nanog: Re: RADB entry

[Courtney Smith <courtneysmith () comcast net>]

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.  

> 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.  

> 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).  

I suspect this is really your problem instead of route registry data.  Hopefully, Windstream offers their customers 
some BGP communities to allow traffic engineering.  

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?

 
On Dec 11, 2012, at 7:07 PM, Chuck Church wrote:

> Courtney,
>
>       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...
>
> 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
>
> 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
>
>
> Thanks,
>
> Chuck
>
>
> -----Original Message-----
> From: Courtney Smith [mailto:courtneysmith () comcast net] 
> Sent: Tuesday, December 11, 2012 5:38 PM
> To: nanog () nanog org
> Subject: Re: RADB entry
>
>
> > Anyone,
> >
> >
> >
> >               Hopefully this is a simple question about RADB.  I'm 
> > supporting a small wireless ISP, they just recently added a second 
> > upstream connection - Charter (AS 20115).  The IP space was originally 
> > issued by the other upstream Windstream (AS 7029).  Looking at a few 
> > resources such as the bgp.he.net to see who peers with who and looking 
> > glasses, it seems that not all of AS 20115 peers are accepting our 
> > prefix.  AT&T is an example - AS7018.  In one case, it's an upstream 2 
> > levels up - Century Link accepts from Charter, but Level 3 doesn't 
> > accept it from Century Link.  Charter uses RADB.  The entry for the prefix
> looks like this:
> >
> 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.
>
>
>
> Courtney Smith
> courtneysmith () comcast net
>
> ()  ascii ribbon campaign - against html e-mail 
> /\  www.asciiribbon.org   - against proprietary attachments
Courtney Smith
courtneysmith () comcast net

()  ascii ribbon campaign - against html e-mail 
/\  www.asciiribbon.org   - against proprietary attachments