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Carl0s81
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 Networking prep
Cabling, DataCenter, Hardware, Hubs, Network protocols, Networking, Routers, Switches, Tech support, Web services
Hiya guys, I have an interview next week, and in the pre screening phone interview a few questions came up about the port numbers used in networking and what they were used for, oh yeah, and the 7 layers of the OSI module. I Know a little bit of thew OSI, but is there any online papers etc, that could brush me up on these skills to help me out a bit? Thanks in advance, Carl.

Software/Hardware used:
ASKED: December 7, 2006  10:45 AM
UPDATED: December 12, 2006  7:46 AM
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Answer Wiki:
Below are some of the most common ports used. Ports are very flexible, the main thing is that both ends of the connection must be using the same ports at the same OSI layer in order for communication to happen. Telnet is typically 23, but if your server is set to recieve telnet on 9000 and you send it telnet on 9000, it will work. As far as a OSI layers, i found that www.networkdictionary.com has some insightful overviews. try this link http://www.networkdictionary.com/protocols/osimodel.php tcpmux 1 TCP, UDP TCP Port Service Multiplexer echo 7 TCP, UDP Echo discard 9 TCP, UDP Discard systat 11 TCP Active Users daytime 13 TCP, UDP Daytime (RFC 867) qotd 17 TCP Quote of the Day msp 18 TCP, UDP message send protocol chargen 19 TCP, UDP Character Generator ftp-data 20 TCP, UDP File transfer default data ftp 21 TCP, UDP File transfer control ssh 22 TCP, UDP Remote login protocol telnet 23 TCP, UDP Telnet smtp 25 TCP, UDP Simple Mail Transfer time 37 TCP, UDP Time rlp 39 TCP, UDP Resource location protocol nameserver 42 TCP, UDP Host name server whois 43 TCP, UDP Who is re-mail-ck 50 TCP, UDP Remote mail checking protocol domain 53 TCP, UDP Domain name server bootps 67 TCP, UDP Bootstrap protocol server bootpc 68 TCP, UDP Bootstrap protocol client tftp 69 TCP, UDP Trivial file transfer protocol gopher 70 TCP, UDP Gopher finger 79 TCP, UDP Finger www 80 TCP, UDP World wide web or HTTP kerberos 88 TCP, UDP Kerberos supdup 95 TCP, UDP SUPDUP hostname 101 TCP, UDP NIC Host Name Server iso-tsap 102 TCP, UDP ISO-TSAP Class 0 csnet-ns 105 TCP, UDP CCSO name server protocol rtelnet 107 TCP, UDP Remote Telnet Service pop-2 109 TCP, UDP Post Office Protocol - Version 2 pop-3 110 TCP, UDP Post Office Protocol - Version 3 sunrps 111 TCP, UDP SUN Remote Procedure Call auth 113 TCP, UDP Authentication Service sftp 115 TCP, UDP Simple File Transfer Protocol uucp-path 117 TCP, UDP UUCP Path Service nntp 119 TCP, UDP Network News Transfer Protocol nyp 123 TCP, UDP Network Time Protocol netbios-ne 137 TCP, UDP NETBIOS Name Service netbios-dgram 138 TCP, UDP NETBIOS Datagram Service netbios-ssn 139 TCP, UDP NETBIOS Session Service imap 143 TCP, UDP Internet Message Access Protocol snmp 161 TCP, UDP SNMP snmp-trap 162 TCP, UDP SNMPTRAP cmip-man 163 TCP, UDP CMIP/TCP Manager cmip-agent 164 TCP, UDP CMIP/TCP Agent xdmcp 177 TCP, UDP X Display Manager Control Protocol nextstep 178 TCP, UDP NextStep Window Server bgp 179 TCP, UDP Border Gateway Protocol prospero 191 TCP, UDP Prospero Directory Service irc 194 TCP, UDP Internet Relay Chat Protocol smux 199 TCP, UDP SMUX
Last Wiki Answer Submitted:  December 8, 2006  7:59 am  by  Gforsythe   75 pts.
All Answer Wiki Contributors:  Gforsythe   75 pts.
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Hi

Try http://compnetworking.about.com/cs/tcpportnumbers/

Gives a list of common port numbers and assignments

KasMcc
 230 pts.
 

The OSI model is indeed, a foundamental part of your overall IT knowledge base. You should begin to commit the various layers of the OSI model and its function and purpose to memory. You will be referring to it again and again throughout your IT career in one way or another.

I read once in a survey of IT professionals that the number one IT resource most often used is Google. There is plenty of information out there on the “OSI model” and “well-known ports”.

Get used to it. As an IT professional, you’ll be spending a lot of time researching, learning and teaching yourself much stuff using what many would arguably considered to be one of the greatest inventions we have ever created; The Internet.

Good luck on your interview.

SoftailRico
 0 pts.
 

Hi Carl,
I wanted to point out a few things we have on SearchNetworking.com that can help get you familiar with the OSI model:

Crash Course: OSI model
http://searchnetworking.techtarget.com/generic/0,295582,sid7_gci1147329,00.html

OSI reference guide
http://searchnetworking.techtarget.com/featuredTopic/0,290042,sid7_gci901109,00.html

Extending OSI to Network Security: Hack the Stack feature
http://searchnetworking.techtarget.com/general/0,295582,sid7_gci1226646,00.html

Kara Gattine, managing editor, SearchNetworking.com

SearchNetworkingEditorialTeam
 0 pts.
 

I would read some of the articles here, especially this one:
http://www.garykessler.net/library/tcpip.html

He does a really good job of tying the OSI and TCP stacks together so that you can get a better “real-world” understanding.

Kenton

Toneroo
 0 pts.
 

I would read some of the articles here, especially this one:
http://www.garykessler.net/library/tcpip.html

He does a really good job of tying the OSI and TCP stacks together so that you can get a better “real-world” understanding.

Kenton

Toneroo
 0 pts.
 

The best website to understand networking bacis would be

http://www.firewall.cx

Cheers,
Nitin

Nitint
 0 pts.
 

Another great resource is Wikipedia. I find myself referring people to it who need basic, foundational type knowledge as it includes a lot of history which helps you put things in context. Also, about every third word is a link to its definition.

Jspainhour
 0 pts.
 

for interviews:
Ports to stick to:
Port # Common Service Port # Common Service
Protocol Protocol
20 TCP ftp-control 80 TCP http
21 TCP ftp-data 110 TCP pop3
23 TCP telnet 161 UDP snmp
25 TCP smtp 162 UDP snmp-trap
53 TCP/UDP dns 443 TCP https(http/ssl)
69 UDP tftp
70 TCP gopher 1080 TCP socks
79 TCP finger 33434 UDP traceroute

Memorise these above ports.
Secondly..
http://www.windowsecurity.com/img/upl/osi_layers.gif
has a three columned approach. The OSI layer is one of the ways of expressing levels of inter system communication.
TCP/IP is another approach and LAN is another.

Mnemonically:
Please Do Not Test Senior Project Administrators.
Physical/Data/Network/Transport/Session/Presentation/Application

Enterprisephil
 0 pts.