[192387] in North American Network Operators' Group
Re: Large BGP Communities beacon in the wild
daemon@ATHENA.MIT.EDU (Owen DeLong)
Thu Oct 27 11:47:20 2016
X-Original-To: nanog@nanog.org
From: Owen DeLong <owen@delong.com>
In-Reply-To: <20161027061946.GF37101@Vurt.local>
Date: Thu, 27 Oct 2016 08:47:08 -0700
To: Job Snijders <job@ntt.net>
Cc: Jared Mauch <jmauch@us.ntt.net>, nanog@nanog.org, routing-wg@ripe.net
Errors-To: nanog-bounces@nanog.org
I don=E2=80=99t mind the move to 32, but I hope the vendors are getting =
appropriately smacked for squatting and that those attributes are not =
allowed to be misappropriated by the vendors.
We have a standards process for a reason and vendors simply squatting on =
numbers is a violation of that process which cannot be allowed to stand =
unless we wish to establish that as precedent and simply allow vendors =
to claim numbers as they wish.
This already happened with the BSD community in their implementation of =
a pseudo-VRRP like capability and now two different vendors have abused =
BGP path attributes.
This is not a good path for us to continue.
Owen
> On Oct 26, 2016, at 11:19 PM, Job Snijders <job@ntt.net> wrote:
>=20
> Dear Internet,
>=20
> Through this beacon it was discovered that a vendor was squatting on =
BGP
> Path Attribute value 30. And another vendor sat on 31.
>=20
> So, a twisted turn of events, the Large BGP Communities effort has =
ended up
> with BGP Path Attribute value 32 - very befitting if you look at the =
very
> problem we're trying to solve :-)
>=20
> The beacon has been updated to use the new IANA assigned value, =
nothing
> else was changed. Hopefully we are in the clear this time around!
>=20
> Please verify if you can see 192.147.168.0/24 and 2001:67c:208c::/48
>=20
> Kind regards,
>=20
> Job
>=20
> On Tue, Oct 11, 2016 at 05:01:56PM +0200, Job Snijders wrote:
>> Large BGP Communities are a novel way to signal information between
>> networks. An example of a Large BGP Communities is: =
2914:4056024901:80.
>>=20
>> Large BGP Communities are composed of three 4-octet integers, =
separated
>> by something like a colon. This is easy to remember and accommodates
>> advanced routing policies in relation to 4-Byte ASNs. It is the tool =
that has
>> been missing since 4-octet ASNs were introduced.
>>=20
>> IANA has made an Early Allocation of the value 30 (LARGE_COMMUNITY) =
in
>> the "BGP Path Attributes" registry under the "Border Gateway Protocol
>> (BGP) Parameters" group.
>>=20
>> The draft can be read here: =
https://tools.ietf.org/html/draft-ietf-idr-large-community
>>=20
>> Additional information about Large BGP Communities can be found here:
>> http://largebgpcommunities.net/
>>=20
>> Starting today (2016.10.11), the following two BGP beacons are =
available
>> to the general public, with AS_PATH 2914_15562$
>>=20
>> Both these prefixes have a Large BGP Community attached:
>>=20
>> 2001:67c:208c::/48
>> 192.147.168.0/24
>>=20
>> Large BGP Community - 15562:1:1
>>=20
>> The NLNOG RING BGP Looking Glass is running the latest version of =
BIRD
>> which understands the Large BGP Community Path Attribute.
>>=20
>> IPv4 LG: =
http://lg.ring.nlnog.net/prefix_detail/lg01/ipv4?q=3D192.147.168.0/24
>> IPv6 LG: =
http://lg.ring.nlnog.net/prefix_detail/lg01/ipv6?q=3D2001:67c:208c::/48
>>=20
>> In theory, since this is an optional transitive BGP Path Attribute, =
all
>> the Looking Glass' peers should boomerang the Large Community back to
>> the LG. However we currently observe that 50 out of 75 peers =
propagate
>> the Large BGP Community to the LG.
>>=20
>> Relevant Router commands to see if you receive the attribute, or =
whether
>> one of intermediate networks has stripped the attribute from the =
route:
>>=20
>> IOS: show ip bgp path-attribute unknown=20
>> shows all prefixes with unknown path attributes.
>>=20
>> IOS #2 - like on route views:
>> route-views>sh ip bgp 192.147.168.0
>> BGP routing table entry for 192.147.168.0/24, version =
98399100
>> Paths: (39 available, best #30, table default)
>> Not advertised to any peer
>> Refresh Epoch 1
>> 701 2914 15562
>> 137.39.3.55 from 137.39.3.55 (137.39.3.55)
>> Origin IGP, localpref 100, valid, external
>> unknown transitive attribute: flag 0xE0 type =
0x1E length 0xC
>> value 0000 3CCA 0000 0001 0000 0001
>> rx pathid: 0, tx pathid: 0
>> =20
>> IOS-XR: (you must look at specific prefixes)
>> RP/0/RSP0/CPU0:Router#show bgp ipv6 unicast =
2001:67c:208c::/48 unknown-attributes=20
>> BGP routing table entry for 2001:67c:208c::/48
>> Community: 2914:370 2914:1206 2914:2203 2914:3200
>> Unknown attributes have size 15
>> Raw value:
>> e0 1e 0c 00 00 3c ca 00 00 00 01 00 00 00 01=20
>> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>=20
>> JunOS:
>> user@JunOS-re6> show route 2001:67c:208c::/48 detail=20
>> 2001:67c:208c::/48 (1 entry, 1 announced)
>> AS path: 15562 I
>> Unrecognized Attributes: 15 bytes
>> Attr flags e0 code 1e: 00 00 3c ca 00 00 00 01 00 00 00 01
>> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>=20
>> A note about router Configurations:
>>=20
>> Ensure you are not fitlering the path attributes, eg:
>>=20
>> JunOS:
>> [edit protocols bgp]
>> user@junos# delete drop-path-attributes 30
>>=20
>> XR:
>> configure
>> router bgp YourASN
>> attribute-filter group ReallyBadIdea ! avoid creating bogons
>> no attribute 30=20
>> !
>> !
>>=20
>> Contact persons: myself or Jared Mauch or NTT NOC. BGP Session
>> identifier 83.231.213.230 / 2001:728:0:5000::a92 AS 15562.
>>=20
>> Kind regards,
>>=20
>> Job
>>=20
