Hello Faizan,

if you mean what routes you shouldn't accept on an eBGP session describing Internet the routes that shouldn't be accepted are called bogons:

you should at least:

deny = not accept your own public prefixes

deny = not accept any private IP address as per RFC 1918

see for more information

http://www.nanog.org/mtg-0501/pdf/deitrich.pdf

if instead you mean what routes are good in a BGP table just check the first lines of show ip bgp

installed routes are also present in the routing table in the BGP table are marked as:

>*

example

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal

Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path

*>i3.0.0.0 xx.yy.5.178 70 0 701 80 i

* zz.kk.234.137 70 0 3549 701 80 i

the first path is preferred

Hope to help

Giuseppe