Large BGP Communities beacon in the wild

Baldur Norddahl baldur.norddahl at gmail.com
Tue Oct 11 17:31:13 UTC 2016


Hi

This looks like this on the ZTE M6000 platform:

ballerup-edge1#show bgp vpnv4 unicast vrf internet detail 192.147.168.0 
255.255.255.0
BGP routing table entry for 192.147.168.0/24
25w4d received from 149.6.136.169 (154.26.32.23), path-id 0
    Origin i, nexthop 149.6.136.169, metric 100, localpref 100,weight 0, 
rtpref 200, best, block best, selected,
    Community 174:21100 174:22010 60876:174
*Unknown attribute type 30 flag e0 len 12*
    As path [174 2914 15562]
    As4 path
    Received label  notag

25w4d received from 216.66.83.101 (216.218.252.202), path-id 0
    Origin i, nexthop 216.66.83.101, metric 25, localpref 100,weight 0, 
rtpref 200,
    Community 60876:6939
*Unknown attribute type 30 flag e0 len 12*
    As path [6939 1299 2914 15562]
    As4 path
    Received label  notag



Regards,

Baldur

Den 11/10/2016 kl. 17.01 skrev Job Snijders:
> 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 at 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 at 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



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