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linux - Ping to IPv4 works but IPv6 does not

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:  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:  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:  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:  mtu 1500 qdisc noop state DOWN group default qlen 100

    link/void 
5: tunl0@NONE:  mtu 1480 qdisc noop state DOWN group default qlen 1
    link/ipip 0.0.0.0 brd 0.0.0.0
6: gre0@NONE:  mtu 1476 qdisc noop state DOWN group default qlen 1
    link/gre 0.0.0.0 brd 0.0.0.0
7: gretap0@NONE:  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:  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:  mtu 1500 qdisc noop state DOWN group default qlen 1

    link/tunnel6 :: brd ::
10: sit0@NONE:  mtu 1480 qdisc noop state DOWN group default qlen 1
    link/sit 0.0.0.0 brd 0.0.0.0
11: ip6tnl0@NONE:  mtu 1452 qdisc noop state DOWN group default qlen 1
    link/tunnel6 :: brd ::
12: ip6gre0@NONE:  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.

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