Network & Broadcast pinging

[Anand Narayana]

Hi,

i could able to ping 10.2.1.0 & ofcourse broadcast can ping 10.2.1.255. so is it normal r something probz went wrong like looping?

[vladrac-ccna]

Could you please reformulate your question?

Its ok to ping broadcast and get response from all host on the same broadcast domain.

Let us know,

vlad

[Anand Narayana]

k i will make you clear in my question,

network 10.2.1.0

broadcast 10.2.1.255

subnet 255.255.255.0

clients ip address 10.2.1.1 to 10.2.1.254

from any of the client machine, i could able to ping 10.2.1.0, is that behaviour is normal r something went wrong?

c:\ping 10.2.1.0

pingging 10.2.1.0 with 32 bytes of data:

Reply from 10.2.1.0: bytes=32 time<10ms TTL=255

Reply from 10.2.1.0: bytes=32 time<10ms TTL=255

Reply from 10.2.1.0: bytes=32 time<10ms TTL=255

Reply from 10.2.1.0: bytes=32 time<10ms TTL=255

[tdrais]

Some devices will respond to pings to the network address which is what you are pinging and some will respond to pings on the broadcast address. These devices are designed to do this.

You can also get a ping response from 224.0.0.1 since many devices for unkown reasons have mutlicast on even when they are not doing any multicast or routing.

If this is a good thing or a bad thing is discussed many times. A smurf attack uses this issue to attack a network.

[Anand Narayana]

with your response can i assume that the behaviour is normal & not any other issue like loop r device probz?

[vladrac-ccna]

Yes, no need to worry.

vlad

[vladrac-ccna]

Not sure what kind of anwswer you were expecting.

But ok.

Unless you are getting responses from other subnet outside the broadcast domain, you can be sure that there's no loop issue on your network.

vlad

[Richard Burts]

As Tim has pointed out it is normal behavior if you ping to the network address or to the network broadcast address of the local subnet that you may get answers. Cisco routers generally do generate responses to .0 and .255 addresses (note that some early implementations used .0 as the broadcast address - I believe that this is why Cisco generates a response).

Vlad points out that there is some difference whether we are pinging to addresses of the local subnet (the network address or network broadcast address) or to addresses outside the local subnet. If we are pinging to addresses outside the local subnet then what happens depends on how the remote router is configured: if the router interface is configured with ip directed-broadcast then the router does forward the packet and we may get responses from devices within the remote subnet. But if the remote router is configured with no ip directed-broadcast then it does not forward the packet. (The last time I tested this the remote router did generate a response to the ping even though it did not forward onto the remote subnet.)

So certainly it is normal behavior if you ping the address within the local subnet and get a response.

HTH

Rick