cisco show interface

How to Verify Interface Settings

How to Verify Interface Settings

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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.

Verify Interface Settings

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 displays 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 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 settings 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.

Cisco Router Interface Configuration: CLI Guide, IPv6 Setup & Troubleshooting (2025 Update)

Cisco Router Interface Configuration: CLI Guide, IPv6 Setup & Troubleshooting (2025 Update)

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Properly configuring Cisco router interfaces is critical for network performance, security, and scalability. Whether you’re setting up an essential LAN connection or advanced IPv6 routing, this guide covers CLI commands, real-world labs, and troubleshooting tips updated for Cisco IOS XE 2024. We can categorize Cisco Interfaces

Physical Interfaces: GigabitEthernet, Serial, FastEthernet, etc.

Logical Interfaces: Loopback, VLAN subinterfaces, Tunnel interfaces.

Virtual Interfaces: Port-channel (EtherChannel) for link aggregation.

In 2025, configuring Cisco router interfaces is vital for supporting 5G backhaul, IoT scalability, and SD-WAN deployments, with 100G, 400G, and emerging 800G interfaces driving AI, high-density networks, and data center interconnects, making this guide essential for CCNA and enterprise engineers.

Step-by-Step Interface Setup

After connecting to a router, you need to get into the Global Configuration Mode of your router using the following commands:

NU_Router>
NU_Router>enable
Password:
NU_Router#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
NU_Router(config)#
NU_Router(config)#

The next option is to choose the correct interface. Many interfaces are available on Cisco routers, such as Ethernet, Fast Ethernet, Gigabit Ethernet, 10G Ethernet, serial interface, Logical and virtual, etc. All interfaces in IOS are exactly numbered. For example, we want to configure Fast Ethernet, which has serial 0/0. We should enter the command as shown below.

NU_Router(config)#interface FastEthernet 0/0

Adding a Description to the Cisco Router Interface

This feature is not necessary, so you may bypass it. It describes the interface but does not assist with the configuration. It just helps prevent human error. For example, add a description (e.g., description 400G to DataCenter or description 800G to AI Cluster) to aid troubleshooting. In 2025, this is key for managing 100G/400G/800G interface documentation.

 NU_Router(config-if)#description <Write description of the interface here>

Setting the IP Address on the Interface

Now that you have done everything necessary to add the IP address to the interface, use the following command to enter an IP address according to your IP scheme.

NU_Router(config-if)#ip address 192.168.100.1 255.255.255.0

Enabling Interface

Before using the router interface, you also need to enable the corresponding interface. We can allow the router interface by entering the following command.

NU_Router(config-if)#no shutdown
%LINK-5-CHANGED: Interface FastEthernet0/0, changed state to up

As of 2025, Cisco IOS XE 17.9 introduces auto-configuration for 100G, 400G, and 800G interfaces on Nexus 9000 and 8000 Series, using QSFP28, QSFP-DD, and OSFP modules, streamlining high-speed lab configurations.

Verifying Cisco Router Interface Configuration

We can verify the interface configuration using several commands. For example, the <show ip interface brief> is the most helpful command for verifying interface configuration. The output of this command displays all interfaces with their IPv4 address and the current status. The configured and connected interfaces should display a status of “up” and Protocol “up”. Any other statements would indicate a problem with the configuration or the cabling. Also, remember that show commands are working in “Privileged mode”

In the same way, we can verify the configuration of the interface using <show running-config>  and also with show startup-config. We can also verify connectivity from the interface using the ping command. The ping command sends five consecutive pings and measures minimal, average, and maximum round-trip times. Exclamation marks in Cisco routers also verify connectivity.

In 2025, use show interfaces status with Cisco DNA Center integration to monitor 100G, 400G, and 800G interfaces in real-time, and show controller optics for detailed diagnostics on 400G/800G coherent optics (e.g., TX/RX power, laser state).

NU_Router#
NU_Router#show ip interface brief
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 192.168.100.1 YES manual up up
FastEthernet0/1 10.10.10.254 YES manual up up
Vlan1 unassigned YES unset administratively down down
NU_Router#

Other commands to verify the Cisco router interface configuration.

  • show interfaces– Displays statistics for all interfaces on the device.
  • Ping – Using the ping command, we can generate five exclamation marks verifying connectivity to the remote side.
  • show running-config-.The command shows the entire configuration of the router.
  • show startup-config:- When the configuration is saved with the write command, we can verify it using the command mentioned.

Configuring Global Parameters – Summary

To configure the global parameters for the Cisco router, follow these steps.

1. configure terminal

2. hostname name

3. enable secret password

4. no ip domain-lookup

DETAILED STEPS

CommandPurpose
Step 1Enter global configuration mode, when using the console port.Enter global configuration mode when using the console port.
Step 2hostname nameExample:
Router(config)# hostname Router		Specifies the name for the router.
Step 3enable secret passwordExample:
Router(config)# enable secret shxabxaA 		Specifies an encrypted password to prevent unauthorized access to the router.
Step 4no ip domain-lookup Example:
Router(config)# no ip domain-lookup		Disables the router from translating unfamiliar words (typos) into IP addresses.

Add IPv6 unicast-routing for IPv6 support, service-policy BRANCH-QOS for 5G/100G/400G/800G traffic prioritization, and enable 400G/800G-specific FEC with zr-optics fec cFEC on supported interfaces.

2025 Interface Configuration Best Practices

In 2025, optimize interfaces with QoS for 5G traffic, enable IPv6 and 100G/400G/800G support using QSFP28/QSFP-DD/OSFP modules, leverage mGig for Wi-Fi 7, and use AI analytics like Cisco ThousandEyes for proactive maintenance on Cisco 8000 Series routers.

Conclusion

This guide equips you with skills to configure Cisco router interfaces, from GigabitEthernet to 100G, 400G, and 800G, preparing you for CCNA labs and enterprise scalability in high-speed networks.

FAQs