This RIPE Security PDF is also a good starting point: https://www.ripe.net/media/documents/IPv6Security-Slides.pdf

It advises blocking ICMP Type 137 (Redirect) and Type 138 (Route Renumbering). The other types should not be blocked; however, some prefer to rate limit Echo requests/replies (Type 128 and 129). You may want to rate limit these types of requests to your infrastructure nodes or handle them in the control plane on your nodes.

Additionally, at the ISP level, you could implement some ingress ACLs such as:

Block everything to documentation address space (RFC3849):
deny ipv6 any 2001:db8::/32 icmp-off
Block everything to benchmarking address space (RFC5180):
deny ipv6 any 2001:2::/48 icmp-off
Block everything to Automatic Multicast Tunneling (RFC7450):
deny ipv6 any 2001:3::/32 icmp-off
Block everything to deprecated ORCHID/ORCHIDv2 (RFC4843/RFC7343):
deny ipv6 any 2001:10::/28 icmp-off
deny ipv6 any 2001:20::/28 icmp-off
Block Router Advertisements (RAs):
deny icmpv6 any any router-advertisement icmp-off
Allow everything else from locally connected internet customers to the IPv6 global unicast space (as a rudimentary/coarse anti-source-IP spoofing measure):
permit ipv6 <YOUR IPv6 space> 2000::/3

I think there are some more you could block, but always be sure you know what's in your filters and change them according to your network requirements.

In addition, it's recommended to implement anti-spoofing protection at the ISP level. Only allow traffic from your customers originating from the IP space they were assigned via DHCPv6 or PPPoE.

Rinse

On 6-10-2024 11:28, Michiel Klaver via ipv6-wg wrote:

http://shouldiblockicmp.com/


-----Original message-----
Am 05.10.2024 um 21:11:22 Uhr schrieb Sheikh Md Seum via ipv6-wg:

While going through the deployment procedure I was not able to find
any BCP/BCOP regarding how to filter ICMPv6, what standards should be
followed.

Don't filter it at all at the ISP level for your customers.

The neighbor discovery packets can't be abused from other links because
they will be discarded when they don't have TTL of 255.
Make sure you reject RAs from the customers on your PPP links.

Although, inside a link (e.g. on a office network), filtering for
certain packages like RA is needed to avoid certain intended or
accidental stuff.

Other stuff like the destination unreachable must not be blocked at all.

ICMPv6 isn't a security risk itself.