Cisco CCNA exam Cram Sheet General Networking Port Numbers Port Number Layer 4 Protocol Suite Application 20 TCP FTP Data 21 TCP FTP Program 23 TCP Telnet 25 TCP SMTP 53 TCP/UDP DNS 69 UDP TFTP 80 TCP HTTP Ping Responses ! – Reply from target address . – Timeout U – Destination unreachable C – Congestion experienced I – User interrupt ? – Unknown packet type & – Packet lifetime exceeded Ethernet 5-4-3 rule – Between any 2 nodes there can only be a maximum of 5 segments, 4 repeaters and only 3 of those segments can have hosts. Loop back address – 127.0.0.1, tests

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