BGP Route Filtering

Hi everyone,

We're using Juniper, but I doubt that matters at all for this question. And I will add both ISPs only offer default or full table, neither offers customer routes.We currently have two connections one is BIG-ISP one is SMALL-ISP. Very self explanatory. Small-isp we've had for a year and was the first connection we enabled BGP on and we took full route.Some weeks later we turned up big-isp and took default. Our static route is primary the big-isp and second small-isp.

We're mostly inbound so really it doesn't matter very much, but if I am going to do this I want to do it right. We're also running 90% full on memory with 1 full table so taking 2 full tables is out of the question without buying hardware.

My plan was to look up all prefixes from small-isp and create a route filter that allows all those prefixes, then drop everything else. This means we will use small-isp for their routes (which essentially is this country which they have very well covered), and then everything else will use big-isp. If either go down we still have internet connection.

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Does this sound sane? My only problem with this is it obviously won't auto-update. This led to to think there is a better way of doing this to only accept customer routes from small-isp, however my knowledge of BGP breaks down at this point.

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Thanks

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*re-posted due to title typo*