Hi Rene, please help me understand the basic concept behind why we need BGP.
Here’s an excerpt from your tutorial:
“In my previous examples we got public IP addresses from our ISP. Now I’m connected to two different ISPs so what public IP addresses should I use? From ISP1 or ISP2? If we use public IP addresses from ISP1 (or ISP2) then these servers will be unreachable once the ISP has connectivity issues.”
Customer’s default gateway has dedicated links that connect to each ISP. Why can’t customer advertise 2 default routes using 2 different Public IPs received from the 2 different ISPs? So, even if one ISP fails, internet traffic will still reach the customer through the other ISP. Customer can do NAT/PAT at the default gateway.
- So, why should customer get their own Public IP space?
- Even if the customer gets their own Public IP space from IANA, why can’t they do default routing there too? Why do they need BGP at all, other than the fact that they can play around with BGP path attributes?