What is a network bridge and how does it work
You must have also heard of bridge in communication. Many will also know about it, but if it does not exist, we will learn about it today, what is this bridge after all?
When creating a road, which must be crossed by a river, engineers build bridges in such places. This bridge was constructed to connect two parts to the site. Since no car or bus can swim through the water, they need a bridge to get from one place to another.
On the other hand, if we talk about computer networks, the bridge also performs the same function. It is used to link two or more Local Area Networks (LANs) together. In this, cars, or data (talking about the network then), are using the bridge to go to different parts of the network.
These devices are also similar to routers, but they do not analyze the data they are forwarding. For this reason, bridges are very fast in terms of data transmission, but they are not as versatile as routers.
For example, a bridge cannot be used as a firewall like most routers. The bridge can transfer data between different protocols (such as Token Ring and Ethernet) and operates at the Data Link Layer or Level 2 of the OSI model.
That is why today I thought why you should get complete information about what a bridge is and how it works, so that you can get acquainted with a device that is very special to the topic of networking. Then let’s start without delay.
What is a network bridge
This bridge is such a repeater, which has such a function that it filters content, so it reads the MAC addresses of both the source and the destination.
They are used to connect two local networks that operate in the same protocol. It has one input and one output port, making it a two-port device. This device operates at the data link layer of the OSI model.
These bridges are very useful for filtering the data load of traffic, which divides it into segments or packets. They are used to reduce the traffic load on a LAN or other network.
These bridges are actually passive devices , as there is no interaction between bridges and bridge paths.
How do Network Bridges work?
Now let’s find out how these mesh bridges work. Bridge devices scan incoming network traffic and determine whether packets are to be forwarded or discarded, depending on their destination.
For example, an Ethernet bridge first checks every incoming Ethernet frame, including the source and destination MAC addresses – sometimes frame size – while processing individual forwarding decisions.
This network bridge operates at Layer 2, which is the data link layer of the OSI model. It connects many parts of the network in this layer. Bridge not only broadcasts traffic from one network segment to another, but also manages the traffic together.
Bridges are used to send bridge table frames over network segments. This bridge table is initially empty. It is mobilized through the bridge, where it begins to receive frames from nodes (computers) that are connected to network segments. A bridge table is also called a database redirect.
If the address entry is not found in this table, for this received frame, the frame will be broadcast to all ports of the bridge; Then the destination network node responds, and the path is generated.
In general, if the bridge receives the frame from the network node, it checks the table and finds the destination MAC address by itself. Whereas, based on this MAC address, the bridge determines whether it needs to filter, flood, or copy the frame into the corresponding network segment.
Let’s understand the whole process properly
1. If the destination node is on the same side of the network segment that the frame comes from, the bridge prevents that frame from going to other network segments. This is called filtering.
2. If the destination node is located in another network segment, the bridge forwards the received frame to the appropriate network segment.
3. Whereas if the destination address itself is unknown to the receiving frame, the bridge forwards it to all parts of the network except for the source address. This process is called flooding.
bridge types
If you talk about the type of bridge, then you can divide it into 4 parts. Now let’s know the types of bridges
transparent bridges
These are those bridges where the stations are completely unaware of the bridge’s existence, which means whether a bridge has been added to the network or deleted, so reconfiguring these stations won’t be necessary at all.
These bridges mainly use only two operations, i.e. bridge forwarding and bridge learning.
When the bridging process occurs, it creates a bridging table with itself where it stores the MAC addresses of many different terminals. Using this, next time this table helps bridgers to send the data packet to the specified location .
But when a particular address does not meet the contents of this bridging table, the data packet is forwarded to every terminal connected to the LAN, except for one computer from which it is sent. This type of bridge is called a transparent bridge.
source routing bridges
In these types of bridges, the routing process is carried out by the source station and the frame itself determines the path it has to follow.
In this, the host can discover the frame if it wants, so only a special frame called discovery frame should be sent. which are propagated throughout the network in all possible paths which are related to the destination.
When the source computer displays the path information between packets, this type of bridge is called a source path bridge. These bridges are mostly used in Token Ring networks.
Transparent Learning Bridge
This transparent bridge tracks the user’s location through the source and destination address. When the frame is received in the bridge, it checks the source address and destination address.
In this the destination address is stored if it is not found in the routing table. Then the frame is sent to all LANs in which only those LANs are excluded from where that frame comes from.
The source address is also stored in the routing table. If another frame is accessed where the previous source address is now its destination address, it will be forwarded to that port.
The physical structure of transparent bridges does not allow loops in the network. This is the limitation that occurs on the transparent learning bridge.
The entire operation of the bridge is operated by the bridge processor who is responsible for routing traffic through its ports. In this, the processor decides the destination ports of the associated MAC addresses and for this they access the routing database.
When a frame arrives, the processor checks the output port in the database to which the frame will be relayed. If the destination address is not in the database, the processor will broadcast this frame to all ports, except for one port from where this frame comes from.
This bridge handler also stores the source address in the frame because this source address can become the destination address of another incoming frame. This learning bridge is built entirely on trust.
Transparent bridge extending in the shape of a tree
The last type of bridge is the transparent span bridge. These bridges use the entire structure of a subnet so that they can create a loop-free operation.
In this, the received frame is checked in the same way as described below. The destination address of the accessed frame is checked with the help of the routing table present in the database. It requires more information, so the port of the bridge is also stored in the database.
This information is called port state information and it helps determine whether or not a port can be used for a destination address.
This port is either in a block state to complete spanning tree operations , or is in a redirection state. Whereas if the port is in the forwarding state, the frame will be forwarded through the port.
The port has a different state like; It may be in a state of ‘ disabled ‘ for reasons like maintenance or it may be temporarily unavailable, if the databases in the bridge have been changed because the routed network may have been changed which is why this is happening.
What are the advantages of network bridges?
Although there are many advantages of such bridges, let’s get to know them.
1. Bridges have very simple configuration modes.
2. Also, these bridges are very easy to use and very cheap if compared to other networking devices.
3. This is a very good option for keys and with their help it is possible to perform micro-segmentation.
4. With their help, the load on the data link layer can be reduced. It also appears to be completely semi-transparent on the Mac layer.
5. It can be effectively programmed not to allow packets from micro-networks.
6. Bridges are very reliable if someone wants to reduce their bandwidth usage.
What are the disadvantages of network bridges?
Let us now know about the defects of bridges.
1. They are unable to read certain IP addresses; They are more interested in MAC addresses.
2. We cannot use bridges to create a communications network that uses different architectures.
3. It transmits all kinds of broadcast messages, so bridges are completely unable to limit the range of these messages. Very large networks cannot rely on these bridges; Therefore, large networks like WAN that have a specific IP address cannot use it.
4. This is a bit expensive if we compare it with the repeaters and hub.
5. Bridging is more convenient to handle the load of LAN traffic data. They cannot handle a more complex and variable data load like it does in a WAN.
6. It works a little slower than repeaters because there is a filter inside.
Why should bridges be used?
Bridges are very important to some networks because over a period of time the networks split into different parts, which are geographically far from each other.
In such a case some of these devices are needed so that these networks can be interconnected, so that they can also become part of the whole network. For example, a split LAN, if there is no medium to connect the separate LAN parts together, the growth of the enterprise may not occur properly. This bridge is one such tool that can join these local networks.
The other thing is that LAN (eg Ethernet) may have a limit in transmission distance. We can overcome this problem, as we can use bridges as repeaters, so that we can easily connect a geographically wide network with the help of bridges within a building or a campus.
So we can say that geographically challenged networks can be easily created by Bridges.
The third reason is that the network administrator can easily control the amount of traffic that goes through the bridges and is sent over expensive network media.
There is a fourth reason, these bridges are a kind of plug and play device, which is not configured. If a device is removed from the network, the network administrator does not need to do this work to update the bridge configuration, because bridges are self-configured. Together they help transmit data.
What did you learn today
I hope you liked my article What is Network Bridge. I have always been trying to provide complete information about the type of bridge to my readers so that they don’t have to search any other sites or the internet in the context of that article.
This will also save their time and they will also have all the information in one place. If you have any doubts about this article or if you want there to be some improvement in it, you can write low comments on it.
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