I'm doing something different with this... I'm releasing 3 versions of this content: An Article, a Short Video, and a Long video. Pick your favorite =). Article www.practicalnetworking.net/stand-alone/local-broadcast-vs-directed-broadcast/ Short Video th-cam.com/video/ZNXDbzaAM-I/w-d-xo.html Long Video th-cam.com/video/ny6MsSLb8_o/w-d-xo.html
Wish I could give you more likes. These are the kind of practical contents that I have been looking for, for so long. Thanks. Keep posting more videos like these. :)
Damn I tried explaining this exact information to someone over chat yesterday but this video illustrates it so much better! Thanks a million I have linked them to this fantastic explanation.
If I connected a computer to Hub1 and addressed it with 10.1.2.2/24, would it receive a Local Broadcast (255.255.255.255) from 10.1.1.1? The two machines would be on the same L2 network and on different L3 networks.
I wanted to ask for some clarification to see if I understand how broadcasts works with ping. It's my understanding that layer 2 broadcasts do not get delivered to the same port where the message originated from. That would mean that when Host1 sent a local broadcast through ping, it would not have received that ping request from itself on the wire (which your demonstration shows). Yet, the ping program shows a response from Host1. So, is it correct to assume that when the ping program recognizes a local broadcast request, it assumes that the user also wants a response from the originating host as well (since it is a part of the local network), so in addition to sending a local broadcast ping request it also sends a self-request (and response) internally? I was just confused because I did not see a broadcast messages delivered to Host1 or a ping response messages from/to Host1 on the wire, which makes sense network-wise but I wanted to know if receiving a response from the originating host was a feature of the ping program itself and not a part of how broadcasts work. Thank you for your video! I hope this question isn't too confusing haha
If I want to ping all the L2 Switches of a single site (whose management IP addresses are in same as Core switch )from core switch of that site , how to execute it ?
If all the management IP's are in the same Subnet, it would be as simple as pinging the directed broadcast IP address of that Subnet. Keep in mind, not all switches respond to broadcast pings by default.
Hi this is Noor one of your viewers thank you for shooting of such a nice videos, could pleas share how to install GNS3 and let me know about it, I mean could you please make a video on GNS3 installation and setup, how to configure it to function proper.
Hi Noor, glad you enjoyed the video =). I don't presently have plans for GNS 3 installation videos, but David Bombal has some good resources on the topic: th-cam.com/users/DavidBombalsearch?query=gns3
What if there had been 5 or more hosts in your ping example? The local broadcast ping only shows 4. If you add a switch (parameter) to ping continuously, would it then do all hosts on the network?
I've tried to replicate the same exact lab using eigrp but im not getting the same ICMP requests for broadcasts any idea why? Also what routing protocol did you use in this lab?
Sorry, one other question. So when you sent a local broadcast ping to 255.255.255.255, your demo showed that it was also a Layer 2 broadcast as well. Is that specifically a feature of the ping program? Or are all local IP broadcasts generally sent as layer 2 broadcasts as well? I would have expected a local IP broadcast to be delivered to the MAC address of the router, then the router would translate the message from a unicast frame to a broadcast frame and send it out to the whole network. Although that would mean the router would be delivering the broadcast frame to the same port which it was received. Why is this not the case? I would assume an IP local broadcast would need a router to function properly, yet your demonstration shows that a local IP broadcast frame would be translated to a layer 2 broadcast and not need the router in the first place.
Thanks for the video, it's great! I'd like to ask you if I have to enable the direct-broadcast option only on the interface connected to the network I want to do the direct broadcast (for example the interface of the ip 10.3.3.3) or to every interface on every router on which the ping will make its way?
Excellent question. You only need the `ip directed-broadcast` command on the router interface that would be expected to deliver directed broadcasts. So, in the example of the video it would be on R3's interface with the IP 10.3.3.3 -- the one facing Host 5/6/7. Glad you enjoyed the video and the article!
In the case of a company's topology that contains branch offices with various subnets and VLANs, can Direct Broadcast be used to troubleshoot connectivity and reachability issues at Layer 2 and Layer 3 levels? If this is one use case, are there other use cases of using Directed Broadcast when troubleshooting issues in modern network topologies? I would think Firewalls, DMZs, Proxy Servers, VPNs, WLANs and WANs are security considerations which will block or drop a Directed Broadcast packet whenever a Directed Broadcast is used as a troubleshooting tool.
You're on the right track... but keep in mind: (a) Most routers block directed broadcast to limit abuse (b) Most hosts don't respond to broadcasts by default So while in theory, you're right about the benefit for troubleshooting. In practice, the two points above would limit the effectiveness of troubleshooting with broadcast packets.
I'm doing something different with this... I'm releasing 3 versions of this content: An Article, a Short Video, and a Long video. Pick your favorite =).
Article www.practicalnetworking.net/stand-alone/local-broadcast-vs-directed-broadcast/
Short Video th-cam.com/video/ZNXDbzaAM-I/w-d-xo.html
Long Video th-cam.com/video/ny6MsSLb8_o/w-d-xo.html
Wish I could give you more likes. These are the kind of practical contents that I have been looking for, for so long. Thanks. Keep posting more videos like these. :)
Thank you for the kind words, Vidhya. Glad you enjoyed this content!
This topic has been driving me nuts for so long. This makes so much sense. Thankyou!!!
Glad it helped =)
Your channel is digital gold, and I really mean it ...
Thank you for the kind words, Cokegen =). Much appreciated.
Damn I tried explaining this exact information to someone over chat yesterday but this video illustrates it so much better! Thanks a million I have linked them to this fantastic explanation.
Thanks for your support =)
straight to the point !! thank Ed :)
Please keep uploading, this is great!
That's the plan =)
This lecture awesome ...keep going
Thank you, I will=)
Great, great, great video. Thanks.
If I connected a computer to Hub1 and addressed it with 10.1.2.2/24, would it receive a Local Broadcast (255.255.255.255) from 10.1.1.1? The two machines would be on the same L2 network and on different L3 networks.
Fun question... I would guess Yes, it would receive it. Sounds like something you should lab out =)
😮
Very great video!
Thanks!
Great content. Thank you sir
Excellent video
Thank you very much!
I wanted to ask for some clarification to see if I understand how broadcasts works with ping. It's my understanding that layer 2 broadcasts do not get delivered to the same port where the message originated from. That would mean that when Host1 sent a local broadcast through ping, it would not have received that ping request from itself on the wire (which your demonstration shows). Yet, the ping program shows a response from Host1. So, is it correct to assume that when the ping program recognizes a local broadcast request, it assumes that the user also wants a response from the originating host as well (since it is a part of the local network), so in addition to sending a local broadcast ping request it also sends a self-request (and response) internally? I was just confused because I did not see a broadcast messages delivered to Host1 or a ping response messages from/to Host1 on the wire, which makes sense network-wise but I wanted to know if receiving a response from the originating host was a feature of the ping program itself and not a part of how broadcasts work. Thank you for your video! I hope this question isn't too confusing haha
Awesome!
=)
If I want to ping all the L2 Switches of a single site (whose management IP addresses are in same as Core switch )from core switch of that site , how to execute it ?
If all the management IP's are in the same Subnet, it would be as simple as pinging the directed broadcast IP address of that Subnet. Keep in mind, not all switches respond to broadcast pings by default.
Very informative
Thank you. =)
Hi this is Noor one of your viewers thank you for shooting of such a nice videos, could pleas share how to install GNS3 and let me know about it, I mean could you please make a video on GNS3 installation and setup, how to configure it to function proper.
Hi Noor, glad you enjoyed the video =).
I don't presently have plans for GNS 3 installation videos, but David Bombal has some good resources on the topic:
th-cam.com/users/DavidBombalsearch?query=gns3
What if there had been 5 or more hosts in your ping example? The local broadcast ping only shows 4. If you add a switch (parameter) to ping continuously, would it then do all hosts on the network?
I've tried to replicate the same exact lab using eigrp but im not getting the same ICMP requests for broadcasts any idea why? Also what routing protocol did you use in this lab?
Hi Caesar. I'm fairly certain I just used static routes. Did you enable directed broadcast on all the Router interfaces? What about on the hosts?
Sorry, one other question. So when you sent a local broadcast ping to 255.255.255.255, your demo showed that it was also a Layer 2 broadcast as well. Is that specifically a feature of the ping program? Or are all local IP broadcasts generally sent as layer 2 broadcasts as well? I would have expected a local IP broadcast to be delivered to the MAC address of the router, then the router would translate the message from a unicast frame to a broadcast frame and send it out to the whole network. Although that would mean the router would be delivering the broadcast frame to the same port which it was received. Why is this not the case? I would assume an IP local broadcast would need a router to function properly, yet your demonstration shows that a local IP broadcast frame would be translated to a layer 2 broadcast and not need the router in the first place.
Thanks for the video, it's great!
I'd like to ask you if I have to enable the direct-broadcast option only on the interface connected to the network I want to do the direct broadcast (for example the interface of the ip 10.3.3.3) or to every interface on every router on which the ping will make its way?
I've read your article, thanks!
Excellent question. You only need the `ip directed-broadcast` command on the router interface that would be expected to deliver directed broadcasts. So, in the example of the video it would be on R3's interface with the IP 10.3.3.3 -- the one facing Host 5/6/7.
Glad you enjoyed the video and the article!
In the case of a company's topology that contains branch offices with various subnets and VLANs, can Direct Broadcast be used to troubleshoot connectivity and reachability issues at Layer 2 and Layer 3 levels? If this is one use case, are there other use cases of using Directed Broadcast when troubleshooting issues in modern network topologies? I would think Firewalls, DMZs, Proxy Servers, VPNs, WLANs and WANs are security considerations which will block or drop a Directed Broadcast packet whenever a Directed Broadcast is used as a troubleshooting tool.
You're on the right track... but keep in mind:
(a) Most routers block directed broadcast to limit abuse
(b) Most hosts don't respond to broadcasts by default
So while in theory, you're right about the benefit for troubleshooting. In practice, the two points above would limit the effectiveness of troubleshooting with broadcast packets.
Does this Local Broadcast address, 255.255.255.255, come with a /32 mask?
It sort of doesn't have a mask. It's a single IP, so you could argue it has a /32 mask. But it's somewhat an independent concept from subnet masking.
All your videos are awesome and very helpful to clear core network concept. I am waiting for your course on ipsec and ssl vpn(asa) , bgp on udemy.
Thanks for the kind words, Deepak. =)
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15:30 why the destination will not 10.3.3.127 instead of 255.255.255.255