On Thu, Jun 26, 2003 at 09:50:45AM -0600, Aaron Dewell wrote: > On Thu, 26 Jun 2003, Tomas Bonnedahl wrote: > > i dont have any addresses nor do i own an AS, i know there are private ASNs to > > use but this seems like a more complicated solution than a mere multipath default > > route to the two upstream providers. > An ASN can be gotten from ARIN with the justification "I'm multihomed to ASN #X > and #Y" and $500. Or you can use a private AS and have your upstreams filter > it out, also reasonably common. i didnt know it was that easy really, this might be an option. > BGP is not complicated at all to use, that's a myth. It's a fairly simple > protocol, and even easier to set up. Define one external peer per router, one > internal peer (each other), this is all done by AS. Set up the routes you want > advertised. In this case, you want everything, so no inbound filtering. Done. > 3 configuration options in Zebra's bgpd. Less complicated than setting up NAT. i assume i will only advertise the core (some /28) since the lan is still a private network. i probably wont be able to get a whole /24 from my upstream. > Think about it - if you have two IP addresses total, one assigned by each > upstream, and using two default routes, anything connection-oriented is > broken immediately (TCP comes to mind). Anything connectionless (i.e. UDP) > will likely work fine. Web, ssh, IMAP, POP3, SMTP are all TCP. Those not > working make it basically useless. why wont it work? from what i understand, you could get a "per flow" with julians patches so the core-router doesnt varies on a per packet basis and thus make established connections to fail. > Otherwise, you have to have selective routes. Route this block of the internet > through provider X, that block through provider Y. No failover, no redundancy, > no point. Or, you could point default and provider X and a lower priority to > provider Y, but then you have to learn by IGP at your core when provider X dies. > That means advertising default from the borders with your IGP, which is a > workable solution, but could get messy if you're not pretty good at whatever > IGP you are using, making the assumption that your IGP will do it. However, > two problems: 1. Your second connection is idle until the primary fails, thus > wasting money. 2. All TCP connections reset when you fail over to the backup, > and reset again when you resume to the primary. i thought the multihop path was designed to solve this issue with redundancy and failover? my very first thought in this was to use ospf as IGP but i couldnt come up with something to use upstream to see if the providers still were under normal operation. just to sum it up: use something like ospf as IGP and use BGP upstream. were you assuming that i would get a /24 from my isp and use for lan or should i do nat on the core router from the lan? thanks, tomas
