Chapter 14 IPSec VPN

Figure 219 VPN Topologies

Hub-and-spoke VPN reduces the number of VPN connections that you have to set up and maintain in the network. Small office or telecommuter IPSec routers that support a limited number of VPN tunnels are also able to use VPN to connect to more networks. Hub-and-spoke VPN makes it easier for the hub router to manage the traffic between the spoke routers. If you have the spoke routers access the Internet through the hub-and-spoke VPN tunnel, the hub router can also provide content filtering, IDP, anti-spam and anti-virus protection for the spoke routers.

You should not use a hub-and-spoke VPN in every situation, however. The hub router is a single point of failure, so a hub-and-spoke VPN may not be appropriate if the connection between the spoke routers cannot be down occasionally (for maintenance, for example). In addition, there is a significant burden on the hub router. It receives VPN traffic from one spoke, decrypts it, inspects it to find out where to send it, encrypts it, and sends it to the appropriate spoke. Therefore, a hub-and-spoke VPN is more suitable when there is a minimum amount of traffic between spoke routers.

14.20.1 Hub-and-spoke VPN Example

The following figure shows a basic hub-and-spoke VPN. Branch office A uses one VPN rule to access both the headquarters (HQ) network and branch office B’s network. Branch office B uses one VPN rule to access both the headquarters and branch office A’s networks.

 

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