There are numerous show commands using Cisco IOs to verify interface settings, operation, and configuration. The following three commands are very useful to identify an interface status especially when we are using the IPv4 address:
Verify Interface settings for IPv4 Addresses
show ip interface brief – The show ip interface brief is one of the most frequently used commands in the Cisco devices. This command provides abbreviated output than the show ip interface. It provides an outline of the key information for all the network interfaces on a router. The figure below illustrates the output of this command. The output displays all interfaces on the router; the IP address assigned interfaces if any. It is also showing the operational status of the interface. The command also verifies the status of the switch interfaces. The figure below displays the output of show ip interface brief command.
show ip route – The show ip route command displays the routing table of the router. The routing table is the list of all networks where the router can communicate; their metrics and how to communicate with them. We can also use abbreviated command instead of full command. The abbreviated command is sh ip ro. The command also has parameters after route (ro) like sh ip ro rip for all RIP routes. The figure below display the output of show ip route. figure 2 displays the output of the show ip route command. There are three directly connected network entries and the one EIGRP router entry. We will also discuss the parameters of the routing later in the coming article.
show running-config interface interface-id– The show interface command with interface-id displays the specific interface with configuration and statistics. This command interface and interface-id give a lot of information in the output.
show interfaces – We can also use this command to show interface information and packet flow count for all interfaces on the device. It displays all type of interfaces with configuration and statistics. This command provides a lot of information in the output. The abbreviation of this command sh int. The figure below illustrates the output of the show interface command.
show ip interface – We can also use this command to show the IPv4 related information for all interfaces on a router.
Verify interface settings for IPv6 Addresses
We can also verify interface setting and configuration for IPv6 addresses using similar commands with little changes in IPv4 verification commands.
The show ipv6 interface brief command in Figure 3 giving a result for the interfaces. The up/up indicates the Layer 1/Layer 2 interface state. This is equal as the Status and Protocol columns in the equivalent IPv4 command already showing in figure1.
The figure illustrates two configured IPv6 addresses for each interface. The IPv6 global unicast address is manually configured and the second address, which begins with FE80, is the link-local unicast address for the interface. When someone configures a global unicast address on an interface, the link-local address is automatically added to this interface. The global unicast address is not necessary for the network but a link-local address is necessary for each network interface.
The show ipv6 interface FastEthernet 0/0 command displays the interface status and all of the IPv6 addresses to the interface. It also shows a link-local address and global unicast address including multicast addresses assigned to the interface, beginning with prefix FF02.
The show ipv6 route command display and verify IPv6 networks and specific IPv6 interface addresses in the IPv6 routing table. The show ipv6 route will only display IPv6 routes. The ping command is the same for both IPv4 and IPv6 interfaces. The ping command verifies Layer 3 connectivity.