1. connectionless does not do acknowledgement, if lower layer uses connectionless protocols
* upper layer take care of the connection

2. network layer addressing: IP
* is hierarchical, allows broadcast, contains network and host portion

3. Which type of media is immune to EMI and RFI
* non-electrical-magnetic signals --> optics

4. nslookup
* shows the current DNS server

5. mail system
* MUA	U:user
* MTA	T:transmit
* MDA	D:deliver
* SMTP	sending mail
* POP	receiving mail (last mile)

6. proxy ARP
* host: .50/26		.33/27 router .1/27		destination: .20/27 

7.  host --- sw .2/28 --- .1/28 router
* what can be host's ip, subnet mask and default gateway?
Ans: x.x.x.y 255.255.255.240 x.x.x.1  2<y<15

8. CSMA/CD
* all units see data on the medium
* listen before talk --> detect busy signal
* listen while talking --> detect jam signal
* back-off

9. private network (RFC1918)
* 10.0.0.0/8
* 172.16.0.0/12
* 192.168.0.0/16

10. router configuration
* enable secret
* enable password
* line vty 0 4
	login
	password
* clock rate --> DCE

11. Which three IPv4 addresses represent a broadcast for a subnet? (Choose three.)
	192.168.4.63 /26
	192.168.4.129 /26
	192.168.4.191 /26
	192.168.4.51 /27
	192.168.4.95 /27
	192.168.4.221 /27 
/27 ==> H= 32-27 = 5
2^5=32 size, increment, range
0,32,64,96,128,160,192,224
256/32=8

/26 ==> H= 32-26 = 6
2^6=64 range
0,64,128,192

12. NAT <---> Internet

13. During the encapsulation process, which identifiers are added at the transport layer?
	two networks routing the packets
	two applications communicating the data
	two hosts at either end of the communication
	two nodes on the local network exchanging the frame 

14. A---R1-----R2-----B
* dest IP: B
* next hop MAC: R1 left interface

15. sh ip route
* connected

16. #copy run start  (wr)

17. well known service port number
* 0-1023
* 21,23,25,53,67,69,80,110,139,143,443
* FTP,telnet,SMTP,DNS,DHCP,tftp,http,POP,netBIOS,IMAP,https

18. Cisco Router
* Flash - IOS
* ROM - POST, partial IOS
* NVRAM - startup-configuration
* RAM - working area

19. hub-hub-sw-hub-sw-sw-sw, router
* collision domain
* broadcast domain
* subnets

20. traceroute/tracert
* TTL

21. administratively down
* no shutdown to change it to up