Resolve IP configuration parameters of network routers using bridging

A router is a basic device in man, Wan, and Internet. It connects to a remote computer network distributed in a certain region and forwards data packets based on the layer-3 IP address of the OSI reference model. The simplicity, openness, and scalability of IP technology make it widely used in the Internet and broadband network construction fields, which correspondingly promotes the development of IP technology. But in fact, because the man and Wan are also developed on the basis of the LAN, the existing router manufacturers still retain the bridging technology of the original LAN connection, in addition, the bridge technology can be flexibly deployed according to specific circumstances within a certain range to meet the specific needs of upper-layer applications. Therefore, the bridge technology still has significance. The following is an example of how to solve the problem by using transparent bridging after an IP address is configured on a Cisco 2610 router.

An error occurred while configuring the IP address directly.

The power dispatching department of the author relies on the energy management system EMS to control the operation of the power grid. in the case of an accident, the dispatcher needs to provide a backup EMS workstation in the distance, prevent scheduling paralysis and grid resolution from fire and other accidents, and ensure safe, economical, and high-quality operation of the grid. The remote backup workstation is located three kilometers away from the central scheduling and has a long distance. The scheme decides to connect the two ends with a Cisco2610 router, and use a 2 M bandwidth line in the middle. This is a small network structure.

The router's planned configuration is: Model Selection Cisco 2610; a 10 M Ethernet module NM-1E; a WAN module WIC-1T supporting 2 M bandwidth. Due to the general habit, the routing protocol uses IP addresses, but this leads us to a detour.

The lan ip address of the router A we configured is the same as the internal class C network IP address: 192.1.1.254, Mask 255.255.255.0, connected to the Cisco 5500 switch of the scheduling automation EMS main system; the IP address of the WAN interface module is A type of subnet address: 10.0.1.1 and Mask 255.255.255.252. Similarly, the lan ip address of vrob B is 192.1.2.254 and the Mask 255.255.255.0. the IP address of the WAN interface module is 10.0.1.2 and the Mask 255.255.255.252. After configuration, run the Show ip route command on the vro。 to view the route table. You can use the Ping command to Ping the ports between vrouters.

At this point, we thought it was a success. We added a static route to the server and remote workstation, but there was a problem when the system was started on the remote workstation. The program keeps prompting network connection errors and cannot download data tables from the server to the local shared memory. The system fails to start.

Transparent Bridging for broadcast

Does the program not support the TCP/IP protocol? We are puzzled. After finding the technical information of the system in detail and providing technical consultation to the manufacturer, I realized that although the program supports the TCP/IP protocol, some internal processes transmit data packets through broadcast, cannot be routed. How can I transmit broadcast data packets through a vro? Transparent bridging comes in handy.

"Bridging" refers to the process of forwarding network packets based on the link layer address of the OSI network model. After the bridging option is configured, the router processes all data frames on all interfaces and investigates the locations of each host in real time. If a frame is generated on an interface, an entry is embedded in a bridge to list the host sending data and the MAC address of the interface receiving data frames, in this way, the route table is constantly improved in communication. Transparent bridging makes the router transparent to the host, and its role is equivalent to a LAN switch. If two hosts communicate in the same LAN, data frames are not sent to other interfaces, because in the bridging table, data frames come from the same interface. If a frame is received, however, if the MAC address is not in its own bridging table, the frame will spread to all interfaces, and the bridging will spread all broadcast packets, occupying the effective bandwidth of the network, network congestion. We know that Cisco IOS supports multiple types of bridging, such as transparent bridging, encapsulation bridging, source route bridging, source route transparent bridging, and source route conversion bridging.

For Cisco Routers running transparent bridging, the "Spanning Tree Protocol" Spanning Tree Protocol can be used to avoid broadcast storms caused by bridging. The Spanning Tree Protocol uses the Bridge Protocol Data Unit Bridge Protocol Data Units to define the communication forms of each Bridge on the network. Its logical structure is like a tree, each Bridge is a branch of the tree and has its own path value, Bridge Id, and priority. The bridge with the lowest priority is used as the root. If the priority is the same, select the bridge with the lowest bridging ID. Data packets are transmitted through the path formed by the root bridge and other bridges. The bridge at the highest level blocks the interface and only receives BPDU data packets. This effectively solves the problem of broadcast spread. After understanding the Spanning Tree principle, we can have a specific purpose. The command to reconfigure the router is as follows:

DispatchA # config terminal! Select the ieee stp Spanning Tree Protocol. DispatchA (config) # bridge 1 protocol ieee! Select the router at the master scheduling end 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 router of the standby scheduling end, except for no priority, the other configurations are the same as above.

After the above work, the remote workstation and the host on the local network can be connected without any obstacles, and the configuration of the router is relatively simplified. The release delay of the database interface program on the server is appropriately extended. Now, the Program on the remote workstation starts normally. Although the real-time information is refreshed slowly, it can still meet the application requirements. The above example shows that although the bridge technology has its limitations, it is still an effective method and means to solve some specific practical problems. Although network technology continues to develop, while tracking new technologies, we should not ignore the fact that old technologies will still offer us great help in some places.

1. Tutorial on bridging and overwriting a Wireless Router
2. Router configuration newbie ---- bridging and Routing
3. Transparent Bridge Mode: how to achieve a shortcut between a valid IP address and a virtual IP address?