Courseiva
IPv6Privileged EXEC

show ipv6 traffic

Shows IPv6 and ICMPv6 traffic counters to help diagnose IPv6 connectivity and NDP issues.

Syntax·Privileged EXEC
show ipv6 traffic

When to Use This Command

  • Troubleshooting NDP (Neighbor Discovery Protocol) failures.
  • Verifying Router Advertisement (RA) messages are being sent.
  • Diagnosing IPv6 forwarding issues with packet counters.
  • Checking for IPv6 errors like no route, bad headers, or redirects.

Command Examples

Show IPv6 traffic counters

R1# show ipv6 traffic
IPv6 statistics:
  Rcvd: 12543 total, 0 local destination
        0 source-routed, 0 truncated
        0 format errors, 0 hop count exceeded
        0 bad header, 0 unknown option, 0 bad source
        0 unknown protocol, 0 not a router
  Sent: 11890 total, 0 forwarded
        0 fragmented into 0 fragments, 0 failed
        0 encapsulation failed, 0 no route, 0 too big
ICMPv6 statistics:
  Rcvd: 234 input, 0 checksum errors, 0 too short
        0 redirects, 60 unreachable, 0 echo, 0 echo reply
        42 ND router solicitation, 0 ND router advert
        80 ND neighbor solicitation, 52 ND neighbor advert
        0 ND redirect, 0 group query, 0 group report, 0 MLDv2
  Sent: 188 output, 0 rate-limited
        0 redirects, 0 unreachable, 0 echo, 0 echo reply
        6 ND router solicitation, 38 ND router advert
        72 ND neighbor solicitation, 72 ND neighbor advert
        0 ND redirect

ICMPv6 counters show NDP activity: 38 Router Advertisements sent (expected on an RA-enabled interface), 72 Neighbor Solicitations (NDP ARP equivalent) sent and received. Zero errors indicates healthy IPv6 forwarding.

Understanding the Output

Key ICMPv6 counters: Router Solicitation (RS) = clients requesting RA; Router Advertisement (RA) = router sending /64 prefix and M/O flags; Neighbor Solicitation (NS) = equivalent to ARP request; Neighbor Advertisement (NA) = ARP reply equivalent. If NS/NA counts are zero, NDP is broken. If 'no route' counter is incrementing, routing is missing. Use 'clear ipv6 traffic' to reset counters before testing.

CCNA Exam Tips

1.

CCNA exam tip: ICMPv6 does the work that ICMP + ARP + IGMP do in IPv4 — it covers ping, neighbor discovery, router discovery, and multicast listener.

2.

CCNA exam tip: If NS/NA counts are zero on an active interface, NDP may be blocked by an ACL.

3.

CCNA exam tip: Growing 'hop count exceeded' counters usually indicate a routing loop.

4.

CCNA exam tip: This command is the IPv6 equivalent of 'show ip traffic' for IPv4 statistics.

Common Mistakes

Mistake 1: Blocking ICMPv6 entirely with an ACL and then wondering why IPv6 is broken — NDP uses ICMPv6 types 133-137.

Mistake 2: Ignoring the 'no route' counter when troubleshooting — incrementing value = missing route.

Mistake 3: Forgetting to use 'clear ipv6 traffic' before testing — old counters make test results ambiguous.

Related Commands

ping ipv6 [address]

Sends ICMPv6 echo requests to an IPv6 destination to test connectivity. Functionally equivalent to 'ping [ip]' for IPv4 but uses ICMPv6 instead of ICMP.

show ipv6 neighbors

Displays the IPv6 neighbor discovery cache, showing the mapping of IPv6 addresses to MAC addresses on directly connected links, used to verify neighbor reachability and troubleshoot IPv6 connectivity.

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.

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