CCNA - Capitulo 9

CCNA - Capitulo 9

1. INTERNET LAYER

   • MAC E IP
     • DESTINATION SAME NETWORK
       • PHYSICAL ADDRESS
         • DIRECTLY
         • NIC TO NIC - SAME NETORK
       • LOGICAL ADDRESS
         • SAME NETWORK OR
         • REMOTE NETWORK
           • SEARCH ADDRESS GATEWAY
       • SEARCH THE ARP TABLE AND SEND DIRECLY
       • SEND THE ARP TABLE, DIDN'T FIND IT? DO THE ARP BROADCAST LOCAL SEGMENT
     • DESTINATION REMOTE NETWORK
       • SEND PACKET LOCAL DEFAULT GATEWAY
         • THE GATEWAY DECAPSULATES THE FRAME, ENCAPSULATES IT INTO A NEW FRAME, CHECKS THE ROUTING TABLE, AND FORWARDS THE PACKET.
         • OBS : IF THE ORIGIN DOES NOT KNOW THE MAC GATEWAY, THE ARP BROADCAT WILL BE MADE
       • SEARCH ARP TABLE DEFAULT GATEWAY AND SEND
       • SEND THE ARP TABLE, DIDN'T FIND IT? DO THE ARP BROADCAST LOCAL SEGMENT
     • PHYSICAL ADDRESS
       • DELIVER THE DATA LINK FRAME WITH THE ENCAPSULATED PACKET IP FROM NIC TO ANOTHER NIC
   • ADDRESS RESOLUTION PROTOCOL (IPV4)
     • ARP TABLE - CACHE ARP
       • COMMANDS
         • ROUTER# SHOW IP ARP
           • CISCO
           • TABLE
             • TIME STAMPED
         • ARP -A
           • WINDOWS
       • TEMPORARILY
         • HAVE NOT BEEN USED FOR A SPECIFIED PERIOD OF TIME ?
           • ARP CACHE REMOVES ARP
             • TIME DIFFER DEPENDNG ON OPERATING SYSTEM
         • MEMORY RAM
       • OBSERVAÇÃO
         • DYNAMICALLY CREATE
         • SWITCHES LAYER 2 DO NOT HAVE AN ARP TABLE
         • IT CAN ALSO BE CREATED STATICALLY.
     • ARP REQUEST
       • DESTINATION ADDRESS
         • FF-FF-FF-FF-FF-FF (BROADCAST)
           • THE SWITCH FORWARDS IT OUT ALL PORTS
             • EXCEPT THE INGRESS PORT.
           • ETHERNET NICS ON THE LAN TO ACCEPT AND PROCESS THE ARP REQUEST.
       • SOURCE ADDRESS
       • TYPE
         • 0x806
         • DATA PORTION OF THE FRAME NEEDS TO BE PASSED TO THE ARP PROCESS
       • WHEN WILL IT HAPPEN?
         • DOES NOT HAVE AN ENTRY FOR IPV4 IN ARP TABLE
     • ECHO REPLY
       • DESTINATION ADDRESS
         • ALWAYS UNICAST
       • SOURCE ADDRESS
         • UNICAST
       • TYPE
         • 0x806
           • DATA PORTION OF THE ETHERNET FRAME TO THE ARP PROCESS
           • UPPLER LAYER
       • IF NO DEVICE RESPONDS TO THE ARP REQUEST ?
         • THE PACKET IS DROPPED BECAUSE A FRAME CANNOT BE CREATED.tr
     • ARP ISSUES ?
       • ARP SPOOFING
         • HOW TO MITIGATE ?
           • DYNAMIC ARP INSPECTION (DAI)
         • FOR
           • ARP POISONING ATTACK
             • MAC WRONG
         • HOW DOES IT WORK?
           • 1 - THREAT ACTOR REPLY ARP REQUEST FOR IPV4 FOR ANOTHER DEVICE SUCH AS THE DEFAULT GATEWAY
       • ARP BROADCAST
         • LARGE NUMBER OF DEVICES TO BE POWERED UP AND ALL START ACCESSING NETWORKS SERVICES AT THE SAME TIME
           • NETWORK SLOW
     • WHATS IS THE PURPOSE OF ARP ?
       • RESOLVING IPV4 TO MAC
       • MANTAINING A TABLE IPV4 TO MAC MAPPING
         • ENTRIES IN THE ARP TABLE
           • TIMESTAMP
       • IDENTIFY THE HOST DESTINATION MAC AT LAYER 2 AND ALLOW THE ENCAPSULATED IP PACKET TO BE DELIVERED FROM ONE NIC TO ANOTHER WITHIN THE LOCAL NETWORK.
     • LAYER 3
     • FUNCTIONS ARP
       • WHEN PACKET IS SENT TO THE DATA LINK LAYER TO BE ENCAPSULATED INTO FRAME ,
         • DEVICE FIND TABLE IN THE MEMORY MAC MAPPED TO THE IP
       • SENDING DEVICE - SOURCE SEARCH ARP TABLE DESTINATION AND CORRESPONDING MAC
     • ARE ENCAPSULATED DIRETCLY WITHIN AN ETHERNET FRAME
   • NEIGHBOR DISCOVERY PROTOCOL ND , NDP
     • ICMPV6
     • 3 TYPES
       • ADDRESS RESOLUTION
         • NEIGHBOR SOLICITATION - NS
           • HOST A HOST
           • DESTINATION ADDRESS
             • MULTICAST
               • 33:33
         • NEIGHBOR ADVERTISEMENT - NA
           • HOST A HOST
         • DEVICE TO DEVICE (FF02::1)
         • USED FOR MAC ADDRESS RESOLUTION ; SIMILAR ARP REQUEST AND ARP REPLIES
       • REDIRECT MESSAGE
         • IS A REDIRECT MESSAGE WHICH IS USED FOR BETTER NEXT HOP SELECTION
       • SLAAC
         • ROUTER ADVERTISEMENT - RA
           • ROUTER A HOST
         • SOLICITATION ROUTER - RS
           • HOST A ROUTER
         • DEVICE TO ROUTER (FF02::2)
     • RFC 4861

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