What is a bridged network?

[negru]

On Wiki article (https://en.wikipedia.org/wiki/Bridging_(networking)), I have found the following: Bridging connects two separate networks as if they are only one network (hence the name "bridging").

Could you explain this in more details?

[Georg Pauwen]

Hello,

have a look at the configuration snippet below. You have two layer 3 interfaces, by configuring them to be bridged, you can connect hosts on both interfaces that share the same broadcast domain. Your hosts use the IP address of the BVI (BDI in newer IOS releases) as their default gateway:

bridge irb
!
interface FastEthernet0/0
no ip address
speed auto
duplex auto
bridge-group 1
bridge-group 1 spanning-disabled
!
interface FastEthernet0/1
no ip address
speed auto
duplex auto
bridge-group 1
bridge-group 1 spanning-disabled

!

interface BVI1
ip address 192.168.1.1 255.255.255.0
!
bridge 1 route ip
bridge 1 protocol ieee

[Julio E. Moisa]

Hi

Imagine you have 2 different domains but using the same network prefixes, for exampel 10.0.0.0/24, you can use a router to merge these networks and it will be seen like one so you will not have overlapping. The following link could be useful:

https://www.cisco.com/c/en/us/support/docs/lan-switching/integrated-routing-bridging-irb/200650-Understanding-Bridge-Virtual-Interface.html

:-)

[Richard Burts]

It seems to me that a key aspect of answering this question

Bridging connects two separate networks as if they are only one network

is to consider whether we are connecting networks using layer 3 technology or layer 2 technology, Let us think about an example where we have two networks that are physically distinct and separated. It would be easy to connect these networks using layer 3 routers. But in this case we are using default gateways and routing logic that allow them to communicate but still treats them as separate networks..

If we connect these networks using layer 2 technology then a host in one network needs to be able to send an arp request to a host in the other network and to receive a response. No need for gateways that keep the networks separate. That is what bridging is about - being able to communicate at layer 2.between networks.

HTH

Rick

[spatuz]

One question to understand better. Bridging is used when we have two differemt network with same gateway and we want to connect them like this:

[Joseph W. Doherty]

Traditionally, a bridge was a device to connect L2 segments, but with intelligence as to whether a frame needed to be passed from one L2 segment to the other.  I.e. a bridge would learn L2 MACs on each side of it, and only if a frame came to the bridge, where the MAC was NOT know to be on the same side as received, would the bridge relay the frame to the other side.

You might have some experience using multi-port bridges, commonly now known as L2 switches.