[158807] in North American Network Operators' Group
Re: RADB entry
daemon@ATHENA.MIT.EDU (Courtney Smith)
Tue Dec 11 21:09:54 2012
From: Courtney Smith <courtneysmith@comcast.net>
In-Reply-To: <00ea01cdd7fc$9e5f5270$db1df750$@gmail.com>
Date: Tue, 11 Dec 2012 21:09:40 -0500
To: Chuck Church <chuckchurch@gmail.com>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
Chuck,
If you look at the communities on 68.115.27.0/24 you will see 7018:5000. =
That community means AS209 is a AT&T peering partner. =20
> route-server>sh ip bgp 68.115.217.201
> BGP routing table entry for 68.115.217.0/24, version 13683280
> Paths: (18 available, best #7, table Default-IP-Routing-Table)
> Not advertised to any peer
> ...
> 7018 209 20115, (aggregated by 20115 96.34.212.29), (received & used)
> 12.123.1.236 from 12.123.1.236 (12.123.1.236)
> Origin IGP, localpref 100, valid, external, atomic-aggregate, =
best
> Community: 7018:5000 7018:37232
Now if you look at results for 75.77.38.0/23 you will see 7018:2000. =
That would mean AS7029 is an AT&T customer. =20
> route-server>sh ip bgp 75.77.38.0
> BGP routing table entry for 75.77.38.0/23, version 26960376
> Paths: (19 available, best #7, table Default-IP-Routing-Table)
> Not advertised to any peer
> 7018 7029 26296 26296 26296, (received & used)
> 12.123.1.236 from 12.123.1.236 (12.123.1.236)
> Origin IGP, localpref 100, valid, external, best
> Community: 7018:2000 7018:34011
In AT&T's network, I believe they apply local pref 80 for peer routes =
and local pref 100 for customer routes. Ignore the local pref values =
you see on the route server.
Let's look at what appears to be going on. Per your earlier post, you =
verified Charter(AS20115) has the prefix. Charter does not appear to =
have a interconnect with AT&T(7018) so they send to =
Centurlink/Qwest(AS209). We see Centurylink(AS209) accepts per their =
looking glass at =
https://kai04.centurylink.com/PtapRpts/Public/BackboneReport.aspx.
BGP routing table entry for 75.77.38.0/23
20115 26296
Nexthop 205.171.0.93 (via 207.109.19.150) from chi-core-01 =
(205.171.0.144)
Origin IGP, metric 0, localpref 100, internal, valid
Last update: 13:30:09 ago
Communities: 209:209 209:14520 20115:3200 20115:63004
Originator Id: 205.171.0.93
Cluster ID List: 207.109.19.145 205.171.0.149
Now Centurylink(AS209), sends the /23 to their peer AT&T(AS7018). AT&T =
accepts the /23 from Centurylink. Since Centurylink is their peer, AT&T =
assigns local pref 80. That's lower than the 100 assigned to the =
Windstream. Highest local pref wins. Your prepends are never part of =
the decision. So AT&T continues to pref the path via their customer =
Windstream(AS7029). =20
I suspect this is really your problem instead of route registry data. =
Hopefully, Windstream offers their customers some BGP communities to =
allow traffic engineering. =20
Finally, the WISP has a AS number from ARIN, they should be able to =
create their own maintainer on rr.arin.net. The RADB fee might be a =
little much for your WISP. https://www.arin.net/resources/routing/
Make sense?
=20
On Dec 11, 2012, at 7:07 PM, Chuck Church wrote:
> Courtney,
>=20
> This is from the AT&T 7018 route server. The first one is our =
WAN
> IP address, part of our ISP's ASN. The second one is our own /23. =
The
> first one goes through Century Link, then Charter. The second one I =
would
> think would take same path, with one additional AS (our own). But =
that one
> isn't present at AT&T. Level 3 shows the same thing. Century Link
> themselves see our /23 through Charter...
>=20
> route-server>sh ip bgp 68.115.217.201
> BGP routing table entry for 68.115.217.0/24, version 13683280
> Paths: (18 available, best #7, table Default-IP-Routing-Table)
> Not advertised to any peer
> ...
> 7018 209 20115, (aggregated by 20115 96.34.212.29), (received & used)
> 12.123.1.236 from 12.123.1.236 (12.123.1.236)
> Origin IGP, localpref 100, valid, external, atomic-aggregate, =
best
> Community: 7018:5000 7018:37232
>=20
> route-server>sh ip bgp 75.77.38.0
> BGP routing table entry for 75.77.38.0/23, version 26960376
> Paths: (19 available, best #7, table Default-IP-Routing-Table)
> Not advertised to any peer
> 7018 7029 26296 26296 26296, (received & used)
> 12.123.1.236 from 12.123.1.236 (12.123.1.236)
> Origin IGP, localpref 100, valid, external, best
> Community: 7018:2000 7018:34011
>=20
>=20
> Thanks,
>=20
> Chuck
>=20
>=20
> -----Original Message-----
> From: Courtney Smith [mailto:courtneysmith@comcast.net]=20
> Sent: Tuesday, December 11, 2012 5:38 PM
> To: nanog@nanog.org
> Subject: Re: RADB entry
>=20
>=20
>>=20
>> Anyone,
>>=20
>>=20
>>=20
>> Hopefully this is a simple question about RADB. I'm=20
>> supporting a small wireless ISP, they just recently added a second=20
>> upstream connection - Charter (AS 20115). The IP space was =
originally=20
>> issued by the other upstream Windstream (AS 7029). Looking at a few=20=
>> resources such as the bgp.he.net to see who peers with who and =
looking=20
>> glasses, it seems that not all of AS 20115 peers are accepting our=20
>> prefix. AT&T is an example - AS7018. In one case, it's an upstream =
2=20
>> levels up - Century Link accepts from Charter, but Level 3 doesn't=20
>> accept it from Century Link. Charter uses RADB. The entry for the =
prefix
> looks like this:
>>=20
>>=20
>>=20
>=20
> What makes you think Level3 is not accepting from CenturyLink? I =
suspect
> Century Link may be a peer of Level3 instead of a customer. =
Windstream
> appears to be a customer of Level3. Level3 will put a higher local =
pref on
> customer routes.
>=20
>=20
>=20
> Courtney Smith
> courtneysmith@comcast.net
>=20
> () ascii ribbon campaign - against html e-mail=20
> /\ www.asciiribbon.org - against proprietary attachments
>=20
>=20
>=20
Courtney Smith
courtneysmith@comcast.net
() ascii ribbon campaign - against html e-mail=20
/\ www.asciiribbon.org - against proprietary attachments
