Multiple IP Addresses For Same Host in /etc/hosts

Tennis Smith

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Dec 9, 2003, 5:05:54 PM12/9/03

to

Hi,

Can you have more than one address associated with a single host name
in the /etc/hosts file? Will it cause any problems?

For example, if lets say that hostA has multiple interfaces, and
therefore
multiple addresses:

1.1.1.1 hostA
2.2.2.2 hostB
3.3.3.3 hostA
4.4.4.4 hostC

Will that cause a problem?

TIA,
-Tennis

Bit Twister

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Dec 9, 2003, 5:15:39 PM12/9/03

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I would assume if I do anything using hostA, ssh, rlogin, ping,
ftp,...., host lookup will fetch 1.1.1.1.

murph

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Dec 10, 2003, 3:32:19 AM12/10/03

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Bit Twister <BitTw...@localhost.localdomain> wrote in message news:<slrnbtcicb.s...@wb.home>...

I'm not sure but i think yes
It is possible to have more than one IP on one interface (you create
virtual interface) and there should be no problem also with more
interfaces

Ian Fitchet

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Dec 10, 2003, 5:01:39 AM12/10/03

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tennis...@yahoo.com (Tennis Smith) writes:

> Can you have more than one address associated with a single host name
> in the /etc/hosts file? Will it cause any problems?

On Solaris you must put the IPs for any individual host on adjacent
lines in hosts. Your original hosts would only let a resolver
discover 1.1.1.1 for hostA, whereas:

1.1.1.1 hostA
3.3.3.3 hostA
2.2.2.2 hostB
4.4.4.4 hostC

would mean a resolver will find 1.1.1.1, 3.3.3.3 for hostA. It's a
subtle difference and can make/break your applications.

The man page says:

The hosts file has one entry for each IP address of each host. If
a host has more than one IP address, it will have one entry for
each, on consecutive lines.

Cheers,

Ian

Doug Freyburger

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Dec 10, 2003, 2:03:49 PM12/10/03

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Tennis Smith wrote:
>
> Can you have more than one address associated with a single host name
> in the /etc/hosts file? Will it cause any problems?

Sure, no problem.

> For example, if lets say that hostA has multiple interfaces, and
> therefore multiple addresses:
>
> 1.1.1.1 hostA
> 2.2.2.2 hostB
> 3.3.3.3 hostA
> 4.4.4.4 hostC

No, that's four different hosts. You're aware that a string comparison
of "hostA" and "hostB" will come out different, right? Also forget case:

1.1.1.1 hosta host
2.2.2.2 hostb host
...

Moshe Ivgy

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Apr 16, 2014, 5:07:17 AM4/16/14

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which manual page says that?
The Unix man page for hosts does NOT say that..
http://unixhelp.ed.ac.uk/CGI/man-cgi?hosts

Barry Margolin

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Apr 16, 2014, 11:20:38 AM4/16/14

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In article <7de1b3e1-5d09-4d1b...@googlegroups.com>,

He said "Solaris" on the first line of the reply.

> The Unix man page for hosts does NOT say that..
> http://unixhelp.ed.ac.uk/CGI/man-cgi?hosts

That man page is for Linux. It's also about a dozen years old. Although
not as old as the one on my Snow Leopard system, which claims to be from
1993! But I don't believe it, because it mentions both IPv6 and Mac OS
X, neither of which existed 20 years ago.

--
Barry Margolin, bar...@alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***

Casper H.S. Dik

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Apr 16, 2014, 12:25:21 PM4/16/14

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Barry Margolin <bar...@alum.mit.edu> writes:

>> On Wednesday, December 10, 2003 12:01:44 PM UTC+2, Ian Fitchet wrote:

>> > The man page says:
>> >
>> > The hosts file has one entry for each IP address of each host. If
>> > a host has more than one IP address, it will have one entry for
>> > each, on consecutive lines.
>> >
>> >
>> > Cheers,
>> >
>> > Ian

...

>>
>He said "Solaris" on the first line of the reply.

I don't think this is enforced.

What actually happens is that we read the /etc/hosts file in
nscd and hash it; when we lookup the hostname we will return
all the entries that are found in that hashbucket and match
the hostname.

Casper