Re: ipv6 gateway on different subnet

Here's the results from Debian.

sudo ip -6 addr add 2602:fed2:7116:d82c::d/64 dev eth0
sudo tcpdump -npi vioif0 -vw icmp6.pcap icmp6

from the same home cpu
ping6 -c2 -t5 2602:fed2:7116:d82c::d 
PING(56=40+8+8 bytes) 2600:1700:7960:9a70:a280:69ff:fef4:24f --> 2602:fed2:7116:d82c::d
16 bytes from 2602:fed2:7116:d82c::d, icmp_seq=1 hlim=56 time=11.643 ms

--- 2602:fed2:7116:d82c::d ping statistics ---
2 packets transmitted, 1 packets received, 50.0% packet loss
round-trip min/avg/max/stddev = 11.643/11.643/11.643/0.000 ms

Here's the tcpdump info

reading from file 17.pcap, link-type EN10MB (Ethernet), snapshot length 262144
18:24:32.110358 d8:67:d9:58:3d:1b > 33:33:ff:00:00:00, ethertype IPv6 (0x86dd), length 86: (class 0xe0, hlim 255, next-header ICMPv6 (58) payload length: 32) fe80::da67:d9ff:fe58:3d1b > ff02::1:ff00:0: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2604:f440:3:17::
	  source link-address option (1), length 8 (1): d8:67:d9:58:3d:1b
18:24:32.230028 d8:67:d9:58:3d:1b > 33:33:ff:00:00:01, ethertype IPv6 (0x86dd), length 86: (class 0xe0, hlim 255, next-header ICMPv6 (58) payload length: 32) fe80::da67:d9ff:fe58:3d1b > ff02::1:ff00:1: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2602:2c8:0:103f::1
	  source link-address option (1), length 8 (1): d8:67:d9:58:3d:1b
18:24:32.405109 d8:67:d9:58:3d:1b > 33:33:ff:00:00:01, ethertype IPv6 (0x86dd), length 86: (class 0xe0, hlim 255, next-header ICMPv6 (58) payload length: 32) fe80::da67:d9ff:fe58:3d1b > ff02::1:ff00:1: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2602:2c8:0:1027::1
	  source link-address option (1), length 8 (1): d8:67:d9:58:3d:1b
18:24:33.227600 d8:67:d9:58:3d:1b > 00:16:3e:d7:cf:50, ethertype IPv6 (0x86dd), length 70: (hlim 250, next-header ICMPv6 (58) payload length: 16) 2600:1700:7960:9a70:a280:69ff:fef4:24f > 2602:fed2:7116:d82c::d: [icmp6 sum ok] ICMP6, echo request, id 29723, seq 0
18:24:33.227653 00:16:3e:d7:cf:50 > 33:33:ff:00:00:01, ethertype IPv6 (0x86dd), length 86: (hlim 255, next-header ICMPv6 (58) payload length: 32) fe80::216:3eff:fed7:cf50 > ff02::1:ff00:1: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2602:fed2:7116::1
	  source link-address option (1), length 8 (1): 00:16:3e:d7:cf:50
18:24:33.345667 00:16:3e:85:d4:98 > 33:33:ff:00:00:01, ethertype IPv6 (0x86dd), length 86: (hlim 255, next-header ICMPv6 (58) payload length: 32) 2602:2c8:0:1010::1 > ff02::1:ff00:1: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2602:2c8::1
	  source link-address option (1), length 8 (1): 00:16:3e:85:d4:98
18:24:33.502068 d8:67:d9:58:3d:1b > 33:33:ff:00:00:01, ethertype IPv6 (0x86dd), length 86: (class 0xe0, hlim 255, next-header ICMPv6 (58) payload length: 32) fe80::da67:d9ff:fe58:3d1b > ff02::1:ff00:1: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2602:2c8:0:1027::1
	  source link-address option (1), length 8 (1): d8:67:d9:58:3d:1b
18:24:33.706212 d8:67:d9:58:3d:1b > 33:33:ff:00:00:03, ethertype IPv6 (0x86dd), length 86: (class 0xe0, hlim 255, next-header ICMPv6 (58) payload length: 32) fe80::da67:d9ff:fe58:3d1b > ff02::1:ff00:3: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2602:fed2:7116:112::3
	  source link-address option (1), length 8 (1): d8:67:d9:58:3d:1b
18:24:34.120030 d8:67:d9:58:3d:1b > 33:33:ff:00:00:03, ethertype IPv6 (0x86dd), length 86: (class 0xe0, hlim 255, next-header ICMPv6 (58) payload length: 32) fe80::da67:d9ff:fe58:3d1b > ff02::1:ff00:3: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2602:fed2:7116:112::3
	  source link-address option (1), length 8 (1): d8:67:d9:58:3d:1b
18:24:34.275637 d8:67:d9:58:3d:1b > 00:16:3e:d7:cf:50, ethertype IPv6 (0x86dd), length 70: (hlim 250, next-header ICMPv6 (58) payload length: 16) 2600:1700:7960:9a70:a280:69ff:fef4:24f > 2602:fed2:7116:d82c::d: [icmp6 sum ok] ICMP6, echo request, id 29723, seq 1
18:24:34.275666 00:16:3e:d7:cf:50 > 33:33:ff:00:00:01, ethertype IPv6 (0x86dd), length 86: (hlim 255, next-header ICMPv6 (58) payload length: 32) 2602:fed2:7116:d82c::d > ff02::1:ff00:1: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2602:fed2:7116::1
	  source link-address option (1), length 8 (1): 00:16:3e:d7:cf:50
18:24:34.277369 d8:67:d9:58:3d:1b > 00:16:3e:d7:cf:50, ethertype IPv6 (0x86dd), length 86: (class 0xe0, hlim 255, next-header ICMPv6 (58) payload length: 32) 2602:fed2:7116::1 > 2602:fed2:7116:d82c::d: [icmp6 sum ok] ICMP6, neighbor advertisement, length 32, tgt is 2602:fed2:7116::1, Flags [router, solicited, override]
	  destination link-address option (2), length 8 (1): d8:67:d9:58:3d:1b
18:24:34.277388 00:16:3e:d7:cf:50 > d8:67:d9:58:3d:1b, ethertype IPv6 (0x86dd), length 70: (flowlabel 0x1bacc, hlim 64, next-header ICMPv6 (58) payload length: 16) 2602:fed2:7116:d82c::d > 2600:1700:7960:9a70:a280:69ff:fef4:24f: [icmp6 sum ok] ICMP6, echo reply, id 29723, seq 1
18:24:34.364779 00:16:3e:22:cb:ef > 33:33:ff:00:00:01, ethertype IPv6 (0x86dd), length 86: (hlim 255, next-header ICMPv6 (58) payload length: 32) 2602:2c8:0:288f::1 > ff02::1:ff00:1: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2602:2c8::1
	  source link-address option (1), length 8 (1): 00:16:3e:22:cb:ef
18:24:34.552558 d8:67:d9:58:3d:1b > 33:33:ff:00:00:01, ethertype IPv6 (0x86dd), length 86: (class 0xe0, hlim 255, next-header ICMPv6 (58) payload length: 32) fe80::da67:d9ff:fe58:3d1b > ff02::1:ff00:1: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2602:2c8:0:103f::1
	  source link-address option (1), length 8 (1): d8:67:d9:58:3d:1b
18:24:35.096034 d8:67:d9:58:3d:1b > 33:33:ff:00:00:00, ethertype IPv6 (0x86dd), length 86: (class 0xe0, hlim 255, next-header ICMPv6 (58) payload length: 32) fe80::da67:d9ff:fe58:3d1b > ff02::1:ff00:0: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2604:f440:3:17::
	  source link-address option (1), length 8 (1): d8:67:d9:58:3d:1b
18:24:40.268263 d8:67:d9:58:3d:1b > 33:33:ff:00:00:06, ethertype IPv6 (0x86dd), length 86: (class 0xe0, hlim 255, next-header ICMPv6 (58) payload length: 32) fe80::da67:d9ff:fe58:3d1b > ff02::1:ff00:6: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2602:2c8::6
	  source link-address option (1), length 8 (1): d8:67:d9:58:3d:1b
18:24:41.147660 d8:67:d9:58:3d:1b > 33:33:ff:00:00:03, ethertype IPv6 (0x86dd), length 86: (class 0xe0, hlim 255, next-header ICMPv6 (58) payload length: 32) fe80::da67:d9ff:fe58:3d1b > ff02::1:ff00:3: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2602:2c8::3
	  source link-address option (1), length 8 (1): d8:67:d9:58:3d:1b
18:24:42.148197 d8:67:d9:58:3d:1b > 33:33:ff:00:00:03, ethertype IPv6 (0x86dd), length 86: (class 0xe0, hlim 255, next-header ICMPv6 (58) payload length: 32) fe80::da67:d9ff:fe58:3d1b > ff02::1:ff00:3: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2602:2c8::3
	  source link-address option (1), length 8 (1): d8:67:d9:58:3d:1b


Comparing these lines on Debian.

18:24:34.275637 d8:67:d9:58:3d:1b > 00:16:3e:d7:cf:50, ethertype IPv6 (0x86dd), length 70: (hlim 250, next-header ICMPv6 (58) payload length: 16) 2600:1700:7960:9a70:a280:69ff:fef4:24f > 2602:fed2:7116:d82c::d: [icmp6 sum ok] ICMP6, echo request, id 29723, seq 1
18:24:34.275666 00:16:3e:d7:cf:50 > 33:33:ff:00:00:01, ethertype IPv6 (0x86dd), length 86: (hlim 255, next-header ICMPv6 (58) payload length: 32) 2602:fed2:7116:d82c::d > ff02::1:ff00:1: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2602:fed2:7116::1
	  source link-address option (1), length 8 (1): 00:16:3e:d7:cf:50
18:24:34.277369 d8:67:d9:58:3d:1b > 00:16:3e:d7:cf:50, ethertype IPv6 (0x86dd), length 86: (class 0xe0, hlim 255, next-header ICMPv6 (58) payload length: 32) 2602:fed2:7116::1 > 2602:fed2:7116:d82c::d: [icmp6 sum ok] ICMP6, neighbor advertisement, length 32, tgt is 2602:fed2:7116::1, Flags [router, solicited, override]
	  destination link-address option (2), length 8 (1): d8:67:d9:58:3d:1b
18:24:34.277388 00:16:3e:d7:cf:50 > d8:67:d9:58:3d:1b, ethertype IPv6 (0x86dd), length 70: (flowlabel 0x1bacc, hlim 64, next-header ICMPv6 (58) payload length: 16) 2602:fed2:7116:d82c::d > 2600:1700:7960:9a70:a280:69ff:fef4:24f: [icmp6 sum ok] ICMP6, echo reply, id 29723, seq 1

VS.
These on NetBSD

08:47:12.201801 d8:67:d9:58:3d:1b > 33:33:ff:00:00:0c, ethertype IPv6 (0x86dd), length 86: (class 0xe0, hlim 255, next-header ICMPv6 (58) payload length: 32) fe80::da67:d9ff:fe58:3d1b > ff02::1:ff00:c: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2602:fed2:7116:d82c::c
	  source link-address option (1), length 8 (1): d8:67:d9:58:3d:1b
08:47:12.201844 00:16:3e:d7:cf:50 > d8:67:d9:58:3d:1b, ethertype IPv6 (0x86dd), length 86: (hlim 255, next-header ICMPv6 (58) payload length: 32) fe80::216:3eff:fed7:cf50 > fe80::da67:d9ff:fe58:3d1b: [icmp6 sum ok] ICMP6, neighbor advertisement, length 32, tgt is 2602:fed2:7116:d82c::c, Flags [solicited, override]
	  destination link-address option (2), length 8 (1): 00:16:3e:d7:cf:50

I don't see the echo request or reply on NetBSD, which I guess is showing that ping is failing.

Debian the request comes from my vps to the router, the router replies and theres a 'router' flag
2602:fed2:7116:d82c::d > ff02::1:ff00:1: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2602:fed2:7116::1
2602:fed2:7116::1 > 2602:fed2:7116:d82c::d: [icmp6 sum ok] ICMP6, neighbor advertisement, length 32, tgt is 2602:fed2:7116::1, Flags [router, solicited, override]

NetBSD seems to be going the other direction. Assuming this because the router is trying to find my server to send the echo request to it.
fe80::da67:d9ff:fe58:3d1b > ff02::1:ff00:c: [icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has 2602:fed2:7116:d82c::c
fe80::216:3eff:fed7:cf50 > fe80::da67:d9ff:fe58:3d1b: [icmp6 sum ok] ICMP6, neighbor advertisement, length 32, tgt is 2602:fed2:7116:d82c::c, Flags [solicited, override]


That's about the extent of my debugging skills here. I hope someone else sees more from this.