IPv6 security myth – IPv6 network/host are too big to scan

Posted by crimsonpisang on   0 comments   0 trackback

An IPv6 /64 allows for up to 18,446,744,073,709,551,616 (about 18.4 Quintillion) host addresses. To take that into perspective, if a computer could scan a billion addresses per second, it would take about 585 years to complete.

Fortunately there are a couple of ways to find all the host without having the need to scan the entire address space.
In IPv6, multicast address were used instead of broadcast. One way is to use multicast group, FF02:: Link Local prefix. When an active device connected to the network, it would joined the FF02::1 multicast group. This group, the All Nodes, is the equivalent to the broadcast address used in IPv4 mainly used for ARP.
Simply by pinging the All node multicast address, we could get a reply for all active nodes on the network in just a few seconds.

Host Sweep

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