Shulou(Shulou.com)06/02 Report--

one。 Why do we need trunk links

In the previous article, our computers connected to the same switch can communicate with each other, and our two switches and hosts have their own broadcast domain. How can we achieve VLAN communication between switches now? We need Trunk links.

II. The principle of trunk link

Vlan10 communicates with another vlan10 across the switch. We need to connect a cable.

But if we have a hundred VLAN, and our switch has only 8, 16, 24, 48 ports, then we need trunk links.

First of all, our trunk link is a public link. How does the data from VLAN10 get to VLAN10? at this time, we need identification to distinguish different VLAN.

The first is Cisco's proprietary standard.

The second is our commonly used 802.1q logo.

Let's get a general idea of what the frame format is.

DA: destination address, SA: source address, type, data

TAG: marks this frame with an 802.1q tagged message

Priority:3 bit user priority, which is not used by 802.1q

CFI: commonly used in Ethernet and token networks, this value is usually set to bit 0

VLAN ID

three。 Let's configure the Trunk link through GNS3

1. Let's practice the line and write down the IP address and VLAN.

two。 Let's configure the capacity first.

3. Turn off routing and create a VLAN10

4. Create VLAN20 and view VLAN

5. Enter port, access link, and fill in VLAN10

6. Enter the SW2, create a VLAN, and access the link

7. We enter the trunk link, port 1max, port 2, SW1 and SW2 are set.

8. Let's go to PC1 and PC4 and see if we can get through.

9. Let's use the package grab software to check it.

Generally speaking, there are two trunk links in the enterprise for backup.

11. Let's create another one.

twelve。 We set it up in SW1 and SW2 respectively.

13. When we set it up, we must turn it on.

14. When it's turned on, we're going to tie the two links together.

15. Let's try to see if we can still connect if we disconnect the F1amp 2 port.

First of all, we use the regular PING command

16. Go to SW1 and SW2 and turn off F1Company2. Turn off shut down.

17. Let's check whether the regular PING just now can still work.

four。 The principle of layer 3 switch

Layer 2 switch is not as functional as layer 3 switch.

Layer 3 switching switch is a switch with some router functions. The most important purpose of layer 3 switch is to speed up the data exchange within a large local area network, and its routing function is also for this purpose, which can be routed once and forwarded multiple times. The regular process such as packet forwarding is realized by hardware at high speed, while the functions such as routing information update, routing table maintenance, route calculation, route determination and so on are realized by software. The machine has the function of routing and the function of switch! []

Process-based switching

Our layer 3 switch transmits data according to this table.

five。 Let's experiment with this layer 3 switch.

1. Let's add two routers and three hosts first.

two。 Configure SW1 with VLAN, port, TRUNK

3. We mark the address and VLAN for the layer 3 translation.

4. We assign TRUNK to SW2 and IP address to port.

5. We assign addresses and network cards to each host.

6. Let's test whether the three hosts can communicate with each other.

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