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TOPIC: Ping Oddity with multicast

Ping Oddity with multicast 9 years 10 months ago #18344

  • Starfire
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In my ccna studies I am going through protocol headers and the structure of the packets flying around. I have been looking at multicasts and I am confused as to what is happening here:

>Ping 224.0.0.1 (“Everyone on this subnet” according to iana - http://www.iana.org/assignments/multicast-addresses)
request timed out. (X 4)

However, when capturing the traffic with Ethereal/Wireshark I get the following.

x.x.x.72 224.0.0.1 ICMP Echo (ping) request
x.x.x.5 x.x.x.72 ICMP Echo (ping) reply
x.x.x.19 x.x.x.72 ICMP Echo (ping) reply
x.x.x.13 x.x.x.72 ICMP Echo (ping) reply
x.x.x.10 x.x.x.72 ICMP Echo (ping) reply
x.x.x.9 x.x.x.72 ICMP Echo (ping) reply
x.x.x.18 x.x.x.72 ICMP Echo (ping) reply
x.x.x.14 x.x.x.72 ICMP Echo (ping) reply
x.x.x.12 x.x.x.72 ICMP Echo (ping) reply
x.x.x.17 x.x.x.72 ICMP Echo (ping) reply
x.x.x.11 x.x.x.72 ICMP Echo (ping) reply
x.x.x.15 x.x.x.72 ICMP Echo (ping) reply

Is it just overloading the ping application. I would have thought the ping would have resulted with "reply from x.x.x.5" at least.

Still, I never knew you could multi-ping
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Re: Ping Oddity with multicast 9 years 10 months ago #18352

  • havohej
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thats why you are multicast pinging (think as brodcast)
the 224.0.0.1 means to the all multicats enabled devices (routers running certain routing protocols, switches, servers, end devices)
so when you ping to the 224.0.0.1 all mentioned devices with multicast enabled software will respond, thats why you see more devices.

I have also pinged 224.0.0.1 first by my end device and also in my default gateway, In the first it answers me a multicast server, in the second it answers me all multicast enables local devices (routers, switches, servers) connected to its local interfaces.
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Re: Ping Oddity with multicast 9 years 10 months ago #18365

  • S0lo
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I would have thought the ping would have resulted with "reply from x.x.x.5" at least.

And it did reply, didn't it ?

But, A question remains, What MAC address does it use to send it ?

In my trace it uses 01:00:5E:xx:xx:xx

were xx:xx:xx seams to have the exact last three octets of the IP that was pinged. So if I ping 224.6.3.2, The destination MAC of the packets sent would have 01:00:5E:06:03:2.

Why ? :roll: no idea

Usually a broadcast would have FF:FF:FF:FF:FF:FF MAC as far as I know.
Studying CCNP...

Ammar Muqaddas
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