On 7 March 2017 at 23:27, Dennis Bohn <b...@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
