[GLLUG] Adding multiple addresses to multiple interfaces

Chris Bell chrisbell at chrisbell.org.uk
Tue Jan 2 21:04:41 UTC 2018

On Tuesday, 2 January 2018 20:21:54 GMT Andy Smith via GLLUG wrote:
> Hello,
> On Tue, Jan 02, 2018 at 06:08:34PM +0000, Chris Bell wrote:
> > Correct. I calculated the 6to4 address before trying to configure the
> > TP-Link modem, and the modem immediately confirmed that it was correct.
> Hmm, 6to4 sounds like something guaranteed to give you grief.
> Honestly I wouldn't bother with IPv6 without native IPv6.
I prefer to iron out the bugs before the direct IPv6 is switched on without 
warning. I tried to set up a Hurricane Electric tunnel, but failed to get any 
reply from them. 
> What's with all the site local v6 addresses? What happens if you
> stick only to global scope addresses?
IPv6 is supposed to enable this, the addresses chosen are within the correct 
range, and created as specified using the suggested random generator.
> Why is there an "up" on the end of each iface line? I haven't seen
> that syntax before and can't seem to find it mentioned in
> https://manpages.debian.org/stretch/ifupdown/interfaces.5.en.html
> but perhaps it is supported.
I think it used to be a requirement, perhaps no longer needed, but I have 
tried many ways to get it to work.
> It would be best not to use "ifconfig" for diagnostic purposes
> because some of the configurations that can be set by ifupdown
> cannot be reported correctly by "ifconfig". Most of the time with
> simple configurations you get lucky and it tells you everything, but
> things started diverging over a decade ago and it's getting worse.
> Mostly you need to use "ip" for whatever you are used to using
> "ifconfig" for.
It is just a quick and easy way to run a check.
> This may help:
>     http://baturin.org/docs/iproute2/
It could be shorewall6 blocking the interfaces, but then I could not explain 
why the last interface (only) appears to work.
> Cheers,
> Andy
I have just confirmed that I can add the data using IP, but it did not survive 
a reboot.
Whichever way I do it, it must survive a re-boot. Cadent are about to dig up 
and replace the gas supplies to around 200 local houses over about three 
months, and that is very likely to break the old paper and shellac insulated 
mains feeder on multiple occasions. There have already been many shorts with 
water getting into joints and cables causing supply failures, including shorts 
between phases a couple of weeks ago, so I can not rely on the local mains. I 
do not have a standby generator, and a UPS only lasts for a short while.
I share the same supply feeder with the street lighting and the main A40 
Western Avenue Gypsy Corner traffic lights, and there is chaos when it fails.

Chris Bell
Website http://chrisbell.org.uk

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