/etc/hosts - how does that file work?? - was weird nfs issues.

[Tim Judd]

On 6/4/09, Peter <fbsdq at peterk.org> wrote:
>> On Thursday 04 June 2009 20:48:21 Peter wrote:
>>> iH,
>>>   This all started with NFS not mounting at boot....so, testing in VMs:
>>
>> <snip>
>>
>>> Why is ping using one IP, and ssh/mount_nfs/showmount using another IP
> from /etc/hosts?
>>
>> Q: Where is described that name resolution for A or PTR records should
> be
>> returned in a fixed order and that a consumer should always use the
> first
>> one
>> returned?
>> A: Nowhere. Name servers are encouraged to do round-robin returns if not
> specified otherwise. Applications may sort/pick at their own leisure.
>>
>> --
>> Mel
>
> I do not think /etc/hosts does round robin, I always assumed first match
> wins...DNS/bind I would understand...
>
> Why does ping always return the 172.20.6.1 address,
>  and ftp,nc,ssh,telnet,fetch _always_ uses the 116 address?
>
> I would assume at least sometimes it would hit the 172 address with
> anything besides ping - but it only ping hits the 172 address...
> If so, I'd guess there would be consistency between ping lookups and
> 'telnet/ssh/etc' lookups...
>
> Why if the 116.23.45.3 last octet is bumped up, everything _always_
> returns the 172 address?
>
> client# grep server /etc/hosts
> 172.20.6.1              server.test server
> 116.23.45.5             server.test server
> client# telnet server
> Trying 172.20.6.1...
> telnet: connect to address 172.20.6.1: Connection refused
> Trying 116.23.45.5...
>
> /etc/hosts - 'server' changed to
> 116.23.45.3:
>
> client# telnet server
> Trying 116.23.45.3...
> telnet: connect to address 116.23.45.3: Operation timed out
> Trying 172.20.6.1...
> telnet: connect to address 172.20.6.1: Connection refused
> telnet: Unable to connect to remote host
>
> if server has ip>116.23.45.3, it always uses the 172 address first...
>
> but ping always uses the  172...
> even if third entry is added into /etc/hosts - nothing ever uses it as the
> first/primary IP.
>
> Is there an algorithm based on IP/program being used and the returned IP?
>



I can't sit and watch this thread anymore.  Something itchin' to say:

DNS, who can handle multiple A records in an optional round-robin
design, is perfectly fine to assign multiple A records to a resource.

/etc/hosts, which as always existed (back when the Internet was
created/new), was a unique record source only.  Having oddities in
/etc/hosts is expected IMHO when a "mistake" like multiple resources
assigned different records.


What's to stop you from creating slightly different records in
/etc/hosts?  Whats to stop you from hitting 'privserver' and
'pubserver', for private and public IPs respectively.


why are you so hung up on dual IPs for a single host?  would dnsmasq
provide a solution to dual A records for one resource?


I'll help, when I can.  but forcing this on /etc/hosts is a dead end.