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

1. What are the major directions of the Cisco router configuration?

In our computer network configuration, or in small businesses, the main thing to do is networking. There are many problems involved in networking. The first is how to divide the local area network. The second is how to connect the local area network and the local area network. The third is the configuration of access rights between intranet and extranet.

two。 Basic concepts?

Gateway (management IP address): the exit of a network, when one local area network accesses another local area network, the gateway needs to be used to control it and let it go out to visit other local area networks. if it is to exchange visits within the local area network, it does not need a gateway.

Routers and layer 3 switches can be configured with the network layer, which means that local area networks and local area networks can be accessed.

Layer 2 switches have no network layer, only the data link layer and the physical layer.

The configuration of the gateway of a network first depends on what equipment it uses. If the switch (whether you use layer 3 or layer 2), you can talk about the corresponding VLAN configuration IP address, this IP address is the gateway of the corresponding LAN, and then the switch is delimiting the switch port connected to the computer into the VLAN. The gateway of the router is better configured, as long as the corresponding IP address is configured at its interface.

3. What is the subnet mask for?

The subnet mask defines the attribution of the IP address.

For example, 255.255.255.0 defines a class C IP address. 255.255.0.0 defines a class B IP address.

We convert the IP address of a pc and its corresponding subnet mask into binary to do and calculate, and then do the same with another PC.

If it is found that the corresponding network number is the same, it is the same network, the same network can be accessed directly, and different networks need to go through the network.

Not all subnet masks are as regular as 255.255.255.0.

For example, things like 255.255.255.192 or 10.23.2.0 Universe 24 (this subnet representation is called CIDR, representing the first 24 1s and the last 8 zeros).

4. Why subnetting?

Disadvantages of two-level IP addresses: the utilization of IP address space is sometimes very low, and assigning a network number to each physical network will make the routing table too large and make the network performance worse; two-level IP addresses are not flexible. Since 1985, a subnet number field has been added to the IP address, which makes the two-level IP address become the third-level IP address. This is called subnetting. Subnetting has become the official standard protocol of the Internet.

The basic idea of subnetting is as follows:

Subnetting is an internal matter of a unit. The unit still behaves as an unsubnetted network.

Third-level IP address: {network number, subnet number, host number}. For all IP datagrams sent to a host of the unit from other networks, according to the destination network number of the IP Datagram, first find the router connected to the network of the unit. After receiving the IP Datagram, the router finds the destination subnet according to the destination network number and subnet number, and finally delivers the IP Datagram directly to the destination host.

5. How are subnets divided?

Subnetting is actually the process of designing a subnet mask.

Examples are as follows: a company has 4 departments with 25 computers in each department. How do you divide it?

A: class C address network can hold 255 units, and Class B network can hold more than 60,000, so we choose Class C network address.

So the 5th power of 2 = 32 > 25, you only need to set the host network active subnet mask 3 bits.

So the final subnet mask address is 27 1focus 5 zeros, so 225.225.225.224.

With 192.168.10.0, it is divided into 6 subnets.

192.168.10.32 192.168.10.64 192.168.10.96 192.168.10.128 192.168.10.160 192.168.10.160 192.168.10.192

6.icmp and ping and traceroute and ifconfig and ipconfig and netstat

Icmp is a network layer protocol: an Internet control message protocol used to find routing and connection problems.

Ping is one of the common network debugging tools. It sends an icmp request message to a host, which causes the recipient to send back the message.

Traceroute: this command is based on icmp tools. Executing traceroute host shows the path that the packet takes to reach the target host.

The network transmits in frames.

The format of the frame is the destination address source address type IP Datagram FCS

Among them, IP Datagram is very complex, including icmp protocol.

Ifconfig is the abbreviation of interface config, which is the configuration of the network interface.

Mainly displays the network card information.

Ipconfig is the same as ifconfig.

The netstat command is used to display statistics related to IP, TCP, UDP and ICMP protocols. It is generally used to verify the network connectivity of each port of the machine.

Netstat is a program that accesses network and related information in the kernel. It can provide reports on TCP connection, TCP and UDP snooping, and process memory management.

If your computer sometimes receives datagrams that cause errors or failures, you should not be surprised that TCP/IP can allow these types of errors and automatically resend datagrams. But if the cumulative number of error cases accounts for a significant percentage of the IP datagrams received, or if its number is increasing rapidly, then you should use netstat to find out why these situations occur.

Common dos commands

Show the contents of the current folder dir

Create a folder: md

Delete empty folder: rd

Create a file and write the content echo content > filename

View file contents type (print) filename

Delete files: del

Clear screen: cls

Netstat-an

Tracert ip/ domain name

Layer 4 protocol:

Application layer: app+ data

Transport layer: tcp/udp+app++ data

Network layer: ip+tcp/udp+app+ data

Data link layer: head frame + ip+tcp/udp+app+ data + tail frame, sent to the network card

7. Firewall?

In particular, routers should include some kind of firewall to defend your network against requests from uninvited guests. A firewall is a configuration of software and hardware that is located in a router between the Internet and a small network to protect a small network from Internet traffic. You can also equip each machine with a firewall so that each machine can filter incoming and outgoing data at the packet level. Each machine is equipped with a firewall, called IP filtering.

The system can filter packets in these situations:

When receiving a packet

When sending a packet

Or when forwarding the packet to another host or gateway.

8. Three interfaces in the virtual machine

VMnet0: this is used by VMware for virtual bridging networks; VMnet8: this is used by VMware for virtual NAT networks; 8. When we often do virtual machine systems under Windows, we usually produce two virtual network cards at the time of installation, one is VMnet1: this is VMware for virtual Host-Only networks, and the other is VMnet8: this is VMware for virtual NAT networks. Vmnet1: equivalent to a switch, as long as you put the IP address of your virtual machine and Vmnet1 in the same network segment, you can communicate VMnet8: it is equivalent to a switch, as long as you put the IP address of your virtual machine and Vmnet1 in the same network segment, you can communicate without configuration, as long as you make sure that the ip address of your virtual machine and the local link are in the same network.

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