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#1 2013-05-20 00:38:53

anatolik
Developer
Registered: 2012-09-27
Posts: 387

DHCP and home network - cannot resolve some machine names

Hi,

I have following network configuration at home:
- Home router installed by my internet provider (ATT) - 2Wire 3600HGV. It also acts as a local nameserver.
- Machine #1, with wired ethernet
- Machine #2, both with wired and wireless ethernet

Previously Machine #1 used dynamic IP configured by systemd dhcpcd@service as described in [1]. Machine #2 previously used NetworkManager applet from GnomeShell and configured as dhcp as well.

Previously I was able to 'ping machine1' but 'ping machine2' has failed. Machine2 name was visible at HomeRouter web page, but was not pingable. That was really odd. I thought that the problem could be because NetworkManager. So I changed both machines to configure its network by netctl. Both machines have similar config:

$ cat /etc/netctl/ethernet 
Description='A basic dhcp ethernet connection'
Interface=enp4s0
Connection=ethernet

Machine 2 uses 'multiple interfaces' configuration as described in [2].

Also both machines have the same resolv.conf file

$ cat /etc/resolv.conf 
# Generated by resolvconf
domain gateway.2wire.net
nameserver 192.168.1.254

Here is network interface information for machine1:

$ ip a
......
2: enp4s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether bc:5f:f4:32:e0:2d brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.81/24 brd 192.168.1.255 scope global enp4s0
       valid_lft forever preferred_lft forever
    inet6 fe80::be5f:f4ff:fe32:e02d/64 scope link 
       valid_lft forever preferred_lft forever

and this is for machine2

$ ip a
....
2: enp14s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000
    link/ether 00:1f:29:00:19:72 brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.77/24 brd 192.168.1.255 scope global enp14s0
       valid_lft forever preferred_lft forever
    inet6 fe80::21f:29ff:fe00:1972/64 scope link 
       valid_lft forever preferred_lft forever
3: wls4: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000
    link/ether 00:21:5c:5c:06:41 brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.72/24 brd 192.168.1.255 scope global wls4
       valid_lft forever preferred_lft forever
    inet6 fe80::221:5cff:fe5c:641/64 scope link 
       valid_lft forever preferred_lft forever

So after I changed network config to netctl now machine2 name can be resolved, BUT now I cannot resolve machine1 name!!! I can ping IP address but not the name.

$ ping machine1
ping: unknown host machine1
$ ping 192.168.1.81
PING 192.168.1.81 (192.168.1.81) 56(84) bytes of data.
64 bytes from 192.168.1.81: icmp_seq=1 ttl=64 time=0.130 ms

the same for machine2 works fine

$ ping machine2
PING machine2.gateway.2wire.net (192.168.1.77): 56 data bytes
64 bytes from 192.168.1.77: icmp_seq=0 ttl=64 time=1.761 ms

I can access internet from both machines. Internet works fine, the problem only with name for machine1.

So the question - what the problem can be? How to debug this kind of issues? Is it dhcpcd issue, or router?


[1] https://wiki.archlinux.org/index.php/Ne … figuration
[2] https://wiki.archlinux.org/index.php/Netctl

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#2 2013-05-25 20:24:58

anatolik
Developer
Registered: 2012-09-27
Posts: 387

Re: DHCP and home network - cannot resolve some machine names

Initially router (dns server) did not resolve the machine1 name correctly. It returned error on

$ dig machine1

After some period of time the issue has been resolved "by itself". Now both

$ dig machine1
$ dig machine2

work fine. The case is closed. I do not know what happened but I blame my router.

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