I have a hosted VPS running on arch linux. I'm trying to make outgoing connections from this server, but all of them fail. After a little bit of debugging, I figured that the reason for failed connections is that my server cannot access IPv6 addresses. Ping to IPv4 addresses work, but not to IPv6. Here is a sample.
[root@li863-18 /]# nslookup google.com
Server: 103.3.60.20
Address: 103.3.60.20#53
Non-authoritative answer:
Name: google.com
Address: 74.125.68.100
Name: google.com
Address: 74.125.68.102
Name: google.com
Address: 74.125.68.113
Name: google.com
Address: 74.125.68.139
Name: google.com
Address: 74.125.68.138
Name: google.com
Address: 74.125.68.101
Name: google.com
Address: 2404:6800:4003:c02::8a
[root@li863-18 /]# ping 74.125.68.100
PING 74.125.68.100 (74.125.68.100) 56(84) bytes of data.
64 bytes from 74.125.68.100: icmp_seq=1 ttl=50 time=1.20 ms
64 bytes from 74.125.68.100: icmp_seq=2 ttl=50 time=1.32 ms
64 bytes from 74.125.68.100: icmp_seq=3 ttl=50 time=1.41 ms
^C
--- 74.125.68.100 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2003ms
rtt min/avg/max/mdev = 1.200/1.311/1.414/0.097 ms
[root@li863-18 /]#
[root@li863-18 /]# ping 2404:6800:4003:c02::8a
PING 2404:6800:4003:c02::8a(2404:6800:4003:c02::8a) 56 data bytes
^C
--- 2404:6800:4003:c02::8a ping statistics ---
7 packets transmitted, 0 received, 100% packet loss, time 6070ms
My networking configuration. I've run the commands ip a s, ip -6 r s and cat /etc/resolv.conf:
[root@li863-18 /]# ip a s
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: dummy0: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default qlen 1000
link/ether ea:46:ac:25:5b:a3 brd ff:ff:ff:ff:ff:ff
inet6 fe80::99c7:bfde:3127:700c/64 scope link
valid_lft forever preferred_lft forever
3: ens4: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
link/ether f2:3c:91:e4:50:68 brd ff:ff:ff:ff:ff:ff
inet 139.162.21.18/24 brd 139.162.21.255 scope global ens4
valid_lft forever preferred_lft forever
inet6 2400:8901::f914:4433:e826:6f2a/64 scope global mngtmpaddr noprefixroute dynamic
valid_lft 2592000sec preferred_lft 604800sec
inet6 fe80::f03c:91ff:fee4:5068/64 scope link
valid_lft forever preferred_lft forever
4: teql0: <NOARP> mtu 1500 qdisc noop state DOWN group default qlen 100
link/void
5: tunl0@NONE: <NOARP> mtu 1480 qdisc noop state DOWN group default qlen 1
link/ipip 0.0.0.0 brd 0.0.0.0
6: gre0@NONE: <NOARP> mtu 1476 qdisc noop state DOWN group default qlen 1
link/gre 0.0.0.0 brd 0.0.0.0
7: gretap0@NONE: <BROADCAST,MULTICAST> mtu 1462 qdisc noop state DOWN group default qlen 1000
link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff
8: ip_vti0@NONE: <NOARP> mtu 1428 qdisc noop state DOWN group default qlen 1
link/ipip 0.0.0.0 brd 0.0.0.0
9: ip6_vti0@NONE: <NOARP> mtu 1500 qdisc noop state DOWN group default qlen 1
link/tunnel6 :: brd ::
10: sit0@NONE: <NOARP> mtu 1480 qdisc noop state DOWN group default qlen 1
link/sit 0.0.0.0 brd 0.0.0.0
11: ip6tnl0@NONE: <NOARP> mtu 1452 qdisc noop state DOWN group default qlen 1
link/tunnel6 :: brd ::
12: ip6gre0@NONE: <NOARP> mtu 1448 qdisc noop state DOWN group default qlen 1
link/gre6 00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00 brd 00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00
[root@li863-18 /]# ip -6 r s
2400:8901::/64 dev ens4 proto kernel metric 203 mtu 1500 pref medium
fe80::/64 dev ens4 proto kernel metric 256 pref medium
fe80::/64 dev dummy0 proto kernel metric 256 pref medium
default via fe80::1 dev ens4 metric 203 mtu 1500 pref medium
[root@li863-18 /]# cat /etc/resolv.conf
# Generated by resolvconf
domain members.linode.com
nameserver 103.3.60.20
nameserver 139.162.11.5
nameserver 139.162.13.5
Adding traceroute info.
[root@li863-18 /]# traceroute google.com
traceroute to google.com (74.125.68.138), 30 hops max, 60 byte packets
1 103.3.60.3 (103.3.60.3) 0.711 ms 0.936 ms 1.085 ms
2 139.162.0.9 (139.162.0.9) 0.638 ms 0.654 ms 139.162.0.13 (139.162.0.13) 0.606 ms
3 15169.sgw.equinix.com (27.111.228.30) 0.827 ms 0.826 ms 0.820 ms
4 108.170.242.66 (108.170.242.66) 1.074 ms 108.170.243.19 (108.170.243.19) 1.122 ms 108.170.240.226 (108.170.240.226) 1.107 ms
5 209.85.243.215 (209.85.243.215) 1.440 ms 209.85.243.241 (209.85.243.241) 20.269 ms 108.170.240.173 (108.170.240.173) 1.702 ms
6 209.85.255.217 (209.85.255.217) 7.835 ms 216.239.51.61 (216.239.51.61) 1.884 ms 209.85.243.209 (209.85.243.209) 1.532 ms
7 216.239.48.73 (216.239.48.73) 4.784 ms 216.239.51.61 (216.239.51.61) 2.075 ms *
8 * * *
9 * * *
10 * * *
11 * * *
12 * * *
13 * * *
14 * * *
15 * sc-in-f138.1e100.net (74.125.68.138) 1.490 ms 1.653 ms
[root@li863-18 /]# traceroute 74.125.68.138
traceroute to 74.125.68.138 (74.125.68.138), 30 hops max, 60 byte packets
1 103.3.60.3 (103.3.60.3) 0.889 ms 0.868 ms 1.311 ms
2 139.162.0.9 (139.162.0.9) 0.709 ms 139.162.0.13 (139.162.0.13) 0.650 ms 139.162.0.9 (139.162.0.9) 0.687 ms
3 139.162.0.18 (139.162.0.18) 0.658 ms 15169.sgw.equinix.com (27.111.228.30) 0.727 ms 139.162.0.18 (139.162.0.18) 0.625 ms
4 15169.sgw.equinix.com (27.111.228.30) 0.715 ms 108.170.240.226 (108.170.240.226) 1.488 ms 108.170.240.162 (108.170.240.162) 6.201 ms
5 108.170.240.236 (108.170.240.236) 1.202 ms 108.170.242.71 (108.170.242.71) 1.114 ms 216.239.42.47 (216.239.42.47) 1.688 ms
6 209.85.255.80 (209.85.255.80) 3.119 ms 209.85.243.241 (209.85.243.241) 2.212 ms 209.85.242.221 (209.85.242.221) 1.597 ms
7 209.85.255.80 (209.85.255.80) 7.597 ms 1.422 ms 72.14.236.130 (72.14.236.130) 10.235 ms
8 * * *
9 * * *
10 * * *
11 * * *
12 * * *
13 * * *
14 * * *
15 * sc-in-f138.1e100.net (74.125.68.138) 1.869 ms 1.878 ms
[root@li863-18 /]# traceroute 2404:6800:4003:c02::64
traceroute to 2404:6800:4003:c02::64 (2404:6800:4003:c02::64), 30 hops max, 80 byte packets
1 * * *
2 * * *
3 * * *
4 * * *
5 * * *
6 * * *
7 * * *
8 * * *
9 * * *
10 * * *
11 * * *
12 * * *
13 * * *
14 * * *
15 * * *
16 * * *
17 * * *
18 * * *
19 * * *
20 * * *
21 * * *
22 * * *
23 * * *
24 * * *
25 * * *
26 * * *
27 * * *
28 * * *
29 * * *
30 * * *
Any pointer as to why this is the case. I would not want to disable IPv6 addresses through kernel unless absolutely necessary.
Best Answer
It appears you are trying to use a privacy address (RFC 3972, RFC 4941, or RFC 7217) in a
/64which Linode is sharing among multiple customers.By default a Linode machine is allocated a single IPv6 address based on their MAC address inside a link
/64shared between all customers in the datacenter. Linode have taken steps to protect against IP spoofing. This means you won't even see neighbor discovery packets for other IP addresses in the segment than your own.For that reason privacy addresses are not going to work. Try instead to use an IPv6 address based on your MAC address. In your case the IPv6 address would be
2400:8901::f03c:91ff:fee4:5068If you need more than one address you can file a ticket to request a routed
/64which is not going to be shared.