WEBINAR TUESDAY: Can We Make IPv4 Great Again?

Baldur Norddahl baldur.norddahl at gmail.com
Wed Mar 8 10:27:52 UTC 2017

On 08-03-2017 00:27, Dennis Bohn 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?
> dennis

Many features of IPv6 depends on link local. Take a look at the routing 
table of your computer - you will find that most routes have a next hop 
with a link local address. Many buildin protocols, such as RA and 
DHCPv6, use link local to communicate without depending on any 

Many protocols with automatic discovery will use link local - why would 
you want your printer or local NAS server to use a public IP when link 
local works? In fact, you may prefer the printer to be only on link 
local so it can not be accessed from outside. The public IP is something 
your ISP assigns to you, so using that unnecessary only makes your setup 
vulnerable to problems if the internet is down. You could assign an ULA 
prefix https://en.wikipedia.org/wiki/Unique_local_address for your 
network but most people wont.



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