Tuesday, 17 July 2012

Ping multicast address , RFC for Multicast

Anytime did u try to ping any multicast address ?

What will happen if I ping to multicast IP lets say 224.1.1.1?

Multicast addresses are in the range of 224.0.0.0 through 239.255.255.255.

The IANA registry talks about these multicast address.

http://www.iana.org/assignments/multicast-addresses/multicast-addresses.xml

It is defined in RFC 1112.

As per IANA

"The range of addresses between 224.0.0.0 and 224.0.0.255, inclusive, is reserved for the use of routing protocols and other low-level topology discovery or maintenance protocols, such as gateway discovery and group membership reporting.  Multicast routers should not forward any multicast datagram with destination addresses in this range, regardless of its TTL. "

OK so now main question , when you ping to multicast address how ARP gets resolved ?

Well , if you go through RFC 1112 , you will come to know that for multicast ip- mac address mapping is done at local network interface itself. It wont be done at IP or ARP layers but at Ethernet layer itself.

So if you ping to this address there wont be any ARP request generated but directly ICMP ECHO request packet will be generated by the PC and will be sent with Ethernet 2 -MAC address as 01:00:5E:01:01:01.

Don't Trust me Test it !!!


Keep learning and Keep Sharing !!!


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