Routing

General routing question:

2 Sites.....

Site 1:

MX240 --- IP Range 192.168.10.0/30

MX240 -- IP Range 192.168.10.4/30

SRX1500 -- IP Range 192.168.10.8/30

For eBGP we aggregate these routes into a /24 for upstream ISP peer to accept....

Site 2:

MX240 --- IP Range 192.168.10.12/30

MX240 --- IP Range 192.168.10.16/30

SRX1500 --- IP Range 192.168.10.20/30

Again, for eBGP to a separate upstream provider we need to aggregate and advertise to a /24

So, my question here is..... if we have 1 x VPN to one site with a 192.168.10.xxx/30 address and another VPN on the other site with a 192.168.10.xxx/30 address..... but these are to two different upstream ISP providers.... how do we differentiate the two sites once aggregation takes place as they both will fall under the same /24 prefix? It would be an extremely wasteful usage of address space if we have to place one /30 into one /24 range and the other /30 into a completely separate /24 range..... I am hoping that the aggregation takes into account the "Live" subnets within the /24 and routes respectively.

No, there is no account for the smaller subnets.  Once you roll this up into an aggregate for the internet table anything in the entire 24 then can be delievered to either site.  The only route either ISP or their connected peers have is the entire 24.

Hi Spuluka

Thank you for the response. This is exactly what I thought and that either VPN would be accessible in the same /24, albeit a /30.

Thanks again.