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Thread Index [isp-bgp] Introduction, and questions
Hi everyone, I'm a network engineer for a company based in The Netherlands. I've recently started to use BGP with my upstream, and we announce a /20. At the moment, our configuration is very simple, since we don't do any transit or multi-homing, although this is going to change in just a few months, because we are getting a second upstream. I am a newbie with BGP, so there are some things that I am not too clear about. Perhaps someone with more experience can guide me. At the moment, we have a customer using a /22 and a /23 from our /20 assignment from RIPE. For various complex reasons this customer is moving to another provider, but needs to keep their IP addresses. If the other provider announces those /22 and /23 blocks via their AS, is that ok? Do I need to break up my /20 announcement into a /21 and /23? I have read that BGP will choose the most specific prefix, so if I understand it right, then I should be able to leave my /20 in place, while the customer can announce their more specific routes via the other provider. Can someone confirm this for me? Secondly, I have read that many providers often filter received routes, and typically reject anything more specific than a /22. We don't do that, so in our BGP table, I see many /24 networks too. May I hear opinion on what is common practice on the Internet these days? Since routers nowadays have more memory and power, is it necessary to filter more specific routes? I ask this question to understand the implications of what will happen to our customer when they announce their routes via the other provider, particularly the /23 they have. Thanks in advance to everyone for your valuable opinions. -- Anand Buddhdev http://anand.org
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