[SOLVED] Not able to ping domain names

tlillenuit · 2019-04-27 16:13:50

While trying to:

$ ping google.com 
PING google.com(dub08s04-in-x0e.1e100.net (2a00:1450:400b:803::200e)) 56 data bytes
From pool-ipv6-pd.agg2.kln.lmk-mlw.eircom.net (2001:bb6:340b:1858::1): icmp_seq=8 Destination unreachable: Address unreachable
From pool-ipv6-pd.agg2.kln.lmk-mlw.eircom.net (2001:bb6:340b:1858::1): icmp_seq=9 Destination unreachable: Address unreachable

But

$ ping 8.8.8.8

PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_seq=1 ttl=54 time=10.1 ms
64 bytes from 8.8.8.8: icmp_seq=2 ttl=54 time=10.5 ms

$ cat /etc/resolv.conf

# Generated by NetworkManager
search home
nameserver 192.168.1.254
nameserver fe80::1%enp0s25

$ ip link 

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: enp0s25: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
    link/ether a0:b3:cc:29:9e:4e brd ff:ff:ff:ff:ff:ff
3: wlo1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN mode DORMANT group default qlen 1000
    link/ether 8c:70:5a:aa:04:ca brd ff:ff:ff:ff:ff:ff

Traceroute and everything else works normally

$ traceroute google.com

traceroute to google.com (216.58.209.110), 30 hops max, 60 byte packets
 1  _gateway (192.168.1.254)  0.439 ms  0.618 ms  0.798 ms
 2  95-44-112-1-dynamic.agg2.kln.lmk-mlw.eircom.net (95.44.112.1)  6.886 ms  17.026 ms  20.620 ms
 3  lag-22.pe1.mlw.lmk-mlw.eircom.net (86.43.10.245)  6.905 ms  6.972 ms  7.233 ms
 4  lag-107-coreb-prp-pe1-mlw.coreb.prp.core.eircom.net (86.43.9.240)  12.518 ms  12.535 ms  12.642 ms
 5  eth-trunk1.hcore1.prp.core.eircom.net (83.174.185.11)  16.099 ms  16.743 ms  16.771 ms
 6  lag-20-br1-6cr-hcore1-prp.br1.6cr.border.eircom.net (86.43.12.215)  13.748 ms  13.011 ms  12.935 ms
 7  72.14.205.72 (72.14.205.72)  12.662 ms  9.794 ms  10.225 ms
 8  74.125.243.209 (74.125.243.209)  11.956 ms  11.921 ms  11.345 ms
 9  209.85.244.231 (209.85.244.231)  12.381 ms  12.352 ms  11.658 ms
10  arn06s07-in-f110.1e100.net (216.58.209.110)  9.852 ms  9.810 ms  10.446 ms

And even ping google.com works normally while connected to VPN, but not without.
What should I be looking next? I want to understand :-)

Normally, I am using NetworkManager to manage my network connections.

Thank you.

Last edited by tlillenuit (2019-04-27 22:14:15)

loqs · 2019-04-27 16:25:28

google.com was resolved to 2a00:1450:400b:803::200e not 8.8.8.8. Does the system have IPV6 internet access?

apollo22 · 2019-04-27 16:34:35

google.com (the search engine) does not resolve to 8.8.8.8 (google's DNS).

Also, "ip addr" result instead of "ip link" result would be more useful

Finally, I think you are trying to resolve an IPV6 address while only being connected to an IPV4 Network, althouth it is weird that your ping resolves to IPV6 while your traceroute resolves to IPV4.

Last edited by apollo22 (2019-04-27 16:38:39)

r0b0t · 2019-04-27 16:39:01

You could use dnscrypt, or set your DNS to 1.1.1.1 , and see if the behavior changes.
The problem is with IPv6, the packet is being dropped somewhere.

Last edited by r0b0t (2019-04-27 16:41:18)

tlillenuit · 2019-04-27 18:55:19

apollo22, I do know google.com ( 209.85.202.x ) and 8.8.8.8 ( one of Google's DNS servers ) are not the same thing.
However, I always ( a habit ) ping 8.8.8.8 and google.com/archlinux.org when I am testing if the connection is alive, to say.

I changed the primary and secondary IPv4 DNS servers in my router to point to Google's DNS servers. I did not
touch the IPv6 DNS configuration there simply because I do not know what sort of setup I could try.

I also changed the IPv4 settings in my NetworkManager configuration
to point to static ones as r0b0t suggested. This combination of tricks seems to have done the trick :-8

Anyway, I want to understand all the aspect of networking mechanisms so I am still trying to figure out what had happened, when, and why.

Loqs, to be honest, I do not know too much about IPv6 configuration as the matter itself is still pretty fresh to me. But my hosts files should be set up to cover IPv6 basic functionality, as far as I understand it. It says:

$ cat /etc/hosts

# Static table lookup for hostnames.
# See hosts(5) for details.
127.0.0.1       localhost
127.0.1.1       t111nemesis
::1             localhost ip6-localhost ip6-loopback
ff00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts

Yeah, baby: 

$ ping -c 3 google.com 
PING google.com(dg-in-x64.1e100.net (2a00:1450:400b:c00::64)) 56 data bytes
64 bytes from dg-in-x64.1e100.net (2a00:1450:400b:c00::64): icmp_seq=1 ttl=49 time=22.8 ms
64 bytes from dg-in-x64.1e100.net (2a00:1450:400b:c00::64): icmp_seq=2 ttl=49 time=22.8 ms
64 bytes from dg-in-x64.1e100.net (2a00:1450:400b:c00::64): icmp_seq=3 ttl=49 time=22.8 ms

--- google.com ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 5ms
rtt min/avg/max/mdev = 22.753/22.774/22.793/0.175 ms

$ nslookup google.com 
Server:         192.168.1.254
Address:        192.168.1.254#53

Non-authoritative answer:
Name:   google.com
Address: 209.85.202.139
Name:   google.com
Address: 209.85.202.101
Name:   google.com
Address: 209.85.202.100
Name:   google.com
Address: 209.85.202.113
Name:   google.com
Address: 209.85.202.138
Name:   google.com
Address: 209.85.202.102
Name:   google.com
Address: 2a00:1450:400b:c01::8b

# NetworkManager Static (Manual) IPv4 DNS configuration:

DNS1: 1.1.1.1
DNS2: 8.8.8.8

Some of the options in my router:

IP Information

IP Protocol Version: IPv4 + IPv6
IPv4 Addressing Type: DHCP
Statis DNS: Enabled
IPv4 Primary DNS: 8.8.8.8
IPv4 Secondary DNS: 8.8.4.4
IPv6 Addressing Type: DHCP
IPv6 Static DNS: Disabled

VDSL WAN-1

Access type: VDSL
IPv4 status: Connected
IPv4 address: 86.40.138.145
IPv4 primary DNS server: 8.8.8.8
IPv4 secondary DNS server: 8.8.4.4
IPv4 default gateway: 86.40.138.1
IPv6 status: Connected
IPv6 address: 2001:bb6:340b:1800:807d:1463:79a2:0/128
IPv6 primary DNS server: 2001:bb0::1
IPv6 secondary DNS server: 2001:bb0::2
IPv6 address prefix list: 2001:bb6:340b:1800::/56


$ [ ip addr 

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    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: enp0s25: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether a0:b3:cc:29:9e:4e brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.3/24 brd 192.168.1.255 scope global dynamic noprefixroute enp0s25
       valid_lft 257709sec preferred_lft 257709sec
    inet6 2001:bb6:340b:1858:63dc:fa6:ee4a:9e50/64 scope global deprecated dynamic noprefixroute 
       valid_lft 6899sec preferred_lft 0sec
    inet6 2001:bb6:340a:a58:3b7:2e11:d262:c90/64 scope global dynamic noprefixroute 
       valid_lft 6945sec preferred_lft 3345sec
    inet6 fe80::aeef:d1c0:700a:ea60/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever
3: wlo1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN group default qlen 1000
    link/ether 9e:c2:08:9b:fe:65 brd ff:ff:ff:ff:ff:ff

Last edited by tlillenuit (2019-04-27 19:05:40)

Lone_Wolf · 2019-04-27 21:34:42

On a ipv6 capable network stack (like archlinux stack) ping tries ipv6 name resoution first , only if that fails will it fallback to ipv4 .
Traceroute appears to default to ipv4 name resolution.

ping comes with iputils, traceroute comes from it's own package.
both have their own upstream, so behaviour differences are expected.

tlillenuit · 2019-04-27 22:13:58

Thanks, Lone_Wolf. That seems to clarify some unusual behaviours of commands, and now I believe I understand the differences in their approaches.

Arch Linux

#1 2019-04-27 16:13:50

[SOLVED] Not able to ping domain names

#2 2019-04-27 16:25:28

Re: [SOLVED] Not able to ping domain names

#3 2019-04-27 16:34:35

Re: [SOLVED] Not able to ping domain names

#4 2019-04-27 16:39:01

Re: [SOLVED] Not able to ping domain names

#5 2019-04-27 18:55:19

Re: [SOLVED] Not able to ping domain names

#6 2019-04-27 21:34:42

Re: [SOLVED] Not able to ping domain names

#7 2019-04-27 22:13:58

Re: [SOLVED] Not able to ping domain names

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