Filtering prefixes longer than /24

[itojun@iijlab.net]

>It appears some people are filtering prefixes longer than /24 in 6bone.
>We'd like to advertise /32.
>This was noticed when we wanted to change the peerings to a second router,
>and moved a "backup one" first and forced the traffic go through there; to
>certain locations, the return packets disappeared to the network
>advertising /24.
>The routing document says you MUST make arrangements with your peers if
>you do longer advertisements, but advertising these prefixes doesn't help
>any if they are being filtered by the third parties.

	because third parties are not in your arrangements.

>Filtering /48 and more specific is IMO ok to me, but /32 appears a little
>too strict.

	based on RFC2772 recommendation, i see the following filter in
	many places.  how do you measure "too strict"?

ipv6 prefix-list 6bone-filter seq 5 permit 3ffe::/17 le 24 ge 24
ipv6 prefix-list 6bone-filter seq 10 permit 3ffe:8000::/17 le 28 ge 28
ipv6 prefix-list 6bone-filter seq 12 deny 3ffe::/16
ipv6 prefix-list 6bone-filter seq 15 permit 2000::/3 le 16 ge 16
ipv6 prefix-list 6bone-filter seq 20 permit 2001::/16 le 35 ge 29

itojun