IPv6 get alive hosts without ICMPv6?

Question

How would you probe the first few ports on TCP/UDP to see the host is alive like Angryipscanner but only on ipv6?Too see if the hosts are alive without ICMPv6?I am on Windows.

Answer 1

Technically speaking, host can be "alive" (define alive?) without replying to ICMP ping requests. E.g. you can block ICMPv4 and ICMPv6 traffic in the firewall (selectively, still allowing the crucial things like PMTU discovery), without any adverse effects.

Same thing with TCP connection attempts. If you're trying to connect to a random port, you can get 3 different results:

1. Connection successful. Host is alive.

2. Connection refused. Host is alive.

3. Connection times out. Host is either offline, or blocks connection attempts on that port, or connection failed because of some other networking problem.

How can you discriminate between 3 different possibilities in #3?

Method to "ping" via TCP or UDP

You can "coerce" traceroute to make kind of "ping" via TCP or UDP:

traceroute -6 -f 30 -T ipv6.google.com

traceroute to ipv6.google.com (2001:4860:8005::69), 30 hops max, 80 byte packets
30 pz-in-x69.1e100.net (2001:4860:8005::69) 87.299 ms 87.257 ms 87.208 ms

Same request, only via UDP will fail:

traceroute -6 -f 30 -U ipv6.google.com

traceroute to ipv6.google.com (2001:4860:8005::63), 30 hops max, 80 byte packets
30 * * *

You'll only need to pipe the results to grep, if you need this in a script.