Martin T wrote:
let's assume that there is an ISP "A" operating in Europe region who has /19 IPv4 allocation from RIPE. From this /19 they have leased /24 to ISP "B" who is multi-homed. This means that ISP "B" would like to announce this /24 prefix to ISP "A" and also to ISP "C". AFAIK this gives two possibilities:
1) Deaggregate /19 in ISP "A" network and create "inetnum" and "route" objects for all those networks to RIPE database. This means that ISP "A" announces around dozen IPv4 prefixes to Internet except this /24 and ISP "B" announces this specific /24 to Internet.
2) ISP "A" continues to announce this /19 to Internet and at the same time ISP "B" starts to announce /24 to Internet. As this /24 is more-specific than /19, then traffic to hosts in this /24 will end up in ISP "B" network.
Excuse me for intruding on American Operators from Siberia, but I find this topic very interesting. I have reports that in case (2), some operators (e.g. Rostelecom) don't accept the /24 or even /23 prefix on the grounds that it is part of a larger /19 route already present in the routing table. Could they have a reason not to accept these more specific prefixes other than a whim? -- Victor Sudakov, VAS4-RIPE, VAS47-RIPN sip:sudakov@sibptus.tomsk.ru