FYI ----- Forwarded message from Job Snijders <job@ntt.net> ----- Date: Tue, 11 Oct 2016 17:01:56 +0200 From: Job Snijders <job@ntt.net> To: nanog@nanog.org, routing-wg@ripe.net, Jared Mauch <jmauch@us.ntt.net> Subject: [routing-wg] Large BGP Communities beacon in the wild Dear all, Large BGP Communities are a novel way to signal information between networks. An example of a Large BGP Communities is: 2914:4056024901:80. 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. 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. The draft can be read here: https://tools.ietf.org/html/draft-ietf-idr-large-community Additional information about Large BGP Communities can be found here: http://largebgpcommunities.net/ Starting today (2016.10.11), the following two BGP beacons are available to the general public, with AS_PATH 2914_15562$ Both these prefixes have a Large BGP Community attached: 2001:67c:208c::/48 192.147.168.0/24 Large BGP Community - 15562:1:1 The NLNOG RING BGP Looking Glass is running the latest version of BIRD which understands the Large BGP Community Path Attribute. IPv4 LG: http://lg.ring.nlnog.net/prefix_detail/lg01/ipv4?q=192.147.168.0/24 IPv6 LG: http://lg.ring.nlnog.net/prefix_detail/lg01/ipv6?q=2001:67c:208c::/48 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. Relevant Router commands to see if you receive the attribute, or whether one of intermediate networks has stripped the attribute from the route: IOS: show ip bgp path-attribute unknown shows all prefixes with unknown path attributes. 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 IOS-XR: (you must look at specific prefixes) RP/0/RSP0/CPU0:Router#show bgp ipv6 unicast 2001:67c:208c::/48 unknown-attributes 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 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ JunOS: user@JunOS-re6> show route 2001:67c:208c::/48 detail 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 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ A note about router Configurations: Ensure you are not fitlering the path attributes, eg: JunOS: [edit protocols bgp] user@junos# delete drop-path-attributes 30 XR: configure router bgp YourASN attribute-filter group ReallyBadIdea ! avoid creating bogons no attribute 30 ! ! Contact persons: myself or Jared Mauch or NTT NOC. BGP Session identifier 83.231.213.230 / 2001:728:0:5000::a92 AS 15562. Kind regards, Job ----- End forwarded message -----