How to Set Up Two ISPs on One Switch

by Jonah Quant

In computer communications, a Local Area Network (LAN) can have multiple connections to external Internet Service Providers. This is typically done for fault tolerance--if one link falls, the LAN is still connected to the outside world through the other link--and for increased bandwidth. You can connect a single switch on your network to two ISPs.

Connect any of the "LAN" ports on the first router to a port in the switch. Connect the "WAN" port in the first router to the first ISP.

Connect any of the "LAN" ports on the second router to another port in the switch. Connect the "WAN" port in the second router to the second ISP.

Configure the first and second routers to NOT act as servers for the Dynamic Host Configuration Protocol (DHCP). The precise way of performing this step depends on the make and model of the routers.

Configure the first and second routers to use static Internet Protocol (IP) addresses. For example, assign addresses 192.168.1.1 and 192.168.1.2 to the two routers. The precise way of performing this step depends on the make and model of the routers.

Configure the LAN's DHCP server to hand out IP addresses in a range that does not include the routers. For example, configure it to hand out IP addresses in the interval 192.168.1.[3,254].

Configure some computers in the LAN to use one of the routers as a gateway to external addresses, while the remaining computers use the other router. For example, computers accounting for roughly half of the bandwidth needs should have "192.168.1.1" as their gateway, while the others have "192.168.1.2."

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About the Author

Jonah Quant has been writing about computer science since 1990. He has contributed to international conferences and journals such as those of the Institute of Electrical and Electronics Engineers and the Association for Computing Machinery. Quant has a Ph.D. in computer science from the University of California.