Shulou(Shulou.com)06/01 Report--

① turns the Windows feature on or off:

Control Panel-programs-turn Windows on or off

② TFTP and FTP

TFTP is a simple protocol for transferring files, which is implemented in the UDP protocol, but we are not sure that some TFTP protocols are based on other transport protocols. This protocol is designed for small file transfer. Therefore, it does not have many of the usual functions of FTP, it can only obtain or write files from the file server, cannot list directories, does not authenticate, it transmits 8-bit data. There are three modes in the transfer: netascii, which is the 8-bit ASCII code, and octet, which is the 8-bit source data type; the last mail is no longer supported and returns the returned data directly to the user rather than saving it as a file.

③ LACP Link aggregation Control Protocol

LACP, LACP (Link Aggregation Control Protocol, Link aggregation Control Protocol) based on IEEE802.3ad standard, is a protocol to realize dynamic aggregation of links. The LACP protocol exchanges information with the peer through LACPDU (Link Aggregation Control Protocol Data Unit, link aggregation control protocol data unit).

Simple name

LACP

Working mode

Passive,active

Use occasion

A situation where bandwidth is tight.

Catalogue

1 Overview

2 static aggregation

3 dynamic convergence

4 working mode

5 occasions for use

Overview of LACP

Editing

When the LACP protocol for a port is enabled, the port advertises its system priority, system MAC address, port priority, port number, and operation Key to the peer by sending LACPDU. After receiving the information, the peer compares the information with the information saved by other ports to select the port that can be converged, so that the two sides can agree on whether the port can join or exit a dynamic aggregation group.

Operation Key is a configuration combination generated by LACP protocol according to port configuration (i.e. rate, duplex, basic configuration, management Key) when a port is trunked.

When the LACP protocol is enabled, the management Key of the dynamic trunk port defaults to zero. Static trunk port when LACP is enabled, the management Key of the port is the same as the aggregation group ID.

For dynamic aggregation groups, members of the same group must have the same operation Key, while in manual and static aggregation groups, ports in Active have the same operation Key.

Port trunking is the aggregation of multiple ports together to form an aggregation group to achieve the sharing of output / input load among the member ports in the aggregation group, and also provides higher connection reliability.

LACP static aggregation

Editing

1. Static lacp trunking is manually configured by the user and does not allow the system to automatically add or remove ports from the aggregation group. There must be at least one port in the aggregation group. When an aggregation group has only one port, the port can only be deleted from the aggregation group by deleting the aggregation group.

The lacp protocol of the static trunk port is activated. When a static aggregation group is deleted, its member ports will form one or more dynamic lacp trunks and keep the lacp active. The lacp protocol that prevents users from shutting down static trunking ports.

two。 Port status in static aggregation group

In a static aggregation group, the port may be in two states: selected or standby. Both selected port and standby port can send and receive lacp protocol, but standby port cannot forward user messages.

In a static aggregation group, the system sets the port to the selected or standby state according to the following principles:

According to the priority of port full-duplex / high-speed, full-duplex / low-speed, half-duplex / high-speed, half-duplex / low-rate, the system chooses the port with the highest priority in the selected state, and the other ports in the standby state.

Different from the peer device connected to the smallest port in the selected state, or the port connected to the same peer device but the port in a different aggregation group will be in the standby state.

Ports cannot be trunked together due to hardware limitations (such as not being able to truncate across boards), and ports that cannot be trunked with the smallest port in the selected state will be in the standby state.

Ports that are different from the basic configuration of the smallest port in the selected state will be in the standby state.

Due to the limit of the number of selected ports in the aggregation group that the device can support, if the current number of member ports exceeds the maximum number of selected ports that the device can support, the system will select some ports as selected ports and others as standby ports according to the port number from smallest to largest.

LACP dynamic aggregation

Editing

1. Overview of dynamic lacp aggregation

Dynamic lacp aggregation is a kind of aggregation created / deleted automatically by the system, which does not allow users to add or delete member ports in dynamic lacp aggregation. Only ports with the same speed and duplex attributes, connected to the same device, and the same basic configuration can be dynamically aggregated together. Dynamic trunking can be created even if there is only one port, which is a single-port trunking. In dynamic trunking, the lacp protocol of the port is enabled.

two。 Port status in a dynamic aggregation group

In a dynamic aggregation group, a port may be in two states: selected or standby. Both selected port and standby port can send and receive lacp protocol, but standby port cannot forward user messages.

Due to the limit of the maximum number of ports in the aggregation group that the device can support, if the current number of member ports exceeds the limit of the maximum number of ports, the local system and the peer system will negotiate and determine the status of the port according to the size of the port id at the superior end of the device id. The specific negotiation steps are as follows:

Compare device id (system priority + system mac address). Compare the system priority first, and then compare the system mac address if the same. The small end of the device id is considered to be superior.

Compare port id (port priority + port number). For each port on the preferred side of the device id, first compare the port priority, and then compare the port number if the priority is the same. Port id small ports are selected ports, and the remaining ports are standby ports.

In an aggregation group, the port in the selected state with the lowest port number is the primary port of the aggregation group, and the other ports in the selected state are member ports of the aggregation group.

LACP working mode

Editing

The port that starts LACP can operate in two modes, passive, and active. [1]

Passive: passive mode, in which the port does not actively send LACPDU messages. After receiving the LACP messages sent by the peer, the port enters the protocol computing state.

Active: active mode, in which the port will actively send LACPDU messages to the peer to calculate the LACP protocol.

LACP usage occasion

Editing

1) when the bandwidth is tight, the bandwidth can be extended to n times that of the original link through logical aggregation.

2) in the case of dynamic backup of links, you can configure link aggregation to achieve dynamic backup among the member ports of the same aggregation group.

④ Gateway

Forward data from different network segments

⑤ transfer

Data transfer: there is no return

Route delivery: go and go back

⑥ black hole routing

When summarizing, misvisits will occur if the summary address contains a network segment that does not exist in the actual network. So that they have no return routes, which are not in the actual route summary table.

⑦ Multicast address

Multicast address

In order to enable the multicast source to communicate with the multicast group members, it is necessary to provide network layer multicast and use the IP multicast address. In order to

To achieve the correct transmission of multicast information on the local physical network, it is necessary to provide link layer multicast and use multicast MAC addresses. Must

There is a technique for mapping IP multicast addresses to multicast MAC addresses.

IPv4 Multicast address

IANA (Internet Assigned Numbers Authority, Internet numbering Committee) divides class D address space

It is allocated to IPv4 multicast. The total number of IPv4 addresses is 32 bits, and the highest 4 bits of class D addresses is 1110, so the address range is 224.0.0.0.

To 239.255.255.255, the specific classification and meaning are shown in Table 1-1-2.

Table 1-1-2 range and meaning of IPv4 Multicast addresses

Meaning of address range

224.0.0.00224.0.0.255 permanent group address. The IP address reserved by IANA for the routing protocol (also known as the reserved group site)

Address), used to identify a specific set of network devices for routing protocols, topology lookups, etc.

Used, not for multicast forwarding. Common permanent group addresses are shown in Table 1-1-2.

224.0.1.0 to 231.255.255.255

233.0.0.05238.255.255.255

ASM Multicast address, valid network-wide

232.0.0.00232.255.255.255 default SSM Multicast address, valid network-wide

239.0.0.0" 239.255.255.255 local administrative group address, valid only within the local administrative domain. Heavy in different administrative domains

Reusing the same local administrative group address will not lead to conflict

Permanent group address meaning HCIE-R&S preparation materials

8

224.0.0.0 No allocation

All hosts and routers in the 224.0.0.1 network segment (equivalent to broadcast address)

224.0.0.2 all Multicast routers

224.0.0.3 No allocation

224.0.0.4 DVMRP (Distance Vector Multicast Routing Protocol, distance vector group

Broadcast routing Protocol) Router

224.0.0.5 OSPF (Open Shortest Path First, Open shortest path first) Router

224.0.0.6 OSPF DR (Designated Router, designated router)

224.0.0.7 ST (Shared Tree, shared Tree) Router

224.0.0.8 ST host

224.0.0.9 RIP-2 (Routing Information Protocol version 2, routing Information Protocol version

2) Router

224.0.0.11 Mobile Agent (Mobile-Agents)

224.0.0.12 DHCP (Dynamic Host Configuration Protocol, dynamic Host configuration Protocol)

Server / Relay Agent

224.0.0.13 all PIM (Protocol Independent Multicast, Protocol Independent Multicast) routers

224.0.0.14 RSVP (Resource Reservation Protocol, Resource reservation Protocol) encapsulation

224.0.0.15 all CBT (Core-Based Tree, Kernel Tree) routers

224.0.0.16 specify SBM (Subnetwork Bandwidth Management, subnet bandwidth management)

224.0.0.17 all SBM

224.0.0.18 VRRP (Virtual Router Redundancy Protocol, Virtual Router redundancy Protocol)

224.0.0.22 all enable IGMPv3 (Internet Group Management Protocol, Version 3

Internet group management protocol) router

224.0.0.19 ~ 224.0.0.21

224.0.23 ~ 224.0.0.255

Not specified

eight

Characteristics of VTY in H3C

The user interface view also includes: AUX user interface view, TTY (entity type terminal) user interface view, VTY (virtual type) user interface view. So for VTY view, each device can support multiple VTY users to access at the same time

⑨ neighbor relationship: only neighbor relationship has been established

Adjacency: establish a data connection so that data can be accessed each other

Status of OSPF adjacency

1.Down: no information has been exchanged with other routers in this state. The hello packet is first sent out its ospf interface, and the DR (in the case of a broadcast network) or any other router is not known. The multicast address 224.0.0.5 is used to send hello packets.

2.Attempt: only suitable for NBMA networks, where neighbors are manually specified in NBMA networks, the router will use HelloInterval instead of PollInterval to send Hello packets.

3.Init: indicates that a Hello packet has been received in DeadInterval, but 2-Way communication is still not established.

4.two-way: two-way session establishment, while RID appears in each other's neighbor list. (if it is a broadcast network: for example: Ethernet. DR,BDR should be elected at this time. )

5.ExStart: the initial state of information exchange, in which the local router and its neighbors will establish a Master/Slave relationship and determine the DD Sequence Number. The large ID of the router becomes Master.

6.Exchange: information exchange status in which one or more DBD packets (also known as DDP) are exchanged between the local router and its neighbors. DBD contains summary information about LSA entries in LSDB).

7.Loading: message loading status: after receiving the DBD, compare the received information with the information in the LSDB. If there is an updated link-state entry in the DBD, a LSR is sent to the other party to request a new LSA.

8.Full: full adjacency state, and the link-state database synchronization between neighbors is completed, which is judged by the fact that the neighbor link-state request list is empty and the neighbor state is Loading.

10.

Seven states of OSPF (neighbor and adjacency)

1 Down status-in the Down state, the OSPF process has not exchanged information with any neighbors. OSPF is waiting to enter the Init state.

2 Init status-OSPF routers send type 1 (Hello) packets at regular intervals (the default is 10s) to establish a special relationship with neighboring routers.

3 Two-Way (bidirectional) state-each OSPF router uses packets to attempt to establish bidirectional state or bidirectional communication with all neighboring routers in the same IP network. The Hello packet contains a list of OSPF neighbors known to the sender. When a router sees itself in an Hello packet of a neighboring router, it enters a two-way state.

4 ExStart (quasi-start) state-when the router and its neighbors enter the ExStart state, the conversation between them is characterized as an adjacency, but the router has not yet become a full adjacency state. ExStart state is established using type 2 database description (DBD,DataBase Description) packets, and two routers use Hello packets to negotiate the relationship between them who is "master" and who is "slave". (the router with the highest OSPF router ID will win and become the "master")

5 Exchange (switching) state-in the switched state, neighboring routers use type 2 DBD packets to send their link-state information to each other, that is, routers describe their link-state databases to each other. Routers compare what they have learned with their existing link-state database and individually acknowledge each DBD packet. If any router receives link information that is not in its database, the router requests complete update information about the link from its neighbors. The complete routing information is exchanged in the "Loading" state.

6 Loading (load) status-after describing each other's respective link-state databases, routers can request more complete information with a type 3 link-state request (LSR) packet. When a router receives a LSR, it responds with a link-state update (LSU) packet of type 4. These type 4 LSU packets contain the exact LSA, while LSA is the core of the link-state routing protocol, and type 4 LSU packets are recognized by type 5 packets.

7 Full Adjacency (full adjacency) state-after the loading state ends, the router enters the full adjacency state. Each router keeps a list of adjacent routers, which is called the adjacent database.

eleven

What factors affect the neighbor relationship or adjacency of OSPF? (OSPF marks the success of establishing a neighbor relationship)

1. Router-ID is different.

2. Hello time must be the same.

3. Dead time must be the same.

4. The region ID must be the same

5. Authentication must be the same.

6. The LSA support bits in the Option field must be the same (special area)

7. MTU mismatch cannot form an adjacency (EXSTART on one side and EXCHANGE on the other)

8. OSPF version number is different (currently version 2)

9. When the OSPF network type is MA, the mask must be the same (two neighbors). Unable to describe the network segment because DR and LSA-2 will appear

twelve

RIPv1 and RIPv2. Main differences of RIPv1

RIPv1 and RIPv2. The main differences of RIPv1:

1.RIPv1 is a classful routing protocol and RIPv2 is a classless routing protocol.

2.RIPv1 cannot support VLSM,RIPv2 can support VLSM

3.RIPv1 does not have the function of authentication, RIPv2 can support authentication, and there are both plaintext and MD5 authentication

4.RIPv1 does not have the function of manual summarization. RIPv2 can do manual summarization on the premise of turning off automatic summarization.

5.RIPv1 is a broadcast update and RIPv2 is a multicast update

6.RIPv1 does not tag routes. RIPv2 can mark routes (tag) for filtering and policy.

The updata sent by 7.RIPv1 can carry a maximum of 25 route entries, and RIPv2 can only carry a maximum of 24 routes with authentication.

There is no next-hop attribute in the updata packet sent by 8.RIPv1. RIPv2 has a next-hop attribute, which can be reset with routing updates.

thirteen

The MAC address is a 48-bit binary number, usually represented by a 12-bit hexadecimal number

It can be understood that the binary system can tell the true from the false mac really, that is, the only fake is the software modified, the hexadecimal representation, the first half indicates the manufacturer, the back is marked, maybe my expression is not entirely correct, take a look at Baidu, the explanation of those magical people

fourteen

IP

Explanation of IP address and Subnetting

Author: Li Shixin

IP address

Brief introduction

IP addresses are divided into five categories:

Class A for large networks (126networks, 1677214 hosts) Class B for medium-sized networks (16384 networks, 65534 hosts) Class C for small networks (2097152 networks, 254hosts) Class D for Multicast (sending of multi-destination addresses) Class E for experiments

In addition, the all-zero (0.0.0.0.) address refers to any network. The all-1 IP address (255.255.255.255) is the broadcast address for the current subnet.

In the Internet, each connection of each computer has a number assigned by the authorized unit to distinguish it from each other, that is, the IP address. The IP address adopts a hierarchical structure and is divided into two parts according to the logical structure: the network number and the host number. The network number is used to identify a logical network, while the host number is used to identify a connection of a host in the network. Therefore, the addressing method of the IP address carries an obvious location message.

A complete IP address consists of 32 bytes, or 32-bit digits. In order to facilitate users' understanding and memory, dotted decimal notation is used with symbols in the middle. Separate different bytes.

For example, the IP address in 32-bit form is as follows: 00001010 00000000 00000000 00000001 in decimal form as follows: 10.0.0.1

Class An address

(1) Class An IP address. By 1 byte network address and 3 byte host address, the network

The highest bit of the address must be "0".

For example: 0XXXXXXX.XXXXXXXX.XXXXXXXX.XXXXXXXX (X stands for 0 or 1)

(2) Class An IP address range: 1.0.0.1 Murray 126.255.255.254 (3) Private address and reserved address in Class An IP address: ① 10.X.X.X is a private address (the so-called private address is not used on the Internet

The address used in the local area network. The range (10.0.0.1 Murray 10.255.255.254) ② 127.X.X.X is reserved for use as a loop test.

Class B address

(1) Class B IP address. Consists of a 2-byte network address and a 2-byte host address.

The highest bit of the address must be "10".

For example: 10XXXXXX.XXXXXXXX.XXXXXXXX.XXXXXXXX (X stands for 0 or 1)

(2) Class B IP address range: 128.0.0.1 Murray 191.255.255.254

(3) the private address and reserved address of Class B IP address ① 172.16.0.0Murray 172.31.255.254 is the private address ② 169.254.X.X is the reserved address. If your IP address is automatically obtained from the IP address, and you have not found an available DHCP server on the network. You'll get one of the IP.

191.255.255.255 is a broadcast address and cannot be assigned.

Class C address

(1) Class C IP address. Consists of a 3-byte network address and a 1-byte host address.

The highest bit of the address must be "110".

For example: 110XXXXX.XXXXXXXX.XXXXXXXX.XXXXXXXX (X stands for 0 or 1)

(2) Class C IP address range: 192.0.0.1 Murray 223.255.255.254. (3) A private address in a Class C address: 192.168.X.X is a private address. (192.168.0.1 Murray 192.168.255.255)

Class D address

(1) Class D address does not distinguish between network address and host address, and the first four bits of its first byte are fixed as

1110 .

For example: 1110XXXX.XXXXXXXX.XXXXXXXX.XXXXXXXX (X stands for 0 or 1)

(2) Class D address range: 224.0.0.1 Murray 239.255.255.254

Class E address

(1) Class E address does not distinguish between network address and host address, and the first four bits of its first byte are fixed as

1111 .

For example: 1111XXXX.XXXXXXXX.XXXXXXXX.XXXXXXXX (X stands for 0 or 1)

(2) Class E address range: 240.0.0.1 Murray 255.255.255.254

Subnet mask

Brief introduction

Class A, Class B and Class C IP addresses are often used in the Internet. Through the hierarchical division of network number and host number, they can adapt to different network sizes. With the development of computer and network technology, there are more and more small networks, and it is a waste for them to use class C network numbers. Therefore, in practical application, the IP address is re-divided so that the third byte represents the network number and the rest of the host number. The network number part and the host number part of the re-divided IP address are distinguished by a subnet mask (also known as a subnet mask). The subnet mask is also represented by 4 bytes and is a 32-bit binary value that corresponds to the 32-bit binary value of the IP address. The 32-bit binary value for the IP address. The network number in the IP address is represented by "1" in the subnet mask, and the host number in the IP address is represented by "0" in the subnet mask. The function of the subnet mask is to distinguish whether the hosts on the network are in the same network segment, that is, the subnet mask is used to distinguish the network number and host number of the IP address.

By default, if there is no subnetting: the subnet mask for a Class A network is 255.0.0.0

The subnet mask for Class B networks is 255.255.0.0, and the subnet mask for Class C networks is 255.255.255.0.

With the subnet mask, the IP address is identified as follows: for example: 192.168.1.1 255.255.255.0 or identified as 192.168.1.1 hand 24 (24 represents the number of "1s" in the mask)

How to calculate the number of computers that the subnet can hold? What do you think of the network logo?

Related calculation

Example 1 calculate the capacity of the subnet mask

How many computers can the 255.255.232.0 subnet mask hold?

Method

Step 1: convert the subnet mask to binary 11111111.11111.11101000.00000000

Step 2: count the number of zeros behind you, and there are 11 in total, which is 2 ^ 11 to the power, which is equal to 2048. (note: in the host number, all zeros are reserved addresses and all ones are broadcast addresses, so they are not available primary number addresses. The network number is the same. The subnet number can be all-zero and all-one), so this subnet mask can hold up to 2048-22046 computers.

Example 2 calculate the subnet mask

There are 50 computers in a classroom to form a peer-to-peer local area net. what is the most appropriate subnet mask?

Train of thought

First of all, in terms of quantity, we can judge which type of IP in ABC. From 50 computers, we can see that class C IP is the most appropriate, but the default subnet mask of class C is 255.255.255.0, which can hold 254computers, which is obviously not appropriate. How much is the appropriate subnet mask?

Method

2n (the number of zeros after the subnet mask is converted to binary) > = 50 from this formula we can draw the following conclusion: Number6

So we can get the binary form of the subnet mask: 11111111.11111.111111.11000000, and then convert it to decimal form: 255.255.255.192, so the most appropriate subnet mask is: 255.255.255.192.

Example 3 calculate the number of subnets

Step 1: determine which of the three categories the IP belongs to. It can be known that their network numbers are the first 8 bits of Class A, the first 16 bits of Class B and the first 24 digits of Class C. The second step: turn the subnet mask into binary to see how many 1s there are, and subtract the number of 1s from the first step, which is the number of bits in the subnet. Step 3: if the number of subnet bits is n, it can theoretically be divided into 2n subnets.

Example 4 calculate the network segment identity and host identity

The question is how to determine that two IP addresses are on the same network segment? Analysis.

If you want to be in the same network segment, you must achieve the same network identity, then how to calculate the network identity? The network identity of all kinds of IP is different.

For category A, only the first paragraph is taken. Type B, only the first and second paragraphs are taken. Class C, only the first, second and third paragraphs are taken.

Method

Just AND (and) each of the IP and subnet mask. AND method: 0 and 1: 00 and 0: 0 1 and 1: 1

Examples to determine whether IP:12.196.132.54 and 56.196.56.165 are in the same network segment. (default subnet mask) step 1: convert these to binary IP1:12.196.132.54 00001100.10000100.00110110 IP2:56.196.56.165 00111000.11000100.00111000.10100101 subnet mask: 255.0.0.0 111111.00000000.0000000000000000000 second step: AND the IP with the subnet mask IP1 AND subnet mask = 000010.00000000.00000000.00000000 subnet mask = 001100000000.00000000.00000000 The result is converted to the decimal IP1 network ID: 12.0.0.0 IP2 network ID: 56.0.0.0 so it can be known that they are not the same network segment. Calculate the host identity step 1: invert the subnet mask: 00000000.11111111.1111111111 step 2: AND it with IP IP1 AND subnet mask = 00000000.11000100.10000100.00110110 IP2 AND subnet mask = 00000000.11000100.00111000.10100101 third: convert the result to the decimal IP1 host ID: 0.196.132.54 IP2 host ID: 0.196.56.165

Subnetting

Example: IP:192.160.12.50 (this can be the network number) subnet mask: 255.255.255.192 first step: convert the IP address and subnet mask to binary IP address: 11000000.100000.00001100.00110010 subnet mask: 11111111.1111111111.11000000

Step 2: AND the IP address and subnet mask

Because the mask is 255.255.255.192, the interval between them is 256-192 broadcast 64 broadcast address: next subnet-1 So the broadcast addresses of the two subnets are 192.160.2.127 and 192.160.2.191 respectively. The first subnet number: 11000000.100000.00001100.00000000 (192.160.12.0) the second subnet number: 11000000.100000.000010.01000000 (192.160.12.64) the first broadcast address: 11000000.100000.00001100.10111110 (192.160.2.127) the third subnet number: 11000000.10000001100.10000000 (192.160.12.64) . 12.128) second broadcast address: 11000000.10100000.00001100.10111111 (192.160.2.191) fourth subnet number: 11000000.100000.00001100.11000000 (192.160.12.192) this network segment can be divided into four subnets But there are only two available subnets (22-2): 192.160.12.64 and 192.160.12.128

fifteen

STUB region

Type 4 and type 5 LSA are not allowed in the st ub area

To put it bluntly, you cannot introduce external routes.

16DD message

The D-D message has two functions: one is to negotiate the master-slave relationship, and the other is to negotiate the master-slave relationship.

Is a summary of the expression of LSA

seventeen

IGP IGP is an interior gateway protocol, and IS-IS;IS-IS is a link-state protocol using a link-state algorithm.

eighteen

EGPEGP is an external gateway protocol, and BGP;OSPF is a link-state protocol that uses a link-state algorithm.

nineteen

Vlsm

VLSM (Variable Length Subnet Mask variable length Subnet Mask), a network allocation mechanism that produces subnets of different sizes, means that a network can be configured with different masks. The idea of developing a variable-length subnet mask is to have more flexibility when dividing a network into multiple subnets while retaining a sufficient number of hosts per subnet.

twenty

× × ×

The full name of × × is a virtual private network, which is used for remote connection. × × access is to establish a virtual private tunnel in the public network to connect.

twenty-one

Routing table learning

Routing table learning first look at the mask long; second look at the priority (when different routing protocols); third look at the cost value (ospf protocol).

two

The message between the DHCP relay and the DHCP server uses A.

Unicast unicast broadcast broadcast multicast Multicast Anycast anycast

Neighbor Discovery Protocol in IPv6 is a very important protocol. It implements a series of functions, including address resolution, router discovery / prefix discovery, address automatic configuration, address duplicate detection and so on.

Routing table learning first look at the mask long; second look at the priority (when different routing protocols); third look at the cost value (ospf protocol).

two

VLAN partition method

a. Division based on port B. Partition based on MAC address

c. Division based on port attributes D. The partition based on the protocol E. Subnetwork-based partition

twenty-three

Vlan

What are the following advantages of VLAN? ABCDEF .

a. Reduce the cost of movement and change

b. Set up a virtual working group

c. Users are not restricted by physical devices, and VLAN users can be anywhere in the network

d. Limit broadcast packets and improve bandwidth utilization

e. Enhance the security of communications

f. Enhance the robustness of the network

twenty-four

MAC address of the switch

The MAC address table of the switch can be learned by itself or added manually.

25 PING

When using the ping command, you can set the length of the ICMP message sent with-s

In a MSR router, using ping plus-an is the address of the source message.

If you want to specify the number of messages to be sent, add-c after ping.

Terminal-- Terminal monitor-- Monitoring debugging-- debugging

Display history-area display history area

Display history-command display History Command display history-cache display History Cache

Dir displays directory or file information; pwd shows the path of the current file system; path means path but does not have this command; D does not have this command

26 suffix

On MSR routers, by default, the configuration file is suffixed with _ _ ordered _.

A. .bin B. .sys C. .txt D. .cfg

Parsing: on a MSR router, bin is the application file and cfg is the configuration file

27 TCP/UDP Common Fields

The common fields of TCP and UDP are checksum, serial number, source port and destination port.

28 maximum rate

The maximum speed of V.35 can reach 2Mbps, the maximum speed of multiple time slots bundled with PRI E1 can reach 1920Kbps (about 2Mbps), and the maximum speed of BRI can only be 128Kbps.

29 network switching mode

There are two switching modes in the network: one is packet switching, the other is circuit switching.

1 packet switching is a Store-and-Forward switching-based switching method.

2 the transmitted information is divided into packets of a certain length and forwarded in terms of packets.

3 each packet contains the address identities of the receiver and the sender, and the packet can be forwarded directly without any operation, thus increasing the delay

4 packet switching includes frame-based packet switching and cell-based packet switching.

thirty

V.24 V.35

The difference between V.24 and V.35 is that V.24 can work in the same asynchronous mode, while V.35 can only work in synchronous mode. BRI/PRI is used for ISDN (Integrated Services Digital Network), and there is a slight difference between them. BRI (basic rate interface) has a rate of up to 128Kbps PRI (main rate interface). It is divided into PRI E1 and PRI T1 PRI E1 (usually used in central Europe, China and other places) is 30 64Kbps B channel (transmission user data) and 1 64Kbps D channel (transmission control command). Its highest rate is 1920Kbps. PRI T1 is the B channel of 23 64Kbps and the D channel of 1 64Kbps, and its highest transmission rate is 1472Kbps. The default mode of link encapsulation is PPP. As for G.703, it is an enhanced version of E1, so you can use G.703 if you want to run voice on the link. G.703 is also divided into two types of cables: 75 ohms of unbalanced coaxial cable and 120 ohms of balanced twisted pair.

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