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Re: introducing a limit for the number of prefixes/routes from RA (IPv6)


Thus wrote Dennis Ferguson (

> On 11 May 2011, at 16:19 , S.P.Zeidler wrote:
> > at present, there is no limit to the number of prefixes (and thus, routes)
> > that a IPv6 autohost will accept via router advertisements.

> I think instead that the problem is with IPv6-specific code like this:
> struct nd_prefix *                    
> nd6_prefix_lookup(struct nd_prefixctl *key)
> {                                     
> }  
> A linear list like that is appropriate when there is normally just
> one or two of something but where, only in some extreme corner case,
> there might be a dozen or two manually configured, like IPv4 interface
> addresses on a single interface.

Right. I'm not expecting more than one or two prefixes being legally on one
LAN at the same time, take two interfaces, maybe three. I picked 42 as
"larger than most people will ever need to change".

> What this is doing, however, is a
> full-blown automatic routing protocol, and the only reason to expect
> there should only be a few of those is if you don't expect anyone
> to actually use IPv6 for anything serious.

It's SLAAC, the IPv6 moral equivalent of the "give me an IP address and a
default router" DHCP in IPv4. It's not supposed to be an IGP.

-- (S.P.Zeidler)

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