A network engineer is troubleshooting a small LAN network with one border router, GW01 that connects to the Internet Service Provider's (ISP) network....

A network engineer is troubleshooting a small LAN network with one border router, GW01 that connects to the Internet Service Provider's (ISP) network. GW01 uses its Serial 0/2/1 interface to connect to the ISP's router. Everyone on the LAN network lost connectivity to the Internet. Upon troubleshooting the issue, the network engineer notices the following message after typing show ip route.

Gateway of last resort required but not set.

What do you suggest the network engineer do to rectify this issue? Assume the problem is only on the organization's LAN side of the network. Provide as much information as possible including specific commands and all required parameters.