Re: [gentoo-user] Re: Link-local ipv6 address in /etc/hosts? in browsers?

[Michael Mol]

On Thu, Jan 19, 2012 at 4:55 PM, Grant Edwards
<grant.b.edwards@×××××.com> wrote:
> On 2012-01-19, Michael Mol <mikemol@×××××.com> wrote:
>
>> Indeed. Other reasons to avoid using LL addresses unless necessary:
>> What if the MAC address on the server changes?
>
> It won't.  It's an embedded device with a hard-wired MAC that the user
> can't change.

It was more a philosophical question, not one of the specific use
case. In most systems, hardware NICs fail and may be replaced. (Well,
virtualization is making that a bit odd, but still.) I have ideas
about your use case, but I can't and won't judge because I don't know
enough specifics. Your product, not mine. :)

>
>> What if your network grows to have hundreds of clients?
>
> Then people probably won't be using L-L addresses.  However, for a
> network that consists of 6 small devices all living inside a cabinet
> with no router, DHCP server, or connection to the outside workd, L-L
> is great.

Sure, so long as various applications get fixed to understand LL
addresses and are corrected to direct traffic to the appropriate
interfaces, which is something I'd definitely like to see.

>> Do you really want that much broadcast and wide multicast (think
>> DNS-SD and NTP in multicast mode) traffic on the same Ethernet
>> segment?
>
> That bit I don't understand.  It's no worse that ARP, and we seem to
> live with that quite easily.

Not just arp, but actual broadcast/multicast data. If you've ever run
PulseAudio and enabled network sources and sinks on a couple boxes,
you might have accidentally discovered an easy way to bring a wireless
network to its knees. And that's just something I've had personal
experience with. Come to think of it, that's a good reason I should
continue to keep my home wired and wireless networks on separate
subnets, and not simply bridged as I'd done at the time.

One anecdote a friend of mine gave me...there was a network he was
brought in to manage where he discovered that a huge campus of over a
thousand hosts was configured as one large ethernet segment with
various-speed links bridging smaller islands. The slower links were
absolutely flooded with arp and netbios broadcasts, and the network
moved along at a crawl. Chopping that up into a few routed subnets
gave the entire network a massive performance boost.

>
>> LL addresses are very useful for diagnostic and investigation
>> purposes, of course.
>
> Indeed, and that's what I'm doing.

-- 
:wq