Time to add 2002::/16 to bogon filters?

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1

Hi Youssef,

My original reply wasn't sent to the Nanog list.

Team Cymru considers 2002::/16 and 192.88.99.0/24 to be legitimate
prefixes at this time, and will be not be adding them to our bogon
filters. Our interpretation of the 6to4 anycast rfc is that while these
are encouraged to be made obsolete, in practice they may still be in
use, excluding them from being universally defined as a bogon in our feed.

The RFC in question:
https://tools.ietf.org/html/rfc7526

The rule, as it always should be, is to know your network, and know what
is best for it. As noted in the RFC you are encouraged to review any
current deployments and any existing filtering and adjust based on your
own discretion.

Regards,

Gary McArtor
Team Cymru

2

Hi Youssef,

My original reply wasn't sent to the Nanog list.

Team Cymru considers 2002::/16 and 192.88.99.0/24 to be legitimate
prefixes at this time, and will be not be adding them to our bogon
filters. Our interpretation of the 6to4 anycast rfc is that while these
are encouraged to be made obsolete, in practice they may still be in
use, excluding them from being universally defined as a bogon in our feed.

The RFC in question:
RFC 7526 - Deprecating the Anycast Prefix for 6to4 Relay Routers

The rule, as it always should be, is to know your network, and know what
is best for it. As noted in the RFC you are encouraged to review any
current deployments and any existing filtering and adjust based on your
own discretion.

Regards,

Gary McArtor
Team Cymru

On 6/28/18 2:32 PM, Rabbi Rob Thomas wrote: FYI, the question has been raised. I'm not sure if this is wise or not.
Gary, what are your thoughts?

Subject: Re: Time to add 2002::/16 to bogon filters?
Date: Thu, 28 Jun 2018 21:11:22 +0200
From: Youssef Bengelloun-Zahr <bengelly@gmail.com>
To: Job Snijders <job@ntt.net>
CC: NANOG [nanog@nanog.org] <nanog@nanog.org>

Hello Job,

Thank you for this feedback. I guess that NTT adopting this as a best
practice will ring some bells around.

Do you know if Team Cymru has updated their filters accordingly ?

Best regards.

Dear alll,

Thank you all for your input. Just a heads-up - we deployed a few days ago.

NTT / AS 2914 now considers "2002::/16 le 128" and "192.88.99.0/24 le 32"
to be bogon prefixes, and no longer accepts announcements for these
destinations from any EBGP neighbor.

Kind regards,

Job

I think it's still used a bit ? I see today announcements over the following OriginAS over more than 2000 peers.

as1103 SURFnet bv
as1835 Forskningsnettet - Danish network for Research and Education
as2847 Kauno technologijos universitetas
as6939 HURRICANE
as16150 Availo Networks AB
as25192 CZ.NIC, z.s.p.o.
as28908 A3 Sverige AB

I'm pretty curious about customers impacts if your drop these anycast 6to4 prefixes from your RIB/FIB :wink:

At home, I use HE.net tunnel broker, because no native IPv6 (yes we already lose matches against Belgium regarding IPv6 and ... beer) and a quick dump shows traffic to 2002:/16 :

sudo tcpdump -ni any 'net 2002::/16'

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on any, link-type LINUX_SLL (Linux cooked), capture size 262144 bytes
15:10:59.588097 IP6 2002:6bab:c6c6:0:e561:b9f7:b221:a73.51413 > 2001:470:1f12:dead::beef.51413: UDP, length 94
15:10:59.588233 IP6 2001:470:1f12:dead::beef.51413 > 2002:6bab:c6c6:0:e561:b9f7:b221:a73.51413: UDP, length 365

So I'm pretty sure it's still used when no IPv6 is available from an eyeball provider to mount a 6to4 tunnel over a provider that have well deployed IPV6 infrastructure. Perhaps some of the 6to4 tunnel can be tuned to not use anycast prefixes ?

3

I think it's still used a bit ? I see today announcements over the
following OriginAS over more than 2000 peers.

as1103 SURFnet bv
as1835 Forskningsnettet - Danish network for Research and Education
as2847 Kauno technologijos universitetas
as6939 HURRICANE
as16150 Availo Networks AB
as25192 CZ.NIC, z.s.p.o.
as28908 A3 Sverige AB

Announced and used are two different things.. :slight_smile:

> sudo tcpdump -ni any 'net 2002::/16'
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on any, link-type LINUX_SLL (Linux cooked), capture size 262144 bytes
15:10:59.588097 IP6 2002:6bab:c6c6:0:e561:b9f7:b221:a73.51413 > 2001:470:1f12:dead::beef.51413: UDP, length 94
15:10:59.588233 IP6 2001:470:1f12:dead::beef.51413 > 2002:6bab:c6c6:0:e561:b9f7:b221:a73.51413: UDP, length 365

I'm pretty sure that 2002: address is (a) *your* end of the tunnel and (b)
only visible inside your network and *inside* the HE tunnel to the other end.
In other words, it shouldn't be seen out on the public net if it's transiting
an HE tunnel. I bet if you changed that '-i any' to '-i wlan' (for whatever
your router calls the outbound-facing interface) you won't see traffic on 2002:

4

I'm pretty sure that 2002: address is (a) *your* end of the tunnel and (b)
only visible inside your network and *inside* the HE tunnel to the other end.
In other words, it shouldn't be seen out on the public net if it's transiting
an HE tunnel. I bet if you changed that '-i any' to '-i wlan' (for whatever
your router calls the outbound-facing interface) you won't see traffic on 2002:

You're right, it does need to be public to work :wink: So my question is why it is still and it was announced on DFZ ?

Regards,

5

2002::/16 is still valid - not a bogon as long as there is an IPv4 Internet. Add the IPv4 bogons, though (2002:7f00:0000::/48 through 2002:7f.ff:ff.ff::/48, & others)