On Tue, Aug 25, 2020 at 07:27:33AM -0400, K. Scott Helms wrote: > I think a fairly easy thing to do is see what other large retail ISPs > have done. Comcast, as an example, lists all of the ports they block > and 0 is blocked. I do recommend that port 0 be blocked by all of the > ISPs I work with and frankly Comcast's list is a pretty good one to > use in general, though you will get some pushback on things like SMTP. > > https://www.xfinity.com/support/articles/list-of-blocked-ports
I may be reading the table incorrectly, but it seems to me Comcast is *not* blocking UDP port 0 according to the above URL? > Transit providers are a little bit different, but then again port 0 is > also different since AFAIK it's never had a legitimate use case. It's > always been a reserved port. I'd personally block it if I ran a > transit, but I'd be more willing to open it up for one of my large > customers (in a limited way) than I would on the retail side. > > https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml What about UDP IP fragmentation? Kind regards, Job
