Hello,
You can define unique ASN for each routing instance on QFX for sure. BUT
@vicky12345 wrote:
I want to achieve complete segregation of bgp for each bgp instance running in virtual routers with different autonomous system number.
JUNOS routing instances do not provide "complete" separation, namely - they share the same Routing Process Daemon (RPD). Which means if a crafted packet is received in one routing instance and it crashes the RPD, then ALL routing instances are affected, irrespective of their ASN.
@vicky12345 wrote:
if we define autonomous numbers under routing-instance routing-option heirarchy, i hope there should not be any issue ?
It depends what do You call an "issue".
JUNOS AS path loop detection takes into account ALL ASN configured on local router, including routing instances and logical systems.
In other words, if BGP Update is originated by routing-instance A1 whose ASN is 64512 and it then gets into routing-instance B2 whose ASN is 64513, then routing-instance B2 will detect a loop. It may or may not be a "issue" for You depending on Your plans to trombone (or not) Your traffic thru this router.
HTH
Thx
Alex