Static RoutingCCNA 200-301

IPv6 Static Route Not Working — Missing ipv6 unicast-routing

Presenting Symptom

IPv6 static routes are configured but traffic to the destination network fails; ping to the next-hop or remote network returns 'Destination unreachable' or no reply.

Network Context

A small branch office with a Cisco 4321 ISR running IOS XE 16.9 connects to a central HQ via a single WAN link. The branch router has a directly connected IPv6 prefix (2001:db8:1::/64) on GigabitEthernet0/0/0 and a static route for the HQ network (2001:db8:2::/64) pointing to the next-hop 2001:db8:1::2. The engineer can ping the next-hop but not the remote network.

Diagnostic Steps

Check IPv6 routing table for the static route

show ipv6 route static

IPv6 Routing Table - default - 3 entries
Codes: C - Connected, L - Local, S - Static
S   2001:db8:2::/64 [1/0]
     via 2001:db8:1::2, GigabitEthernet0/0/0

If the static route is present, the route is configured. If missing, the route is not configured or has an error. If present but not active (e.g., no 'S' code), the next-hop may be unreachable.

Verify IPv6 connectivity to the next-hop address

ping ipv6 2001:db8:1::2

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2001:db8:1::2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms

If ping succeeds, the next-hop is reachable. If it fails, there is a Layer 2 or Layer 3 issue on the link. In this scenario, ping succeeds, so the next-hop is reachable.

Check if IPv6 unicast routing is enabled globally

show running-config | include ipv6 unicast-routing

No output (the command returns nothing if not configured)

If the command returns no output, IPv6 unicast routing is disabled. This is the root cause: without 'ipv6 unicast-routing', the router will not forward IPv6 packets even if routes are present. Normal output would be 'ipv6 unicast-routing'.

Confirm IPv6 forwarding is disabled

show ipv6 interface brief

GigabitEthernet0/0/0   [up/up]
    FE80::1
    2001:db8:1::1
    [administratively down]

If IPv6 unicast-routing is disabled, interfaces may show 'administratively down' for IPv6 or no IPv6 address. However, the interface may still show up/up but IPv6 packets will not be forwarded. This step confirms the symptom.

Root Cause

The global configuration command 'ipv6 unicast-routing' is missing. By default, IPv6 unicast routing is disabled on Cisco IOS routers. Without this command, the router will not forward IPv6 packets between interfaces, even if static routes are configured. The router can ping its own interfaces and directly connected neighbors, but traffic to remote networks is dropped.

Resolution

Enable IPv6 unicast routing globally: Router(config)# ipv6 unicast-routing This command enables IPv6 packet forwarding. No other changes are needed. The static route already exists and will become active immediately.

Verification

1. Verify IPv6 routing is enabled: show running-config | include ipv6 unicast-routing Output: ipv6 unicast-routing 2. Verify the static route is now active: show ipv6 route static Output: S 2001:db8:2::/64 [1/0] via 2001:db8:1::2, GigabitEthernet0/0/0 3. Test connectivity to the remote network: ping ipv6 2001:db8:2::1 Output: !!!!! (success)

Prevention

1. Always include 'ipv6 unicast-routing' in the base configuration template for any router that will route IPv6 traffic. 2. Use configuration management tools (e.g., Ansible, Chef) to enforce that IPv6 unicast routing is enabled on all routers. 3. During initial device setup, verify IPv6 routing is enabled before configuring static routes or dynamic routing protocols.

CCNA Exam Relevance

On the CCNA 200-301 exam, this scenario appears in troubleshooting questions where IPv6 static routes are configured but not working. The exam may present a show command output and ask why the route is not in the routing table or why traffic fails. The key fact is that 'ipv6 unicast-routing' must be enabled globally for IPv6 forwarding. Without it, the router acts as an IPv6 host and will not forward packets.

Exam Tips

Memorize that 'ipv6 unicast-routing' is required for IPv6 routing; it is disabled by default.

When troubleshooting IPv6 connectivity, always check the routing table first, then verify the global configuration for 'ipv6 unicast-routing'.

Remember that 'show ipv6 route' will show connected and local routes even without unicast routing enabled, but static routes will not be active.

Commands Used in This Scenario

show ipv6 route

Displays the IPv6 routing table on a Cisco router, showing all known IPv6 routes and their next-hop information for troubleshooting and verification of IPv6 routing.

show running-config

Displays the current active configuration in DRAM, showing all non-default settings.

Test Your CCNA Knowledge

Practice with scenario-based questions to prepare for the CCNA 200-301 exam.

Practice CCNA Questions