On 2010-05-20 11:25, Rafael Ganascim wrote:
Hi all,
I have a doubt about the bellow scenario, where the ISP1 use eBGP
sessions to its peers and is a BGP Transit AS.
NSP 1 ------------------ ISP 1 Router2 ----------- NSP 2
| |
| |
| |
| annunce /21 |
| |
Customer1 --------------- ISP 1 Router1
announce /20
The "Customer1" is client on both ISPs (ISP1 and NSP1) and have an /20
IP prefix. To NSP1, it announce two /21 prefixes. To ISP1, it announce
a /20 prefix. If traffic comes from NSP 2 (connected only to ISP 1) to
Customer1, the ISP 1 Routers try to send data over NSP 1, ignoring the
Custormer1->ISP1 link.
To solve this question, an solution that I found is filter Customer1
prefixes in BGP session between NSP1 and ISP1 Router2. But this don't
appear scalable...
longest match wins...
if you're customer 1
deaggregate the avertisement to isp 1 or re-aggregate the advertisement
to nsp 1. either will achieve the same end.
if you're isp1 consider what customer 1 was trying to achieve by doing
this. e.g. they're traffic engineering (or they are clueless) and
theirfore have a vested interest in the current path.
Is this solution right ? What is the better solution for this
scenario? How large ISPs solve this kind of problem?
Thanks,
Rafael
