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network problem (fwd)

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  network problem (fwd) Pierre Frenkiel <pierre.frenkiel@gmail.com> - 2021-10-06 14:10 +0200
    Re: network problem (fwd) Greg Wooledge <greg@wooledge.org> - 2021-10-06 14:20 +0200
    Re: network problem (fwd) Brian <ad44@cityscape.co.uk> - 2021-10-06 17:20 +0200
      Re: network problem (fwd) Thomas Pircher <thp.debian@p5r.uk> - 2021-10-06 18:00 +0200
        Re: network problem (fwd) Brian <ad44@cityscape.co.uk> - 2021-10-06 18:30 +0200
      Re: network problem (fwd) rhkramer@gmail.com - 2021-10-07 02:00 +0200
        Re: network problem (fwd) David <bouncingcats@gmail.com> - 2021-10-07 02:10 +0200
          Re: network problem (fwd) Lee <ler762@gmail.com> - 2021-10-07 04:00 +0200
            Re: network problem (fwd) David <bouncingcats@gmail.com> - 2021-10-07 04:10 +0200
    Re: network problem (fwd) David <bouncingcats@gmail.com> - 2021-10-07 01:40 +0200
    Re: network problem (fwd) David Wright <deblis@lionunicorn.co.uk> - 2021-10-07 03:40 +0200

#240969 — network problem (fwd)

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please note that the main problem is
   "why the /etc/network/interfaces" is not used?"

best regards,
-- 
Pierre Frenkiel

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#240970

On Wed, Oct 06, 2021 at 02:09:23PM +0200, Pierre Frenkiel wrote:
> please note that the main problem is
>   "why the /etc/network/interfaces" is not used?"

Please show us the information you've been asked to show, by multiple
people:

ip addr
ip route

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#240978

On Wed 06 Oct 2021 at 14:09:23 +0200, Pierre Frenkiel wrote:

[...]

> I have the following problem on my laptop.
> my /etc/network/interfaces file contains:
>    auto enp0s1
>    iface enp0s1  inet static
>    address 192.168.1.10
>    netmask 255.255.255.0
>    gateway 192.168.1.1

Just in passing: The line with netmask 255.255.255.0 can be deleted.
It is a deprecated option, as is broadcast. See #912220.

-- 
Brian.

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#240979

Brian wrote:
>Just in passing: The line with netmask 255.255.255.0 can be deleted.
>It is a deprecated option, as is broadcast. See #912220.

Crikey, it is indeed deprecated. Just removing the line will probably
not be a good idea. I guess it can be deleted only when the address line
contains the netmask in CIDR notation:
>>    address 192.168.1.10/24

Thomas

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#240981

On Wed 06 Oct 2021 at 16:40:55 +0100, Thomas Pircher wrote:

> Brian wrote:
> > Just in passing: The line with netmask 255.255.255.0 can be deleted.
> > It is a deprecated option, as is broadcast. See #912220.
> 
> Crikey, it is indeed deprecated. Just removing the line will probably
> not be a good idea. I guess it can be deleted only when the address line
> contains the netmask in CIDR notation:
> > >    address 192.168.1.10/24

That looks to be the situation, according to examples in interfaces(5).
Mind you

  address 192.168.7.40

works for me. Don't ask me why. It is easy enough to rectify.

-- 
Brian.

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#240992

On Wednesday, October 06, 2021 11:15:11 AM Brian wrote:
> On Wed 06 Oct 2021 at 14:09:23 +0200, Pierre Frenkiel wrote:

> >    netmask 255.255.255.0
> >    gateway 192.168.1.1
> 
> Just in passing: The line with netmask 255.255.255.0 can be deleted.
> It is a deprecated option, as is broadcast. See #912220.

Does that mean 255.255.255.0 is the default netmask?

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#240993

On Thu, 7 Oct 2021 at 10:53, <rhkramer@gmail.com> wrote:
> On Wednesday, October 06, 2021 11:15:11 AM Brian wrote:
> > On Wed 06 Oct 2021 at 14:09:23 +0200, Pierre Frenkiel wrote:
>
> > >    netmask 255.255.255.0
> > >    gateway 192.168.1.1
> >
> > Just in passing: The line with netmask 255.255.255.0 can be deleted.
> > It is a deprecated option, as is broadcast. See #912220.
>
> Does that mean 255.255.255.0 is the default netmask?

The netmask has to be specified *somewhere*. My understanding
is that either CIDR or 'netmask' is required to do that. Read
about CIDR here:
https://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing#CIDR_notation

But others here are vastly more knowledgeable than I am about
networks, so additions or corrections are welcome, as always :)

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#240995

On 10/6/21, David  wrote:
> On Thu, 7 Oct 2021 at 10:53, <rhkramer@ > wrote:
>> On Wednesday, October 06, 2021 11:15:11 AM Brian wrote:
>> > On Wed 06 Oct 2021 at 14:09:23 +0200, Pierre Frenkiel wrote:
>>
>> > >    netmask 255.255.255.0
>> > >    gateway 192.168.1.1
>> >
>> > Just in passing: The line with netmask 255.255.255.0 can be deleted.
>> > It is a deprecated option, as is broadcast. See #912220.
>>
>> Does that mean 255.255.255.0 is the default netmask?
>
> The netmask has to be specified *somewhere*. My understanding
> is that either CIDR or 'netmask' is required to do that. Read
> about CIDR here:
> https://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing#CIDR_notation
>
> But others here are vastly more knowledgeable than I am about
> networks, so additions or corrections are welcome, as always :)

It's Classless Inter-domain Routing (CIDR) now and network masks are
no longer supported [1].  If you take a look at RFC-950 [2], there is
no requirement that the network and sub-network bits of an address be
contiguous.  252.252.252.252 was a perfectly valid mask and yields the
same number of host bits (8) as a 255.255.255.0 mask does.

Then along came CIDR and dis-contiguous network/subnet bits were prohibited.

Lee


[1]  Specifically, _bitmasks_ are no longer supported. "network masks"
are now just another way of specifying the first however many bits of
an address that make up the network portion of an address - eg. /24
and 255.255.255.0 both specify the first 24 bits of an address

[2]  https://datatracker.ietf.org/doc/html/rfc950#page-15

   3.  A Class C Network Case (illustrating non-contiguous subnet bits)

      For this case, assume that the requesting host is on class C
      network 192.1.127.0, has address 192.1.127.19, that there is a
      gateway at 192.1.127.50, and that on network an 3-bit subnet field
      is in use (01011000), that is, the address mask is 255.255.255.88.

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#240996

On Thu, 7 Oct 2021 at 12:53, Lee <ler762@gmail.com> wrote:
> On 10/6/21, David  wrote:

> > But others here are vastly more knowledgeable than I am about
> > networks, so additions or corrections are welcome, as always :)

> It's Classless Inter-domain Routing (CIDR) now and network masks are
> no longer supported [1].  If you take a look at RFC-950 [2], there is
> no requirement that the network and sub-network bits of an address be
> contiguous.  252.252.252.252 was a perfectly valid mask and yields the
> same number of host bits (8) as a 255.255.255.0 mask does.
>
> Then along came CIDR and dis-contiguous network/subnet bits were prohibited.

Ahhh, that's interesting, I didn't know about that aspect.

Thank you for taking the time to explain clearly, with links.
I really appreciate it!

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#240991

On Wed, 6 Oct 2021 at 23:09, Pierre Frenkiel <pierre.frenkiel@gmail.com> wrote:
>
> please note that the main problem is
>    "why the /etc/network/interfaces" is not used?"

Ok. Noted.

Several knowledgeable and helpful people have already
made an effort trying to help you answer exactly this.
You can find those efforts in the 4 links labelled "Follow-Ups"
at the bottom of this web page:
https://lists.debian.org/debian-user/2021/10/msg00244.html

If you do not engage with those efforts then it really is a
puzzle to understand what kind of help you expect when
you write to this list.

Should we conclude that you prefer to solve this without
our assistance?

If that is the case, you could do the following:

First, learn what DHCP is.

Second, learn what all the commands (that others
have suggested in the links above) do, and how to
understand their outputs.

Third, use those commands to answer the question yourself.

If that is not the case, then perhaps you could explain
what kind of help you do expect when you ask a question
here.

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#240994

On Wed 06 Oct 2021 at 14:09:23 (+0200), Pierre Frenkiel wrote:
> please note that the main problem is
>   "why the /etc/network/interfaces" is not used?"

> I have the following problem on my laptop.
> my /etc/network/interfaces file contains:
>    auto enp0s1
>    iface enp0s1  inet static
>    address 192.168.1.10
>    netmask 255.255.255.0
>    gateway 192.168.1.1
> 
>    but after boot, ifconfig gives
> 
>    address 192.168.0.163
>    netmask 255.255.255.0
>    gateway 192.168.1.1
> 
>    Then, networking works i.e. I can reach Internet, but of course
>    not my desktop and other devices 192.168.1.xx
> 
>    I looked on the entire disk to find where this address 192.168.0.163
>    is hidden, but I was unable to find it !
> 
>    rather strange, isn't it?

One possibility might be that you've somehow got yourself connected to
the WAN side of your router, rather that the LAN side.
I think you should login to your router and see what the address of
the Internet Port is.
I seem to remember that happening to someone here with one of those
"captive" or ISP-managed modem/routers.
It's one reason why we run three routers at home: one that Cox rent,
the real one (mine), and one with a broken WAN port that we use as
a switch and wireless repeater.

Cheers,
David.

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