Re: [Idr] FW: Large BGP Communities beacon in the wild

[Job Snijders <[e-mail]>]

Hi all,

Can anyone from Huawei help debug an issue?

It appears that some Huawei routers (at least NE40E with VRP 8.100) are
entirely ignoring route announcements which have a Large BGP Community
path attribute attached.

For testing, pingable beacon IPs: 192.147.168.255 / 2001:67c:208c::1

Not propagating an unknown optional transitive path attribute is one
thing, but outright dropping the entire route is a whole other level :)

Kind regards,

Job


On Tue, Oct 11, 2016 at 05:29:50PM +0200, Job Snijders wrote:
> This message was posted to various operational mailing lists.
> 
> TL;DR - there are now two beacons carrying a Large BGP Community in the
> DFZ. On IPv4 we observe full coverage from the NLNOG RING LG - on IPv6
> not so much.
> 
> Kind regards,
> 
> Job
> 
> ----- Forwarded message from Job Snijders <[e-mail]> -----
> 
> Date: Tue, 11 Oct 2016 17:01:56 +0200
> From: Job Snijders <[e-mail]>
> To: [e-mail], [e-mail], Jared Mauch <[e-mail]>
> 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 -----
> 
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