BGP full and partial routes

[a.manosca]

Hi all,

I'd like to know the effects of using full or partial BGP routes in a small ISP's GW router besides the reduced router memory consumption?

I mean, if I'm receiving full Internet BGP routes from a bigger ISP, is there a noticeable difference if I'm only receiving partial internet routes? (e.g., faster connections to remote servers on the net because my router already has the complete route to these servers through the full BGP route).

Thanks...

[donewald]

The effects with more routes is not only a resource issue as you've mentioned but it's actually slower. Since destinations are looked by by longest match, if you've got 200,000 routes to go through your router will take longer to come up with a match rather than you having local routes and allowing only a default, or just a small subset of specifics you need.

If you don't need the specifics, don't take them. They'll do you no good.

Hope this helps,

Don

[a.manosca]

Thanks for the reply, but I do have some follow-up questions to be more specific:

1. If the ISP has many dial-up users connecting to them, let's say around 2,000-3,000 simultaneously browsing the web plus the corporate customers also using the internet (so maybe this is not a small ISP anymore), would it be better to have full BGP routes?

2. Is it still recommended to use partial routes if the ISP has another customer peering with them through BGP with their own registered AS number to access the internet?

Thanks again.

[donewald · Accepted solution]

1. It would fully depend if this ISP would benefit from having all specifics. This would more than likely not be the case if the ISP was not an ISP for others (UUNET/Qwest/etc). If there are several paths out of the ISP to the Internet Core then it might be useful to have specifics to ensure the most optimal path was taken to the destination.

2. Again this would depend on a couple of things:

a. if your customer requires full routes for some reason then you would require them to provide them.

b. if your customer does not require them and you don't, for above mentioned reason, then you could just send your customer a default (0/0) and advertise thier networks up to your provider.

Hope this helps,

Don

[a.manosca]

Thanks a lot, Don...