HIGHER BANDWIDTH = LOWER COST
       • COST INTERFACE SHARE THE SAME COST ? TO CORRET THIS SITUATION YOU CAN
         • ADJUST THE REFERENCE BANDWIDTH WITH THE
           • 1. R1(CONFIG)# ROUTER OSPF 10
           • 2. R1(CONFIG)# AUTO-COST REFERENCE-BANDWIDTH
         • MANUALLY SET OSPF COST NECESSARY INTERFACES
           • 1. R1(CONFIG-IF)# IP OSPF COST
     • MANUALLY SET OSPF COST VALUE
       • 1. IF THE OSPF COSTS FOR A DESTINATION NETWORK ARE EQUAL, THE TRAFFIC WILL BE BALANCED.
         • COST VALUE CAN BE MANIPULATED TO CREATE A BACKUP ROUTE
       • OR
       • 2. OTHER VENDOR MAY CALCULATE OSPF IN A DIFFERENT MANNER
       • HOW TO CONFIGURE ?
         • R1(CONFIG)# INTERFACE G0/0/1
         • R1(CONFIG-IF)#IP OSPF COST 30
         • R1(CONFIG)I#NTERFACE LO0
         • R1(CONFIG-IF)#IP OSPF COST 10
     • TEST FAILOVER TO BACKUP ROUTE
       • DISABLE THE MAIN LINK AND CHECK IF A FAILOVER OCCURS.
     • MODIFY OSPFv2 INTERVALs
       • THEY CAN BE MODIFIED FOR DETECT FAILURES IN LESS TIME
         • ONLY BE ALTERED IN RARE SITUATIONS
       • MODE COMMANDS
         • R1(CONFIG-IF)# IP OSPF HELLO-INTERVAL seconds
         • R1(CONFIG-IF)# IP OSPF DEAD-INTERVAL seconds