On Oct 11, 2011, at 12:05 AM, Jari Arkko wrote:

> That being said, if the home routers have to discover their IPv6 prefix 
> through a protocol and store it in flash, they could probably do so also for 
> a router ID. Unless there was some chicken and egg problem that required the 
> router ID for all this discovery to work...

(z)ospf requires the router to have a router id in order to join the network, 
which it has to do before it can receive the LSAs from other routers in the 
area to inspect their subnet prefixes. So making the router id dependent on the 
prefix doesn't make a lot of sense to me.

While a MAC Address is not guaranteed to be globally unique, it is intended to 
be; places where duplicates have been seen tend to be manufacturing errors. 
From that perspective, grabbing the least significant 32 bits from a MAC 
address as a first guess seems reasonable. What one would then need to do is 

1) receive the LS Database
2) inspect for other instances of the same router id
3a) if found, attempt to flush the LSA (it might be an old LSA from the same 
router)
3b) if flushed and it is then re-advertised back, there is a collision and the 
other router is asserting ownership; pick a random number

One obviously doesn't actually announce any LSAs using the router ID until a 
unique router id is established.
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