[c-nsp] BGP long prefix ads

[Roman Bestuzhev]

Hello,

We have our AS and block of /21 and we are connected to two ISPs. One of
them is the main, the other is backup. All traffic is going trough the main
one and if it fails the backup is used. This behaviour was implemented by
using prepending and works good.

I am thinking about load balancing between both ISPs. I have read about a
technique when you divide your block to several pieces, for example to two
/22 blocks and advertise one of them to one ISP and other block to another
ISP and at the same time advertise whole prefix to both ISPs, /21 in this
case. This leads to getting incoming traffic trough both providers and you
can control which subnets in your AS connect to Internet trough which ISP.

My question: is this scheme used widely and would this scheme work well in
real Internet for /22 prefixes, for /23? For example, is there any
possibility to loose connectivity to some parts of Internet in case of
filtering of long prefixes by Internet Providers? Are there other drawbacks
of this?

Thanks in advance for any ideas and advises,


--
Roman Bestuzhev,
System Administrator