Courseiva
RoutingPrivileged EXEC

show ipv6 interface brief

Quick overview of which interfaces have IPv6 configured and whether they are operational.

Definition: show ipv6 interface brief is a Cisco IOS privileged exec command. Displays a summary of all interfaces with IPv6 addresses, their operational status (up/up), and all IPv6 addresses assigned including link-local, global unicast, and anycast addresses.

Overview

The 'show ipv6 interface brief' command is a fundamental tool in the Cisco IOS toolkit for any network engineer working with IPv6. It provides a concise, one-line-per-interface summary of IPv6 status and addresses, allowing rapid verification of IPv6 configuration and operational state across all interfaces on a device. This command is essential for CCNA and CCNP candidates because it directly addresses the need to quickly assess whether IPv6 is enabled, which interfaces have IPv6 addresses, and whether those interfaces are up or down.

Unlike the more verbose 'show ipv6 interface' command, which displays detailed per-interface information including neighbor discovery, ICMPv6, and routing protocol specifics, 'show ipv6 interface brief' strips away the noise and presents only the most critical data: interface name, status (up/down), protocol status, and the IPv6 addresses assigned. This makes it the go-to command for initial IPv6 deployment verification, troubleshooting connectivity issues, and auditing configurations. In a typical workflow, a network engineer might first use 'show ipv6 interface brief' to get a high-level view, then drill down with 'show ipv6 interface [interface]' for deeper analysis.

The command fits into broader troubleshooting by helping isolate whether an issue is at Layer 1/2 (interface status) or Layer 3 (address assignment). For example, if an interface shows 'up/up' but no IPv6 address, the problem is likely in the IPv6 configuration; if the interface shows 'down/down', the issue is physical or data link. Important IOS behavior to note: the command does not alter the running configuration and requires no special privilege level beyond privileged EXEC (enable mode).

Output is typically not buffered, meaning it displays immediately and is not stored for later retrieval. This command is available in all IOS versions that support IPv6, including IOS 12.x, 15.x, and 16.x, with consistent syntax. For CCNA and CCNP candidates, mastering this command is crucial for efficient IPv6 management and exam success, as it frequently appears in simulation and troubleshooting questions.

Syntax·Privileged EXEC
show ipv6 interface brief [interface-id]

When to Use This Command

  • Confirm IPv6 addresses are assigned after configuring ipv6 address
  • Verify link-local addresses are auto-generated on IPv6-enabled interfaces
  • Check interface status for IPv6 connectivity troubleshooting
  • Identify all IPv6 addresses on a device including EUI-64 generated addresses

Command Examples

IPv6 interface brief output

Router# show ipv6 interface brief
GigabitEthernet0/0         [up/up]
    FE80::C8B3:73FF:FEA2:1234
    2001:DB8:1::1
GigabitEthernet0/1         [up/up]
    FE80::C8B3:73FF:FEA2:1235
    2001:DB8:2::1
Loopback0                  [up/up]
    FE80::1
    2001:DB8:100::1

Understanding the Output

Each interface shows: status [line/protocol], link-local address (FE80::/10 — auto-generated from MAC or configured), and any global unicast addresses configured. Link-local addresses are always present on IPv6-enabled interfaces even if not explicitly configured. FE80:: addresses use EUI-64 by default (MAC-based).

Configuration Scenarios

Verify IPv6 addressing on a router after initial configuration

A network engineer has configured IPv6 addresses on multiple interfaces of a router and needs to quickly confirm that all addresses are correctly assigned and interfaces are operational.

Topology

R1(Gi0/0)---2001:db8:1:1::/64---(Gi0/0)R2 R1(Gi0/1)---2001:db8:1:2::/64---(Gi0/1)R3

Steps

  1. 1.Step 1: Enter privileged EXEC mode: Router> enable
  2. 2.Step 2: Run the command: Router# show ipv6 interface brief
  3. 3.Step 3: Review the output to ensure each interface shows 'up/up' and has the expected IPv6 address.
Configuration
! Configuration on R1
interface GigabitEthernet0/0
 ipv6 address 2001:db8:1:1::1/64
!
interface GigabitEthernet0/1
 ipv6 address 2001:db8:1:2::1/64

Verify: Router# show ipv6 interface brief GigabitEthernet0/0 [up/up] FE80::1 2001:db8:1:1::1 GigabitEthernet0/1 [up/up] FE80::2 2001:db8:1:2::1

Watch out: Forgetting to enable IPv6 globally with 'ipv6 unicast-routing' will cause the command to show no IPv6 addresses even if configured on interfaces.

Troubleshoot a down IPv6 interface

A remote site reports that IPv6 connectivity is lost. The engineer needs to determine if the issue is at the interface level or configuration level.

Topology

R1(Gi0/0)---2001:db8:2:1::/64---(Gi0/0)R2

Steps

  1. 1.Step 1: Enter privileged EXEC mode: Router> enable
  2. 2.Step 2: Run the command: Router# show ipv6 interface brief
  3. 3.Step 3: Observe that GigabitEthernet0/0 shows 'down/down' indicating a Layer 1/2 issue.
  4. 4.Step 4: Check physical cabling and interface configuration.
Configuration
! Configuration on R1
interface GigabitEthernet0/0
 ipv6 address 2001:db8:2:1::1/64
 no shutdown

Verify: Router# show ipv6 interface brief GigabitEthernet0/0 [down/down] FE80::1 2001:db8:2:1::1 Expected healthy output: [up/up]

Watch out: An interface can show 'up/down' if IPv6 is not enabled on the interface (e.g., missing 'ipv6 enable' or 'ipv6 address' command).

Troubleshooting with This Command

When troubleshooting IPv6 connectivity issues, 'show ipv6 interface brief' is often the first command to run. A healthy output shows each interface with a status of [up/up] and at least one IPv6 address (link-local and possibly global). The key fields to focus on are the interface status (first field) and protocol status (second field).

If the status shows [down/down], the interface is physically or data-link down; check cables, line protocol, and interface configuration (e.g., 'shutdown' vs 'no shutdown'). If it shows [up/down], IPv6 is not enabled on the interface; verify that 'ipv6 enable' or an 'ipv6 address' command is configured. If the interface is [up/up] but no IPv6 address appears, the interface may have IPv6 enabled but no address assigned (e.g., only link-local via 'ipv6 enable').

Common symptoms this command helps diagnose include: missing IPv6 addresses (configuration omission), interface down (physical issue), or duplicate address detection failure (though this requires deeper inspection with 'show ipv6 interface'). A step-by-step diagnostic flow: 1) Run 'show ipv6 interface brief' to get an overview. 2) If an interface is down, check physical connectivity and interface status with 'show interfaces'. 3) If an interface is up but has no IPv6 address, check IPv6 configuration with 'show running-config interface [interface]'. 4) If an interface has an address but connectivity fails, use 'ping ipv6' and 'traceroute ipv6' to isolate further. Correlate this command's output with 'show ipv6 route' to verify routing, and 'show ipv6 neighbors' to check neighbor discovery.

For example, if an interface shows [up/up] with an IPv6 address but you cannot ping the next-hop, the issue may be in routing or neighbor discovery. The command is also useful for verifying that IPv6 is globally enabled; if no interfaces appear at all, ensure 'ipv6 unicast-routing' is configured. In summary, 'show ipv6 interface brief' is a powerful first-line troubleshooting tool that quickly narrows down the scope of IPv6 problems.

CCNA Exam Tips

1.

CCNA exam: every IPv6-enabled interface has a link-local address (FE80::/10)

2.

Link-local addresses are not routable beyond the local segment

3.

Global unicast addresses (2000::/3) are the publicly routable equivalent of IPv4 public addresses

4.

EUI-64 format inserts FFFE in the middle of the MAC and flips the 7th bit

5.

Required to enable IPv6 routing: ipv6 unicast-routing in global config

Common Mistakes

Forgetting to enable ipv6 unicast-routing globally — routers do not forward IPv6 packets without it

Confusing link-local (FE80::/10) with unique-local (FC00::/7) — link-local is per-interface only, unique-local is roughly equivalent to RFC 1918 private space

Not enabling ipv6 address on interfaces before routing works

show ipv6 interface brief vs show ip interface brief

These commands are often confused because both provide a quick interface overview, but one focuses on IPv6 addressing while the other shows IPv4. Understanding their differences is crucial for accurate network diagnostics.

Aspectshow ipv6 interface briefshow ip interface brief
Protocol familyIPv6 onlyIPv4 only
Address displayAll IPv6 addresses (link-local, global unicast, anycast)Primary IPv4 address or 'unassigned'
Status informationInterface status (up/down) for IPv6Interface status and line protocol status
Typical useVerifying IPv6 connectivity and addressingQuick device health overview
Output formatPer-interface list with multiple addressesCompact one-line summary per interface
CategoryRoutingDiagnostics

Use show ipv6 interface brief when you need to quickly check IPv6 address assignments and interface operational status for IPv6.

Use show ip interface brief when you want a fast overview of all interfaces and their IPv4 addressing and line protocol state.

Platform Notes

In IOS-XE (e.g., Catalyst 9000 switches), the 'show ipv6 interface brief' command syntax and output are identical to classic IOS. However, on some IOS-XE platforms, the command may also display VLAN interfaces (SVI) and port-channel interfaces. On NX-OS (Nexus switches), the equivalent command is 'show ipv6 interface brief' as well, but the output format differs slightly: it includes a 'Vlan' column and uses a different status notation (e.g., 'protocol-up/link-up' instead of [up/up]).

For example, on NX-OS: 'show ipv6 interface brief' might output 'Ethernet1/1 -- 2001:db8::1/64'. On ASA firewalls, there is no direct equivalent; instead, use 'show ipv6 interface' or 'show interface ip brief' (which shows IPv4 only). For IOS-XR, the command is 'show ipv6 interface brief' and is available, but the output is more detailed and includes interface state and line protocol state separately.

In older IOS versions (12.x), the command may not show link-local addresses in the brief output, while 15.x and later include them. Always ensure IPv6 is globally enabled with 'ipv6 unicast-routing' for the command to display addresses. There are no privilege level differences; the command is available at privilege level 1 (user EXEC) but typically used at level 15 (privileged EXEC).

Related Commands

show interfaces

Displays detailed Layer 1 and Layer 2 statistics for all interfaces or a specific interface: line protocol state, hardware type, MAC address, MTU, bandwidth, duplex, speed, input/output rates, error counters, and queue statistics.

show ip interface brief

Displays a one-line summary of all interfaces showing the IP address assigned, operational status (up/down), and line protocol status. The fastest way to get a device health overview.

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