Re: No ifconfig
On Monday 21 August 2017 12:11:38 Christian Seiler wrote:
> On 08/21/2017 05:03 PM, Gene Heskett wrote:
> > On Monday 21 August 2017 09:08:11 Christian Seiler wrote:
> >> 2. Can't add multiple IP addresses to the same interface and
> >> (worse) even if multiple IP addresses are assigned to the
> >> same interfaces it only shows the primary address
> >
> > I don't know as to how ifconfig sets it up, but its a piece of cake
> > to edit /etc/network/interfaces to do that. If I bring in a new
> > router, I uncomment this stanza in the interfaces file:
> > ================
> > #auto eth0:1
> >
> > # to access reset to 192.168.0.1 routers/switches on the 2nd cat5
> > port #iface eth0:1 inet static
> > #address 192.168.0.3
> > #netmask 255.255.255.0
> > ==============
> > giving me an address I can use to talk to and configure the new
> > router.
>
> Yeah, that's the old way of doing this via an alias interface. I was
> talking about the new-style way of doing so though.
>
> For example:
>
> auto eth0
>
> iface eth0 inet static
> address 192.168.0.1/24
> address 192.168.0.42/24
> address 10.5.6.7/8
>
> This will work, and it will assign all IPs to the interface (the first
> one being the primary and the source IP of outgoing packets where the
> program doesn't explicitly bind anything). And "ip a" will show all
> three addresses, but "ifconfig -a" will only show the first.
>
Ok, but then how do you differentiate between the addresses without
the :1 [:2 etc] notation?
It doesn't seem right that is would bang all the assigned addresses with
duplicate data.
> Alias interfaes are kind of legacy, and while they still work, they do
> have a couple of drawbacks: they aren't really an own interface
> because they share options with the interface they are based on (which
> can be confusing if you want to change interface options), there is no
> way to automatically add a new IP to a given interface without probing
> first which aliases have already been "used up", the alias namespace
> is limited by both the max length of an interface name and the
> limitation of the alias part itself.
I haven't seen, or needed, one of the newer critters yet. But I'll be
interested in the details when it does jump the fence into my domain.
> But don't get me wrong: if it works for you with alias interfaces, I'm
> certainly not going to tell you to change that - because those also do
> work with the "ip" utility. The major issue I "ifconfig" has here is
> that it doesn't see the additional IP addresses of interfaces added by
> other tools - so that when you rely on ifconfig you _don't_ see the
> actual entire network configuration of the system, but only a part of
> it. So it's actually counter-productive when you're troubleshooting a
> system.
>
> >> (2) is really bad, especially the part where it does not show
> >> all of the IPs that were assigned by other tools, for example
> >
> > Huh? ifconfig doesn't even need a -a option to show me eth0:1 if ts
> > configured and up.
>
> Yes, for alias interfaces it does. For the additional IPs added to the
> interface itself it doesn't.
>
> >> NetworkManager, or Debian's own ifupdown via
> >> /etc/network/interfaces.
> >
> > Please don't equate those two.
>
> I was talking about how these configure multiple IPs when you use
> them. Both use the newer kernel interface that allows you to specify
> multiple IPs on the same interface, while ifconfig uses the old
> interface that assumes a single IP per interface. And I just used
> the most prominent programs in Debian as examples for this, but all
> other management tools I know of (conman, systemd-networkd, ...)
> also use the newer interface.
>
> I really didn't want to discuss the merits or problems of each
> individual software package.
>
> Regards,
Thank you, Christian
Cheers, Gene Heskett
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>
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