Hei Rene,
Thanks for the lesson, in my working experience, i am stuck in a situation for 2 sites. i have the ebgp peering up, but i am receiving 0 prefix from my isp. The isp said when they show ip bgp nei adverticed route that are hundreds of routes advertised, they can receive our route. Any good debug command to troule should this? We have plain bgp config, the same config (different peering ip though) is working with other sites.
One interesting thing is that when i ping the isp with mtu 1500 it does not work, but it works with 1496. After reading cisco doc, there was a solution which is changing the ip tcp adjuest-mss to 1000 it helps with one location but the other one still has no luck.