[187770] in North American Network Operators' Group
Re: Thank you, Comcast.
daemon@ATHENA.MIT.EDU (Mikael Abrahamsson)
Fri Feb 26 01:20:34 2016
X-Original-To: nanog@nanog.org
Date: Fri, 26 Feb 2016 07:20:28 +0100 (CET)
From: Mikael Abrahamsson <swmike@swm.pp.se>
To: Jared Mauch <jared@puck.nether.net>
In-Reply-To: <DDB4053B-6E54-467A-AB1B-35DAC8B55D8D@puck.nether.net>
Cc: NANOG list <nanog@nanog.org>
Errors-To: nanog-bounces@nanog.org
On Thu, 25 Feb 2016, Jared Mauch wrote:
> Make sure you permit TCP/53 for DNS queries so if TC=1 lookups work.
Speaking of which, historically ISPs have been blocking TCP/135, TCP/445
and a few others towards customers (at least that's what I know). TCP/25
seems to be blocked as well.
Why isn't UDP/53 blocked towards customers? I know historically there were
resolvers that used UDP/53 as source port for queries, but is this the
case nowadays?
I know providers that have blocked UDP/53 towards customers as a
countermeasure to the amplification attacks. As far as I heard, there were
no customer complaints.
--
Mikael Abrahamsson email: swmike@swm.pp.se
