|
Thread Index [isp-bgp] RE: BGP advantages
On Tue, 7 Sep 2004, Dean Anderson wrote: > > > You need to have portable address space before BGP is going to useful. > > > > That's not entirely true. Multihoming to 2 or more providers using > > BGP to announce PA address space from one of your providers to all of your > > providers works just fine generally. The main disadvantage is you're > > still tied to that provider for the IPs and will have to renumber if you > > want to dump that provider. > > The more specific prefix will get advertised and used if both prefixes are > in table, but this isn't a /good thing/: It creates untenable route table > growth. You can imagine what might happen if another 100,000 companies > wanted to advertise /28's. Also some ISPs will reject small prefixes, or > won't accept non/16 prefixes from legacy class B space (verio). I don't think Verio's had those filters for years. ARIN rules allow for 1 provider for a multihomed customer to assign that customer a /24 regardless of IP usage. Filtering >24-bit prefixes is pretty common though AFAIK. What's the route table growth difference between advertising that PA /24 into the global table vs an old pre-ARIN portable /24 or a new ARIN assigned /22? Either way, one multihomed customer, one route. It only gets messier than ideally necessary when you keep growing (the typical ISP case) and end up with a bunch of various sized prefixes that all need to be advertised. ---------------------------------------------------------------------- Jon Lewis | I route Senior Network Engineer | therefore you are Atlantic Net | _________ http://www.lewis.org/~jlewis/pgp for PGP public key_________ To unsubscribe via postal mail, please contact us at: Jupitermedia Corp. Attn: Discussion List Management 475 Park Avenue South New York, NY 10016 Please include the email address which you have been contacted with.
Thread Index |
|
