The goal isn’t to filter _all_ ICMP. The goal is to permit ICMP that is needed for correct operation across the global network while protecting from externally spoofed packets. For example, on the IPv4 side, there arguably is no value to timestamp requests and address mask requests externally, so dump them. Thoughts? EKG
On May 14, 2017, at 9:42 AM, Alarig Le Lay <alarig@swordarmor.fr> wrote:
On dim. 14 mai 09:29:45 2017, Eric Germann wrote:
Good morning all,
I’m looking for some guidance on best practices to secure IPv6 on Linux end nodes parked in AWS.
Boxes will be running various services (DNS for starters) and I’m looking to secure mainly ICMP at this point. Service filtering is fairly cut and dried.
I’ve reviewed some of the stuff out there, but apparently I’m catching too many of the ICMP types in the rejection as routing eventually breaks. My guess is router discovery gets broken by too tight of filters.
Thanks for any guidance.
EKG
Hi,
Filtering ICMP breaks Internet and it is even more true with IPv6 as almost all the bootstrap is based on ICMP (ND, RD, RA, etc.). Plus, you will break connections where there is a MTU change on the path.
So, my advise is simply to not filter ICMP and ICMPv6. And by the way, why do want to filter ICMP? You will not be DDoSed with pings.
-- alarig