Shulou(Shulou.com)06/03 Report--

Hello, ladies and gentlemen. What I want to share with you today is the knowledge about VLAN and layer 3 switch. I will analyze it mainly from three aspects:

(1) knowledge of VLAN principle

(2) Overview of Trunk theory

(3) understanding of layer 3 switching

1. Knowledge of VLAN principle 1. Overview: split broadcast domain

(1) physical segmentation: the network is physically divided into several small networks, and routes are used to connect different networks to achieve communication.

(2) logical segmentation: the network is logically divided into several small virtual networks, namely VLAN. An VLAN is a switching network.

2.VLAN advantage

(1) Control of broadcasting

(2) enhance network security

(3) simplify network management

3. Static VLAN

Static VLAN, also known as port-based VLAN, is the most common VLAN implementation (a function on the switch).

Static VLAN explicitly specifies which VLAN the switch port belongs to, which requires manual configuration by the administrator. When the user host is connected to the port of the switch, it is assigned to the corresponding VLAN.

As can be seen from the above picture, host An and host C are within the range of VLAN 5, within a communication range; host B and host D are in VLAN 10, within a communication range.

4. (1) configuration of static VLAN

VLAN 0pr 4095 and 1006-1024 are used in the system.

1 is the default existence number, and you do not need to create it when using it.

1002-1005Jing 1025-4094 for user use, can be created, used and deleted.

(2) VLAN basic configuration step A. Create VLAN

-a.VLAN database configuration mode (older mode), but this mode only supports VLAN normal range for (1Murray Muyamo1005)

-b. Global configuration mode, which can not only support the normal scope of VLAN, but also configure the VLAN scope of extended scope that cannot be configured in database configuration mode (we used this mode in our lab).

b. Add the switch port to the corresponding VLAN; C. Verify the VLAN. Second, Trunk theory overview 1.Trunk overview: the main realization of cross-switch to enable hosts with the same VLAN to communicate.

Function: uses only one link and distinguishes different VLAN data by identification.

two。 Two types of links in switched networks

(1) access link: belongs to a VLAN, the link between the host and the switch.

(2) Trunk link: can carry multiple VLAN, the link between switch and switch, usually we also call the link between switch and router as trunk link.

3. Encapsulation marking process:

A.VLAN 10 sends data frames to the left switch, and the receiving port of the left switch binds VLAN 10 to receive data frames randomly. ```

b. In order for the right switch to recognize that this is the data frame of VLAN 10, thus marking it as VLAN 10, it is then sent to the right switch through the trunk link.

c. After receiving it, the right switch determines that this is VLAN 10, and then queries the host of VLAN 10. Finally, the right switch deletes the identity and forwards it to the host of VLAN 10.

Identification of 4.VLAN

There are two types of encapsulation for relay over Ethernet:

(1) ISL (Cisco Private Standard)

The ISL package has a total of 30 bytes: 26 bytes in the header and 4 bytes in the tail.

(2) IEEE 802.1q

The logo is 4 bytes, which is the length of TPID and TCI in the following figure.

Configuration steps for 5.Trunk:

(1) enter interface mode

(2) Select the encapsulation type

(3) configure the interface as Trunk. In addition, if you do not need the Trunk to transmit the data of a certain VLAN, you can delete the VLAN; from the Trunk, or you can add a VLAN to the Trunk.

(4) use the "show" command to verify the interface mode

Third, the understanding of layer 3 switching. Three-layer switching technology

(1) using layer 3 switching technology to realize the communication between VLAN

(2) layer 3 switching = layer 2 switching + layer 3 forwarding

two。 Traditional MLS2-2

(1) Exchange ASIC to learn layer 2 rewriting information from the layer 3 engine to create a MLS entry in the hardware

(2) responsible for rewriting and forwarding subsequent packets in the data flow

How it works: when VLAN 1 wants to communicate with VLAN 2, there will be a lot of packet transmission. When the first packet is transmitted to the layer 3 switch to query the layer 3 route, it is known that the network segment to VLAN 2 is forwarded. To forward the packet, it is necessary to re-encapsulate the packet. At this time, it is necessary to send an ARP query signal to VLAN 2 to obtain its MAC address. After reencapsulation, the route and the address of VLAN 2 are stored in the cache table, and then the packet is transmitted to VLAN 2. The subsequent packets only need to look up the cache table in the layer 3 switch and then transmit them to VLAN 2.

3. MLS based on CEF

CEF is a model based on topology forwarding

(1) forwarding Information Base (FIB)

(2) adjacency table

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