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In this topology if PC 1 sends a broadcast way will it go?Assume that switch 1 and switch 2 or

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with any VLANs except the default VLANs and draw that router 2 is configured with subnet 10 110 on

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gigabit 00 and subnet 10 120 on gigabit 01.

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In other words, the router has an IP address such as the following configured on gigabit 00 and an 

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IP address of the following configured on gigabit 01.

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Where will traffic go if PC 1 sends a broadcast? What do you think? Ostinato order is a great little

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application that allows us to generate network traffic.

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So before I configure the PC to forward traffic what I'll do is configure the router with an IP address

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on each interface. No configuration has been done on the switches,

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so where will traffic go?

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If PC 1 sends a broadcast so show IP interface brief on the router shows us that both interfaces are

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up,

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apart from that I've done no configuration. Here's the console for PC 1 so I'll startup Ostinato and

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on the Ethernet interface I'm going to generate traffic.

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Now I need to use Ethernet 1 rather than Ethernet 0 on these Ostinato devices. 

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So I'll re-cable the network

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the principle however is the same.

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All I'm doing is flipping the interface number on the Ostinato devices

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but where will traffic go?

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So I'll start a new stream generation

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and I'll configure the PC to generate IP version 4 traffic that UDP traffic.

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I'll configure the MAC address as all ones in other words it's a broadcast frame for the IP version 4

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destination I'll set it to a broadcast as well.

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So destination MAC address is all ones

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In other words a broadcast, so IP version 4 destination is a broadcast.

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So what I'll firstly do is start a capture between the switch and the router and I'll also do it on this side

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and then I'll capture traffic between the switch on the left and Ostinato PC 2 as well as 3

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and 4.

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What I'll do in this case is send a thousand frames at one frame per second.

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Click Apply and start sending frames on the Ethernet 1 interface the frames being sent have increased.

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We've had about 10 frames sent now.

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So on the link between the switch and the router.

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So this is between IOS V layer 2 switch gigabit 00 and the router on gigabit 00.

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We are seeing that broadcast traffic, what about on this link here?

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So this is traffic between the router and switch 2 notice we don't see any UDP traffic.

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The broadcast traffic is not being received on this link.

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What about this link?

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So this is the link between IOS V layer 1 gigabit port 02 to Ostinato device 2 filter for UDP traffic.

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You can see the broadcast traffic being sent on that port so IP address and layer 2 address. So broadcast

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traffic is being sent here.

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What about on this link?

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So this is the link between IOS switch 2 gigabit 01 and Ostinato 3.

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No broadcast traffic is received there.

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And what about switch 2 Gigabit 02 to Ostinato device 4 no UDP traffic is received there but

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we are receiving it between the switch and the router and we are receiving it between the switch and

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the second ostinato device.

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So in other words a broadcast sent by this device is going to be flooded out of all ports on Alade to

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switch except the port in which it arrived

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but a router will block broadcast frames.

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Modern routers by default do not forward broadcast frames.

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So in this topology, we have what is called two broadcast domains.

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The router is blocking broadcasts on this link so broadcasts are not forwarded.

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Now, what happens if we put the PC into separate VLAN. I hope you enjoyed this video if it's been of benefit

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to you please like it and please subscribe to my YouTube channel.

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I wish you all the very best.