multihoming with BGP

[donlon]

Hello all

Am hoping to get some info and advice to sort out a possible multihoming implementation.

Scenario: Have separate 3725 with 256MB of memory, each connected to different ISPs. An E-commerce site, we're more concerned with high-availability rather than load-sharing (although both would be nice).

We can get a class C from one of the Service Providers (ISP A), my concern is the advertising via ISP B.
Assuming they advertise our class C via BGP ---
how likely is a class C route to get propagated throughout the Internet without some major Providers filtering it for being too small a block? Being an E-commerce site, if our primary connection to ISP A goes down, the redundant link is of limited usefulness if say... 30% of the Internet doesn't know how to route to us (because some Providers drop our /24 prefix).

Comments?

 

[baddos]

Here is what you need...

You need to register with ARIN for your own AS number.

You need to have the ISP that gave you the /24 "swipe" it to you... Basically it means that the ISP stills owns it, but has given you the right to use it. When you look it up on ARIN's whois, it will have both you and the ISP as contacts.

Once you have the /24 swiped, then you can contact the provisioning guys of ISPB to allow you send your /24 to them. They won't accept a subnet from you unless it's swiped to you.

Once setup correctly you'll advertise it to your two ISPs... Depending on the ISP, they might still aggregate it, but on a /24 you should be fine.

After it's setup... Check it out on a couple of free route servers, to make sure you see your /24 coming from two different AS Paths.

You should be good... The people that don't accept /24s will still have an aggregate to your ISP's larger block... Once it gets down the line, some router will see both paths and know how to forward. I can't think of a scenario where it wouldn't function correctly under these circumstances.

 

[nyy1023]

what was said above is right, but You MUST have your own ASN in order to be multihomed. The /24 issues should not be a problem anymore, but like you were suggested above you can look through different looking glasses to see if your block is being propogated throughout the internet.

but you must have your ASN and that takes about 30 days to get, maybe faster depends on how busy they are but the typical turnaround has been 30 days. You might also want to get your own block of IP's too.