Tag Archives: ICND1

AJSnetworking.com Book Giveaway – ICND1

CCENT

I will be giving away my tech book collection here at the blog throughout the month as a thank you to my readers!

First up – the top-rated Odom text for ICND1 (CCENT):

ICND1

The first reader THAT TRULY NEEDS this book for their studies to respond using the Contact Anthony link at the top of the blog will receive it. You must meet these conditions:

  • Mailing address in the continental US
  • Provide valid full name and mailing address in the email
  • Be a good person 🙂

I am so glad I can help you in your studies!

Are You Smarter Than a CCENT? Transport Layer

CCENT, , , , ,

Here is a query from a current project – enjoy!

  1. You are examining a packet capture from your local network. What two determinations can you make from this output? (Choose 2)

100-105a. This is a UDP packet
b. This is a TCP packet
c. The target destination is FTP
d. The target destination is HTTP

Correct Answer: b, d

Explanation: Due to its use of reliable transmissions, Transmission Control Protocol (TCP) uses many fields in its packet structure. These include:

  • source TCP port number
  • destination TCP port number
  • sequence number
  • acknowledgement number
  • TCP data offset
  • reserved data
  • control flags
  • window size
  • TCP checksum
  • urgent pointer
  • TCP optional data

In contrast, the unreliable User Datagram Protocol (UDP) packets feature these simple fields:

  • source port number
  • destination port number
  • length
  • checksum

From the destination TCP port number here of 80, you can determine the intended target service is the Hypertext Transfer Protocol (HTTP). Know the following common ports for this exam:

Port Number TCP or UDP Protocol
20 TCP FTP Data
21 TCP FTP Control
22 TCP SSH
23 TCP Telnet
25 TCP SMTP
53 UDP DNS
67, 68 UDP DHCP
69 UDP TFTP
80 TCP HTTP
110 TCP POP3
161 UDP SNMP
443 TCP SSL/TLS
514 UDP Syslog
520 UDP RIP