IP Directed Broadcast

[avilt]

I have a 2901K9 router at a remote location. Insite Interface = 10.10.10.1/24 Outside Interface = 20.20.20.1/24

I have set "no ip directed boradcast" on both interfaces. ( I think it's the default settings)

But still when I ping 20.20.20.255 I get a reply from 10.10.10.1

How can I disable this?

[Amjad Abdullah]

I think you need an ACL to disable this.

Modified as wrong info provided. Amjad

Rating useful replies is more useful than saying "Thank you"

[avilt]

That's surprising, then what is the need to run "no ip directed broadcast" command at the interface level?

[turnera]

Directed broadcasts allow a remote device to send a broadcast message to a network segment using a single unicast packet. Once reaching the layer 3 device directly connected to the network for which the broadcast is intended the message is sent as a link-layer broadcast to all hosts on a network segment. The directed broadcast feature is often targeted in a Distributed Denial of Service (DDoS) because a single unicast packet can result in a very large number of replies. The directed broadcast feature should be disabled.

[avilt]

I am aware of ip directed broadcast. My question is why is it not affective inspite of having the command at interface level?

I have a router at the remote location.

Inside Interface = 10.10.10.1/24 Outside Interface = 20.20.20.1/24

I have set "no ip directed boradcast" on both interfaces. ( I think it's the default settings in the latest IOS)

But still when I ping 20.20.20.255 from my location, I get a reply from 10.10.10.1 which is the inside interface of the remote router.

[Amjad Abdullah]

Avilt: I fully mi-understood your question. Ignore my reply above and take the other answer from turnera which is the one describing directed broadcast accurately.
As this is a wireless forum can you move the thread to the appropriate forum so you get better help?


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[avilt]

Can any one provide me the explanation?

I have a router at the remote location.

Inside Interface = 10.10.10.1/24 Outside Interface = 20.20.20.1/24

I have set "no ip directed boradcast" on both interfaces. ( I think it's the default settings in the latest IOS)

But still when I ping 20.20.20.255 from my location (remotely), I get a reply from 10.10.10.1 which is the inside interface of the remote router.

[Richard Burts]

The answer requires a correct understanding of what the command is intended to do. The command is intended to prevent receiving a packet with destination of broadcast address and forwarding it as a broadcast onto the local subnet. The command is working as intended since the packet is not forwarded. What you are observing is the router, acting as a host, responding to the packet but not forwarding the packet.

HTH

Rick

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