Using 3G Dual Uplinks to Connect to the Internet

Because some branches are located in remote areas, it is difficult to deploy fixed networks. Or, the data service volume is limited, and using wired access is expensive. 3G access has become a better choice for these branches. In addition, these branches need network backup to ensure high network connectivity. The "3G network + 3G network" networking can provide highly reliable network backup. In this solution, primary links and backup links are connected to different carriers' 3G networks.

Figure 11-5 shows 3G dual link access of enterprise branches.

1. The router that supports 3G access, for example, the Router in Figure 11-5, is deployed in an enterprise branch.
2. The two 3G interfaces are configured as the primary and backup interfaces respectively, and they are connected to different carriers' networks.
3. IPSec is configured on both the primary and backup interfaces and IPSec VPN is created between the headquarters and branch. IPSec ensures secure data exchanges between the headquarters and branch.
4. The link connectivity detection function is enabled on the primary interface to check whether the link between the headquarters and branch is reachable. When a link fault is detected, the backup 3G interface is enabled to ensure the link connectivity between the headquarters and branch. The link connectivity detection function on the 3G primary interface keeps working. When the primary link recovers, the Router disconnects the backup link and switches traffic back to the primary link.
5. Based on branch services and network requirements, you can associate the link connectivity detection function with static routes and PBR, and use the 3G network to provide backup links. Load balancing is not recommended for traffic distribution on the two 3G interfaces.

Figure 11-5 3G dual link access of an enterprise branch