The difference between ADSL bridging mode and router mode

Early domestic ADSL line access are bridge mode, by ADSL modem and computer, in the computer to allocate fixed IP address, boot can access to the local terminal equipment into the Internet. However, when the user does not boot on the Internet, IP is not to be exploited, will cause the current increasingly scarce public network IP resources waste, so there has been a PPPoE dial-up ADSL access.

PPPoE dial-up can enable the user on the power-on dial-up access to the local equipment, by the local equipment allocated to a dynamic public network IP, so the public network IP tense situation has been alleviated. At present the domestic ADSL Internet way, basically is the way of PPPoE dialing. PPPoE dial-up after the advent of ADSL access devices--ADSL modem (ADSL modem) has a new brother products, called ADSL ROUTER (ADSL router). This equipment has ADSL modem's most basic bridge function, so individual products are also called ADSL bridge/router (ADSL bridge Router), commonly known as "lead the way by the ADSL modem."

ADSL ROUTER has its own PPPoE dial-up software, and can provide DHCP services, RIP-1 Routing and other functions, so it is ported a small number of router functions. However, it is not that PPPoE dial-up is not bridged, the common network of such as: ADSL MODEM + PPPoE dial-up software (such as Enternet 300).

There are individual local telecom operators still advocate the general ADSL MODEM, so there is no routing function, in fact, is not to encourage users "first-line multiple machines."

However, the current ADSL access Equipment manufacturers competition is fierce, so ADSL modem has been basically discontinued, and the production of ADSL ROUTER, which is now called the majority of ADSL modem are "leading the way", that is, ADSL access equipment is basically ADSL ROUTER.

Because of the different networking schemes, ADSL router has a bridge mode and a mode of operation.

If you have a small number of client home users or Soho users, you can directly use the PPPoE routed--routing mode, by ADSL router for PPPoE dial-up and routing. You can also use RFC 1483 bridged, then access the PC, run PPPoE dial-up software on your PC to dial, or access a broadband router, which is dialed by the built-in PPPoE dial tool for the broadband router.

If in a multi-user environment, the number of clients, such as: Internet cafes, enterprises, communities, often ADSL ROUTER plus broadband router network form, when most of the ADSL ROUTER work in bridge mode, by the broadband router to dial function, and assume the route of the work, This is because ADSL router has a low routing capability and can degrade or cause a panic failure when handling a large number of client routing requests.

So, bridge mode and routing mode are in fact for ADSL router.

What is bridging mode

ADSL Router Bridging mode has a formal professional name called RFC1483 Bridge. The RFC1483 standard is developed for the encapsulation and transmission of MULTI-PROTOCOL packets on the network layer, and is now widely used in ATM technology to be the encapsulation standard of processing multi-protocol packets on ATM networks.

RFC1483 simulates the bridge function of Ethernet, it encapsulates the packet of network layer on the Data link layer llc/snap. After the RFC1483 ATM package of Ethernet frame is finished in ADSL modem, transparent transmission of data packets is completed through the permanent virtual circuit of PVC on the client and the end network.

ADSL RFC1483 Bridge access mode is ADSL broadband access the most basic form, but also become the basis of other access methods, the general ADSL router factory also default in the bridge mode.

ADSL Router Factory initial value is used for a single computer bridge mode, that is, its current operating mode is placed in "bridge enable (bridging enabling)". In the pure bridge mode, ADSL router is only a common network bridge, its function is simpler.

Typically, a proxy server or gateway device is required to bring together communications from the LAN and then connect to the external network. You need to run PPPoE dial-up software on a proxy server or gateway device. Bridging methods can be assigned by the Bureau of fixed IP, can also be matched with dial-up software can be set to automatically obtain, or assign fixed IP need to be set on the PC side.

What is routing mode

ADSL ROUTER routing mode generally refers to the ADSL ROUTER in the "ROUTER Enable (routing)" mode of operation, it has PPPoE dial-up, NAT, RIP-1, such as a small number of routing functions.

PPPoE full name is the point to point Protocol over Ethernet (LAN-based point-to-point communication protocol). It is based on two widely accepted standards: LAN Ethernet and PPP point-to-point dial-up protocol.

In the ADSL router, the RFC1483 bridge package is used to LLC/SNAP and encapsulate the PPP package issued by the terminal, and the dynamic access of PPP is realized by connecting the two ends of the PVC in the connection between the ADSL modem and the network side broadband access server.

For the service provider does not need to spend huge sums of space to transform, set up IP address binding users to support the way of the special line. This makes PPPoE more advantageous than other protocols in broadband access services. So it is becoming the best choice for broadband Internet.

In routing mode, ADSL router is an independent quasi system, its own PPPoE dial-up and do Nat, become a stand-alone gateway, do not need a machine dedicated to the boot and set up a shared Internet function for others to do the gateway, or do not need a broadband router to do the gateway, Connect directly to the LAN switch to share the Internet.

Advantages of opening a route:

(1) Do not need to use a computer to do the server, any computer boot can be online.

(2) The only IP address is obtained by ADSL router, the external attacks are all used for ADSL router, which can protect the computer sharing the Internet to some extent.

ADSL Router routing mode enables routing mode, which eliminates proxy servers and dial-up software or broadband routers. However, due to the limitations of hardware conditions, ADSL routing can only be used for shared applications with only a few computers, such as small networks such as homes and dormitories. And for enterprises at dozens of, and even hundreds of applications, ADSL routing is difficult to do.

In the enterprise environment, in the ADSL running in the routing mode, there may be some problems, such as: frequent ADSL link disconnected; The ADSL big cat dies, must reboot.

ADSL routers and broadband routers have significant performance differences in routing. This behavior occurs because of the hardware structure. ADSL router CPU chip may be low-end network processor, such as: ARM7, the main frequency of only mhz,sdram memory is very small. Now the mainstream broadband routers, CPU frequency is up to 100Mhz above, SDRAM memory 16M above. There is also a difference in the ability to deal with the SOFTWARE function, the session capacity is much less than the broadband router.

In other more advanced functions, broadband routers have added such as SPI Firewall, DOS protection, IP filtering and other security mechanisms, as well as DHCP, DMZ, virtual server, DDNS and so on functions, these ADSL modem does not have.

In a certain scale network application, using ADSL router route is reluctant, performance and function is limited, but should choose "more professional" broadband router. In addition to family, Soho and other micro-network environment, the correct idea should be--ADSL router honestly in the bridge mode to do access, broadband router routing and security mechanisms, and other special applications.

Summary: For the current domestic broadband access to the main force, ADSL technology has many kinds of line packaging, and from these packaging methods derived from two so-called working mode: bridging mode and routing mode. Face these two patterns, some netizens will be at a loss, I do not know what kind of work mode to choose.

In fact, for the domestic universal ADSL PPPoE virtual dial-up, both models can be used, but because of the size of the network and what kind of work mode should be used better.

Overall: If the family and Soho Micro-network, it is recommended to use the routing mode, if the Internet cafes, schools, enterprises, communities and other large network, the proposed bridge mode, plus broadband routers to perform PPPoE virtual dialing and routing functions.

Supplementary Note:

The difference between Bridge and routing mode of ★ADSL modem

ADSL modem is divided into bridge (by default) and routing mode, when using a computer dial-up Internet, if not deliberately configured ADSL route, the actual use is bridging function, in this case, the Internet access to IP directly to the PPPoE dial-up computer, Modem is only responsible for the forwarding of packets, not the attack itself, which is why a machine dial-up Internet access if not open the firewall will still be the reason for the external network attack.

And when the ADSL modem opened the routing function, the IP access and attacks are directly loaded on the modem, then the modem is like a proxy server or firewall, the internal network through the modem sharing of the machine are protected in the Internet, So many PCs through the modem open circuit by the Internet, basically the shock wave patch does not hit, can be protected from the shock wave virus attack.

★ Bridging and Routing image interpretation

The process of transferring data over a network can be likened in the following ways:

Comparing the packets transmitted on the network to a box of goods, we are ready to send the goods from point A to point B.

The first step: packaging the Goods (packets), prevent falling apart or stolen on the road (lost or monitored), in the packaging process in order to facilitate the easy use of B receiver to untie the packaging, the world of this packaging method has been stipulated (the agreement is born, our common TCP/IP is such a protocol), The 7-Layer wrapping paper (OSI 7-layer model) is added to a.

The second step: packaging, it is necessary to transport the goods, there are two ways, one is bridging, one is routing. The bridge is equivalent to a section of the road, the goods through the road to B transmission, and the route is equivalent to traffic police, he will tell the goods which is the most recent, the fastest route to point B, so at the key crossroads to place the necessary routers to command the cargo route.

The third step: when the goods arrive B, will be in accordance with the above agreed binding mode (TCP/IP protocol) to untie the packaging.

Bridge mode and routing mode are relative to the link layer. The bridge mode works on the link layer, which means that only the IP packets coming over the network layer are transmitted without any processing such as routing forwarding, packet filtering, and relative to a channel. Routing mode works on the network layer, the general routing device is the work of this layer above, this level of content is rich, the device can be PPPoE dial-up, there is a firewall, Nat function.

Bridging is equivalent to an ordinary switch connection, which connects devices of the same address segment or VLAN. Routing is the connection of different segments of the network. You can even do address translation.