Using bridging to solve IP configuration parameters of network routers

Routers are the basic equipment of metropolitan area network, WAN and Internet, it connects the remote network of computer in a certain area, and forwards the packet according to the IP address of the third layer of the OSI Reference Model. The simple, open and easily extensible features of IP technology have made it widely used in the field of Internet and broadband network construction, which has promoted the development of IP technology correspondingly. But in fact, because of the metropolitan area network, WAN is also on the basis of the local area network developed, the existing router manufacturers still retain the original connection LAN bridge technology, and bridging technology within a certain range can be tailored to the specific circumstances of the flexibility to deploy, to meet the needs of users of the application of the specific requirements, So bridging technology still has the meaning of existence. The following is an example of a transparent bridging solution to the problem after you have difficulty configuring IP on the Cisco 2610 router.

Direct Configuration IP Failure

The Power Dispatch department of the author relies on the Energy management system EMS to control the operation of the power grid. In the event of an accident, the dispatcher needs to provide a standby EMS workstation in the distance to prevent the dispatch paralysis caused by fire and other accidents, and to ensure the safety, economy and high quality operation of the power grid. The remote standby workstation is located three km away from the center and is longer. The scheme decides to connect at both ends with the Cisco2610 router, and the 2M bandwidth line is used in the middle. The structure of this small network is as shown.

The router's schedule is configured to: Model selection Cisco 2610; a 10M Ethernet module nm-1e; a WAN module wic-1t that supports 2M bandwidth. For the general custom, the routing protocol uses IP, but this makes us take a detour.

We configure router A's LAN IP address consistent with the internal C-Class network address: 192.1.1.254,mask 255.255.255.0, connected to the Dispatch Automation EMS main system Cisco 5500 switch The IP network address of the WAN interface module is a Class A subnet address: 10.0.1.1,mask 255.255.255.252. Similarly, the LAN IP address of router B is 192.1.2.254,mask 255.255.255.0, directly connected to automation workstation, and the IP network address of WAN interface module is 10.0.1.2,mask 255.255.255.252. After configuration, use the show ip route command on the router to view the routing table and ping the ports between routers by using the ping command.

At this point we thought we were done and added a static route to the server and remote workstation, but there was a problem booting the system on the remote workstation. The program keeps prompting for network connection error, cannot download data table from server to local shared memory, system startup failed.

Transparent bridge Implementation Broadcast

Does the program not support the TCP/IP protocol? We were puzzled. In a detailed search of the system's technical information and to the manufacturers of technical advice, only know that the program although the TCP/IP protocol, but some internal processes are broadcast to send packets, can not be routed. How do I send broadcast packets over a router? The transparent bridge is now in handy.

"Bridging" refers to the process of forwarding network packets based on the address of the link layer of the OSI network model. When the router is configured with bridging options, all the data frames on all interfaces are processed and the location of each host is investigated in real time. If a frame is generated on an interface, a single entry is built into a bridge, listing the host sending the data and the MAC address of the interface that receives the data frame, so that the routing table is continuously perfected in the communication. Transparent bridging makes the router transparent to the host and acts as a LAN switch. If two hosts in the same LAN communicate, the data frames will not be sent to other interfaces. Because in the bridge table, the data frame is from the same interface, if you receive a frame, and the MAC address is not in its own bridge table, it will spread the frame to all the interface, bridge will also spread all the broadcast packets, Occupy the network's effective bandwidth, resulting in network congestion. We know that Cisco iOS supports multiple types of bridging, such as transparent bridging, package bridging, source routing bridging, source routing transparent bridging, and source routing transformation bridging.

The Cisco router, which runs a transparent bridge, uses the spanning tree Protocol to avoid broadcast storms caused by bridging spanning. The Spanning tree protocol defines the communication forms of bridges on the network through the Bridging Protocol Data Unit (bridge Protocol), whose logical structure is like a tree, each bridge being a branch of the tree, with its own path values, bridges IDs, and priorities. The lowest priority bridge is the root, and if the priority is the same, select the bridge with the lowest bridge ID. The packet is routed through the root bridge and other bridging paths, and the top bridge will block the interface and receive only BPDU packets, thus effectively solving the problem of broadcast proliferation. Understand the reason for the spanning tree, we can be targeted, reconfigure the router's command as follows:

Dispatcha#config Terminal

！ Select the IEEE STP spanning Tree Protocol.

Dispatcha (config) #bridge 1 protocol IEEE

！ Select the router on the primary dispatch side as the root bridge.

Dispatcha (config) #bridge 1 priority 0

Dispatcha (config) #interface ethernet0/0

Dispatcha (config-if) #bridge-group 1

Dispatcha (config-if) #interface serial0/0

Dispatcha (config-if) #bridge-group 1

Dispatcha (config-if) #

In the standby dispatch side of the router, in addition to not set priority, the rest of the configuration ibid.

After the above work, the remote workstation and the host on the local network can connect without hindrance, and the router configuration is relatively simplified. Then the server-side Database Interface program release delay appropriate lengthened, now the remote workstation program to start all normal, real-time information refresh although relatively slow, but still can meet the application requirements. The above example shows that bridging technology, although it has its limitations, is still an effective method and means to solve some concrete practical problems. Although network technology is constantly developing, while we are tracking new technology, we should not neglect that the old technology will still give us the overjoyed help in some places.