Chapter VI, Internet technology
Test sites 1, IP address classification
Test method [analysis]
This test method is a test center substantially investigate A, to distinguish between B, C, D of the four IP address, public address, and to distinguish the private network address, the address can be done and what the source address, destination address which addresses can be done
Points [analysis]
1, Class A addresses the first byte range is 1-126, a first class B address range is 128-191 bytes, the first byte of a Class C address range is 192-223, Class D multicast address of a byte range is 224-239. The multicast address test more often
2, the scope of the private network addresses:
A private network address class network number: 10
Class B private network address network number: 127.16-127.31
Class C network number private network address: 192.168.0-192.168.255
3, host address, loopback address (beginning 127) and Microsoft addresses (169.254) can be used as source and destination addresses
0.0.0.0 can do source address, destination address can not be done
Broadcast address can do the destination address, source address can not be done
Remarks [coaching]
Memory knowledge points to keep in mind
2 test sites, subnetting
Test method [analysis]
This test center is given a basic test method IP network segment, and proposed how many subnets need to be divided, the number of hosts per subnet needs, seeking to make a valid IP address or subnet mask for each subnet range of each subnet
Points [analysis]
1, IP addresses have a network and host bits
2, need to borrow bit network to the host bits for subnetting
3, to borrow the N-bit host bits, it is divided by 2N subnets
4, the host bits remaining M bits, the number of valid IP address for each subnet is 2M-2 th
Remarks [coaching]
Computational knowledge, p3, it is recommended to master the problem by doing method, the mastery approach is to send sub-themes
Test sites 3, CIDR
Test method [analysis]
This test method is a test center gives substantially more IP segments, and then aggregated into one IP network segment
Points [analysis]
1, can be understood as the inverse of subnetting
2, the title to the IP address expanded into binary form
3. Expand the IP address, look exactly the same as a binary number in which bits are part of, part of it is exactly the same as the network place, not the same place it as the host site
4, after the thumbnail may be aggregated into an IP network segment
Remarks [coaching]
Computational knowledge, p3, it is recommended to master the problem by doing method, the mastery approach is to send sub-themes
Test sites 4, IP datagrams
Test method [analysis]
This test method is the basic test sites know to understand the meaning of the minimum length of the IP datagram header and the header of each field
Points [analysis]
1, the IP datagram header length is 20 bytes minimum, its value in the header length field of 5
2, often test fields are as follows:
ID: A unique identification number for identifying a packet or a packet of slices
Fragment Offset: If the packet is fragmented, the sheets may be offset by the data packets of the fragments assembled
Flag: a data packet is part of a packet of slices.
Remarks [coaching]
Memory of knowledge, we can understand
Test sites 5, ARP
Test method [analysis]
This test method is the basic test sites know to understand the concept of ARP
Points [analysis]
1, ARP is a protocol to obtain the corresponding IP address mac address
2, by a broadcast query requesting party, asking mac address corresponding to the IP address. The inquiring party to respond to your mac address by unicast
3, know view and clear arp cache command
Remarks [coaching]
Memory of knowledge, need to know
Test sites 6, ICMP
Test method [analysis]
This test method is the basic test sites know to understand the concept of ICMP
Points [analysis]
1, the role of ICMP error warning is sent to a transmission source host
2, ICMP IP encapsulation is
3, the two applications is the ICMP ping and tracert (traceroute), ping and using the response to the ICMP echo request packet is, tracert use time exceeds ICMP Destination Unreachable packets and packets
Remarks [coaching]
Memory of knowledge, need to know
Test sites 7, IPv6
Test method [analysis]
This test method is basically the test center know understand the basics of IPv6, IPv6 addresses as correct wording, we can distinguish between different types of addresses, and IPv4 to IPv6 transition technology
Points [analysis]
1, IPv6 is to solve the problem of not enough IPv4 addresses, IPv6 has 128-bit
2, IPv6 address as a group 16, group 8, in hexadecimal notation. One or more leading zeros hexadecimal digits from any group is deleted; typically all or all of leading zeros for this operation. For example, 0042 is converted into 42 groups. Zero continuous portion (a double-colon: :) replaced. Double colon can only be used once in the address
3、
| Address Type |
Address prefix |
IPv6 prefix identifies |
| Link-local addresses |
1111111010 |
FE80::/10 |
| Site-local addresses |
1111111011 |
FEC0::/10 |
| Global unicast address |
Global Routing Prefix (48bit), the former three fixed at 001 |
|
4, transition technologies: dual stack, tunneling, Network Address Translation (otherwise known as translation technology)
Remarks [coaching]
Memory of knowledge, need to know
8 test sites, UDP and TCP transport layer protocol
Test method [analysis]
This test center is the basic test method can distinguish between UDP and TCP protocols, understand the meaning of each field in the TCP header, three-way handshake to understand the process, know the port number used by common applications
Points [analysis]
1, UDP is a connectionless protocol unreliable, TCP is a reliable transport layer protocol link
2, TCP header length is 20 bytes minimum
3, TCP header fields common meanings:
ID: indicates a TCP segment with this number
No acknowledgment: a confirmation response to the other, while this figure is desirable from a communication packet to another device serial number obtained
URG: urgent pointer bits
ACK: acknowledgment number bits
RST: reconnection or refuse a connection is invalid
SYN: request to establish a connection flag
FIN: close a connection request
Window: means receiving window size of the buffer represented
Urgent Pointer: If the URG bit is set, this field will be checked as additional instruction, tells the CPU where data is read
4, three-way handshake packet characteristics: first and second SYN packet will be a sign
1, know the common application protocol port number (will be mentioned later in the application layer knowledge points)
Remarks [coaching]
Memory of knowledge, need to know
9 test sites, Domain Name System (DNS)
Test method [analysis]
This test center to test the basic law is familiar with the concept of the DNS: If the DNS query sequence, iterative queries and recursive queries meaning the difference between the representation and resource records
Points [analysis]
1, DNS uses UDP port 53
2, DNS query sequence: In the client, first check the hosts table, and then check the cache. Finally, the dns queries. In the server, first check the cache, and then check the area record, if can not find, then go to the root name server queries
3, recursive query: when the server receives a query request, to return a corresponding result directly. Iterative query: When the server receives a query request can not return the results directly, but to the inquiring party to find another server to search.
4 for the common resource records, such as host (A) record, pointer (PTR) records, alias (CNAME) record
Remarks [coaching]
Memory of knowledge, need to know
10 test sites, remote login service TELNET
Test method [analysis]
This basic test sites test to know if the transmission format used by the port number and use Telnet
Points [analysis]
1, Telnet using TCP port 23
2, the transmission format used NVT
Remarks [coaching]
Memory of knowledge, we can understand
11 test sites, FTP file transfer service
Test method [analysis]
This test center is to understand the basic test method FTP port number used to distinguish between active and passive mode of FTP
Points [analysis]
1, FTP in the active mode, the control connection port 21, the data connection using a 20-port
2, FTP in the passive mode, a control connection port 21, the data connection using any of a port 1024-65535
3, on the afternoon exam, no special note is the use of data connection ports but only that port, then select port 21
Remarks [coaching]
Memory of knowledge, need to know
12 test sites, Dynamic Host Configuration Protocol DHCP
Test method [analysis]
This test center to test the basic law is known to use DHCP port, DHCP allocation process used in four packets and DHCP relay principle
Points [analysis]
1, DHCP servers use UDP port 67, the client uses UDP port number 68
2, when using the DHCP protocol, if the client can obtain the IP address and other parameters. Description DHCPdiscover, DHCPoffer, DHCPrequest, DHCPack four successful exchange packets
3, DHCPdiscover and DHCPrequest message sent by the client are broadcast packets. The server sends the DHCPoffer and DHCPack message may be unicast message may also be broadcast packet, if the title is asked to use unicast or broadcast, it is recommended to select broadcast.
4, Windows server configuration DHCP, the default lease is eight days, the default lease Huawei router 1 day
5, for dynamic host configuration, each segment plus a dhcp server, is unrealistic. DHCP relay can be used to achieve a dhcp server configured to assign a plurality of subnets.
Since the purpose of ip DHCP packet is 255.255.255.255, such as local broadcast can not cross subnets. This requires the DHCP relay gateway on the client, then the default gateway can convert the broadcast packets so as to be transmitted across the network unicast packets.
Remarks [coaching]
Memory of knowledge, need to know
13 test sites, e-mail service
Test method [analysis]
Port used in this test sites basic test method is known email service application layer protocol used, and the corresponding protocol
Points [analysis]
1, in the case where the user agent, the sending user sends mail to the mail server, and sending mail server to the SMTP protocol is used by the recipient mail server, SMTP protocol uses port numbers TCP25. When the recipient user receives the mail from the server to acquire the message, using the POP3 protocol, port TCP110 using POP3 protocol.
2, if a user using a web send and receive messages. The sender sends the mail to the mail server and the receiving side getting mail from the mail server, the HTTP protocol is used, port 80 using the HTTP protocol. And establish a connection between the server still uses the SMTP protocol.
3, traditional e-mail can only handle text format, data type that can be sent by e-mail but now has been extended to MIME, supports images, video, audio, and other forms of data.
Remarks [coaching]
Memory of knowledge, need to know