What is IP Address ::1 ?
Rick Stevens
ricks at nerd.com
Thu Mar 18 16:49:14 UTC 2010
On 3/17/10 7:03 PM, Jonathan Ryshpan wrote:
> Fetchmail produced a number of errors like:
> connection to localhost:smtp [::1/25] failed: Connection
> refused.
> These appeared to be caused by this /etc/hosts file:
> 127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
> ::1 localhost localhost.localdomain localhost6 localhost6.localdomain6
> which has two possible resolutions for localhost, one of which, namely "::1",
> isn't recognized. I attempted to fix things by eliminating the "::1"
> line, to produce the hosts file:
> 127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
> But using this file causes mounts on /media to fail (in my case a
> detachable hard drive and a camera).
> Both problems are cured with this hosts file:
> 127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
> ::1 localhost6 localhost6.localdomain6
>
> All this seems related to IPV6 configuration, but how isn't clear to me.
> Can anyone elucidate? Should I file a bug against the
> original /etc/hosts ?
>
In explanation, "::1" is the IPV6 equivalent of the IPV4 "127.0.0.1". There is nothing
inherently wrong with having two IPs for a given host name (often done in DNS for "DNS
round robin load balancing"), although it's not often done mixing IPV4 and IPV6.
As to why stuff on /mount would fail, that should have nothing to do with networking,
unless the mounts are NFS or Samba mounts.
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