Studies are still clouds follow VLAN (6): VLAN routing between-VLAN-IT industry
VLAN routing between the need to
According to the knowledge acquired so far, we already know that even if the two computers connected to the same Switch So long as different VLAN can not belong directly Communicate . Next we will learn how different inter-VLAN routing, so that belong to different VLAN hosts can communicate with each other.
First of all, the first to review why not through the routing between different VLAN can not communicate. Communication within the LAN must be specified in the data frame header and the MAC address communications goals. In order to obtain the MAC address, TCP / IP protocol used is ARP. MAC address ARP resolution method is through the radio. That is, if the broadcast packet can not reach, then no way to resolve MAC addresses, which can not communicate directly.
Computers belong to different VLAN, meaning that belong to different broadcast domains, naturally not receive broadcast messages to each other. Thus, between computers belonging to different VLAN can not directly communicate with each other. In order to be able to inter-VLAN communication, need to use the OSI reference model, a higher level?? Network Layer information (IP address) to be routed. On the routing of specific content, have the opportunity to explain it in detail.
Routing function, mainly by general Router Provide. But in today's local area network, we often use the switch with routing capabilities?? Three switches (Layer3 Switch) to achieve. Next, let's look at each use Router And three inter-VLAN routing switch situation at the time.
Use the router to route between VLAN
Using the router between VLAN routing, and the Construction of VLAN across multiple switches similar situation at the time, we encounter "the how to connect the router and switch," this issue. Routers and switches, wiring, to the following two:
L to routers and switches are connected to each VLAN
L regardless of the number of VLAN, router and switch only with a network cable connection
Most easily thought of, of course, "the routers and switches to each VLAN as a unit with a network cable connection," the. The switch and router for Internet access link for each port set, then each router with network cable and port connectivity independent. As shown below, there are two switches on the VLAN, then it needs to set aside two-port switch and router for the Internet; routers also need to have two ports; between the two lines with two network connections, respectively.
If we adopt this approach, we should not be hard to imagine its scalability is a problem. Each adding a new VLAN, the port needs to consume routers and switches on the access link, but also the need to re-layout of a network cable. The routers, usually not with too much LAN interface. New VLAN, the VLAN to the corresponding increase in the required port, you must upgrade to the router LAN interfaces with multiple high-end products, this part of the costs and the overhead caused by re-wiring, all making such a connection Act as an unwelcome approach.
Then, the second approach, "regardless of the number of VLAN, only with a network cable to connect the router and switch" mean? When using a network cable to connect the router and switch, for inter-VLAN routing, you need to use link aggregation.
Realization process: First, connect the router will be used to set the switch port link aggregation, port on the router must also support the aggregation link. Agreement for both sides naturally link together must be the same. Then the definition of the router corresponding to each VLAN a "sub-interfaces (SubInterface)". Although the actual physical port with the switch connected to only one, but in theory we can split it into multiple virtual ports.
VLAN to switch from the logically divided into multiple units, which inter-VLAN routing for the router, it must have a corresponding virtual interface to each VLAN.
Using this method, even after the switch on the new VLAN, still only need a cable to connect switches and routers. Users only need a new router corresponding to the new VLAN sub-interfaces on it. Compared with previous methods, scalability to do, and they do not have to worry about needing to upgrade less than the router LAN interface, or re-wiring.
Because of the need to designate a port, so when the number of computers in the network over a certain number (eg hundreds), the setting operation becomes extremely troublesome. And the client with each change of the port, the port must also change their VLAN settings?? This is obviously not suitable for expanding that require frequent changes in the structure of the network up.
Dynamic VLAN The other hand, dynamic VLAN is in accordance with each port by the computer, at any time to change the port belongs to VLAN. This avoids changes to settings like the above operation. Dynamic VLAN can be roughly divided into three categories:
L MAC address-based VLAN (MAC Based VLAN)
L subnet-based VLAN (Subnet Based VLAN)
L User-based VLAN (User Based VLAN)
Those discrepancies mainly according to which layer of OSI reference model information to determine the port belongs to VLAN.
MAC address based VLAN, the port is through the query and records the card with the MAC address of the computer to determine the port-owned. Assumed to have a MAC address "A" is the switch set to belong to VLAN "10", then regardless of MAC address "A" of this computer connected to the switch which port, the port will be divided into VLAN10 and going. Computer connected to the port 1, port 1 is VLAN10; while the computer connected to the port 2, while port 2 is VLAN10.
Because the decision is based on their MAC address VLAN, and therefore can be understood as this is a second layer in the OSI set to visit the link approach.
However, based on MAC address, VLAN, the setting must investigate all computers connected to the MAC address and to log on. And if the computer network card exchanged, or need to change the settings.
Subnet-based VLAN, is connected through the computer's IP address to determine VLAN the port belongs to. Unlike the MAC address-based VLAN, even if the computer because the exchange of cards or other reasons to change the MAC address, as long as it's IP to
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