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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: oh k can you see
Maybe I'm missing something, but the core issue is that the NO- EXPORT'ed anycast instance has a higher localpref inside the AS it's being advertised to, and as such supressing the non-NO_EXPORT'ed prefix. The "exportable" prefix gets suppressed at a point on the network such that the peering routers never see it, so it never makes it out of that AS. Advertising the NO-EXPORT as a /25 (or two /25s) would serve the same purpose as tagging it NO-EXPORT, because as you say most peers filter on the /25. Incidentally it would obviate the need to assign it a higher localpref because it's a shorter prefix. However, unless I'm misunderstanding something, the /25 would not preempt the /24 advertisement, so the /24 would still make it out of the AS. Just make sure you don't have anything numbered x.x.x.127 on the block... On Nov 2, 2005, at 8:42 AM, Randy Bush wrote: Is it an idea to have anycasted instances using NO_EXPORT announce /25's instead of /24's?many many folk filter on /24, so the /25 would not be seen. Isn't that the point? The existing /24 is tagged NO-EXPORT after all... Another possibility is for $LARGE_ISP to localpref the NO_EXPORTED down to $LOW valueand then how will the down-preffed prefix be seen within $large_isp? local-pref is a very heavy hammer. randy, at the clue edge i guess -C
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