A friend asked me today, what is the sense of 2 virtual VPN network interfaces or 2 VPN gateways.
Classic VPN connecting business locations
In the classic way at golden millenium, companies wanted to connect their business locations with VPN, because internet access with a huge bandwidth became very cheap, because of liberalisation of internet and ISDN connections between different business locations still left expensive, when connections were 24/365 open.
Instead of avoiding all permanently broadcasting services, that are not fundamentally needed (like rwho), some of the companies bought a powertimer at low costs to avoid NT-Domain pings and other broadcasts.
In that time arround the golden millenium, VPN (virtual private network) became a more popular expression and since some companies invested in IPSec (FreeSwan) or PPTP GRE VPN technology,
many companies also wanted to have this.
Furthermore a backup internet connection became often cheaper as an ISDN backup over normal phone lines. Cable providers and XDSL providers had very special offers at the time.
All VPN traffic is routed through headquater location green
In that scenario, a headquater with (l-1) virtual vpn interfaces routes all traffic to all other location.
Classic central star network topolgy, where each not headquater location only need 1 vpn virtual network interface.
The advantage of that scenario is, that location green can make more complete rules at the firewall and vpn routing, which packages are to route.
Disadvantage of that scenario is, that IPX/SPX tunnels over ipsec/pptp tunnel over internet became very slow with huge package loss.
All over cloud provider VPN gateway
Today companies often uses a VPN cloud gateway from a cloud provider to route their traffic between different locations.
Advantage is, that the cloud provider might guarantee a 24/356 availibility and that huge cloud providers offer up to 32 backup gateways, if you need to route hurtig.
Disadvantage in that scenario is, that the cloud provider VPN gateway is same as the headquater in example before.
