Which Cisco IOS command is used to display information about all IPv4 routing protocols running on a router?

The command used to display information about all IPv4 routing protocols running on a router is "show ip protocols." This command provides a detailed overview of the routing protocols that are currently configured and operational on the device, including information such as protocol type (e.g., RIP, OSPF, EIGRP, etc.), router IDs, timers, networks being advertised, and much more.

This comprehensive output is vital for network administrators when troubleshooting or optimizing the routing configuration on the router. It allows them to understand which protocols are actively participating in routing decisions and to verify that those protocols are correctly configured and operational.

In contrast, other commands do not serve this specific function. For instance, "show ip interface" is used to display the status and configuration of each interface, while "show routing path" is not a recognized command in Cisco IOS. The command "show ip routing" displays the current routing table rather than the routing protocols themselves, making it less appropriate for identifying and examining the routing protocols that are in use.