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From: Aleksandr A Babaylov <.@babolo.ru>
To: Dave Seddon <dave@seddon.ca>
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Cc: Andrew Hannam <andrewh@itsallaboutbiz.com>,
	Robert Watson <rwatson@freebsd.org>, Julian Elischer <julian@elischer.org>,
	FreeBSD Net <net@freebsd.org>
Subject: Re: FreeBSD route tables limited 16?
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On Tue, Sep 14, 2010 at 04:31:39PM +1000, Dave Seddon wrote:
> It sounds like dedicating some space for this in the mbuf would be the
> best way forward, but the question is how much.  I'm worried that most
> freebsd users won't go for lots of route tables, which is why you went
> for 4 bits originally.
> 
> Within the network service provider space there is frequently a
> requirement for lots of virtual-routing with MPLS.  I imagine there are
> others in my situation, including vendors and people working on
> equipment like Cisco/Juniper/Lucatel.
> 
> Regarding the size to dedicate, the best number might be 12 bits or
> 4096.  This would allow a route table per VLAN on a 802.1q interface.
> (Actually I'm lying a little because the first and last vlan IDs aren't
> usable :) ).
> 
> Perhaps a separate option for non-common users who want many route
> tables would be best.  e.g.
> 
> GIANT_ROUTETABLES=12
Why not 16?
There can be several independent iface with VLAN on each.
arg1 in ipfw has 16 bits for fib number.

Yes, it is very special case when huge number of fib needed.