nanog mailing list archives
Re: TCP and UDP Port 0 - Should an ISP or ITP Block it?
From: "K. Scott Helms" <kscott.helms () gmail com>
Date: Tue, 25 Aug 2020 07:27:33 -0400
Douglas, 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 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 Scott Helms On Tue, Aug 25, 2020 at 7:16 AM Douglas Fischer <fischerdouglas () gmail com> wrote:
I think that the subject of the e-mail is very self-explanatory. With some analysis of what is running over our network, ISP or ITP, we will be able to see some TCP/UDP(mostly UDP) packets with source or destination to port 0. I can think of a genuine use of it. (Maybe someone cloud help me see what I'm not seen.) So I have two questions: a) Should an ISP block that Kind of traffic? (like anti-spoofing on BNG/B-RAS) b) Should a Transit Provider block that Kind of traffic? -- Douglas Fernando Fischer Engº de Controle e Automação
Current thread:
- TCP and UDP Port 0 - Should an ISP or ITP Block it? Douglas Fischer (Aug 25)
- Re: TCP and UDP Port 0 - Should an ISP or ITP Block it? K. Scott Helms (Aug 25)
- Re: TCP and UDP Port 0 - Should an ISP or ITP Block it? Job Snijders (Aug 25)
- Re: TCP and UDP Port 0 - Should an ISP or ITP Block it? K. Scott Helms (Aug 25)
- Re: TCP and UDP Port 0 - Should an ISP or ITP Block it? Mike Hammett (Aug 25)
- Re: TCP and UDP Port 0 - Should an ISP or ITP Block it? Pim van Stam (Aug 25)
- Re: TCP and UDP Port 0 - Should an ISP or ITP Block it? Töma Gavrichenkov (Aug 25)
- Re: TCP and UDP Port 0 - Should an ISP or ITP Block it? Job Snijders (Aug 25)
- Re: TCP and UDP Port 0 - Should an ISP or ITP Block it? K. Scott Helms (Aug 25)
- Re: TCP and UDP Port 0 - Should an ISP or ITP Block it? Job Snijders (Aug 25)
- Message not available
- Re: TCP and UDP Port 0 - Should an ISP or ITP Block it? John Kristoff (Aug 25)
- Re: TCP and UDP Port 0 - Should an ISP or ITP Block it? Tom Beecher (Aug 25)
- Re: TCP and UDP Port 0 - Should an ISP or ITP Block it? K. Scott Helms (Aug 25)
- Message not available
- Re: TCP and UDP Port 0 - Should an ISP or ITP Block it? K. Scott Helms (Aug 26)