RADB entry

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1

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

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2

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?