[c-nsp] received-only in BGP output

[Antonio Querubin]

On Fri, 28 Apr 2006, Richard Mikisa/Bushnet wrote:

> Below is the show BGP output from the telia looking glass for network
> 41.220.0.0/20. What does the received-only mean?

If a router has soft inbound configuration enabled, then it can store the 
received prefixes in a separate cache from the actual forwarding table.

> I ask because I have noticed that output from some looking glasses has 
> it and others don't. Can it be the reason why I can't get to certain 
> sites like cnn.com while I can get to others.

If a route is only showing up as received-only and nowhere else in your 
forwarding table AND you have no default route then you might not have a 
way to reach that site.

> BGP routing table entry for 41.220.0.0/20, version 23211151
> Paths: (3 available, best #2)
>  Advertised to update-groups:
>     1          3
>  1299 29032
>    194.255.253.6 (metric 10) from 194.255.253.6 (194.255.253.6)
>      Origin incomplete, metric 0, localpref 100, valid, internal
>      Community: 1299:1000
>  1299 29032
>    213.248.66.73 from 213.248.66.73 (80.239.146.13)
>      Origin incomplete, localpref 100, valid, external, best
>      Community: 1299:1000
>  1299 29032, (received-only)
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>    213.248.66.73 from 213.248.66.73 (80.239.146.13)
>      Origin incomplete, localpref 100, valid, external
>      Community: 1299:1000 1299:30000 1299:30100

The router does have a useable path (#2).  The two nearly identical 
entries may be due to some community re-writing.