WEBINAR TUESDAY: Can We Make IPv4 Great Again?

Mike Jones mike at mikejones.in
Wed Mar 8 00:15:20 UTC 2017

On 7 March 2017 at 23:27, Dennis Bohn <bohn at adelphi.edu> wrote:

> >
> >
> > In addition, IPv6 has link local addresses.
> > This one seemingly insignificant detail causes so much code churn
> > and is probably responsible for 10 years of the IPv6 drag.
> AFAICT, Cisco V6 HSRP (mentioning that brand only because it caused me to
> try to figure something out, a coincidence that this is in reply to Jakob
> from Cisco but is based on what he wrote)  relies on Link Local addresses.
> I didn't understand why link locals should be there in the first place
> seemed klugey and have googled, looked at rfcs and tried to understand why
> link local addresses were baked into V6. The only thing I found was that it
> enabled interfaces on point to point links to be unaddressed in V6. (To
> save address space!??) Can anyone point me in a direction to understand the
> reasoning for link local addressing?

So you can print whilst your Internet connection is down. IPv6 allowed
people to rethink IPv4 assumptions, and they realised that a lot of IPv4
things were hacks to work around a lack of functionality in the protocol.
NAT has polluted peoples minds when it comes to the distinctions between
local and global addressing.

Why would you use a global address, with an extra code check to make sure
it is on a directly attached interface, to point a route at? "Router 2 on
interface B" makes more sense to me than "Router with global address 12345"
in this context.

I would also have loved it if the all-routers-anycast thing had been better
defined rather than deprecated. One of the potential default behaviours
could have been fe80:: as a default gateway on every segment, with a
logical meaning of "All upstream routers on this interface".

- Mike

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