This article explains why the value for IPv6 transit statistics on interfaces under the IPv6 family always shows a counter zero.
Under every logical interface (IFL), the transit statistics output is the total output of IPv4 count and IPv6 count. This comes as a consolidated output for both. For a given IFL, since both IPv6 and IPv4 traffic use the same defined VLANs, the output display does not show separate transit statistics for IPv4 and IPv6 flows. The total sum output is displayed under IPv4 count and the count for IPv6 is displayed as "0".
Example:
Verify the statistics on a logical interface (ifl)
user@host> show interfaces xe-0/0/2.0 extensive
Logical interface xe-0/0/2.0 (Index 555) (SNMP ifIndex 521) (HW Token 4095) (Generation 140) <-- IFL index is 555 and SNMP index is 521
Flags: Up SNMP-Traps 0x4004000 Encapsulation: ENET2
Traffic statistics: <-- IPv4 + IPv4 statistics
Input bytes : 47047879516
Output bytes : 96186352494
Input packets: 672015933
Output packets: 1297185918
IPv6 transit statistics: <-- IPv6 transit statistics is always displayed as 0. The counter never increments.
Input bytes : 0
Output bytes : 0
Input packets: 0
Output packets: 0
Local statistics:
Input bytes : 47047879516
Output bytes : 43762402410
Input packets: 672015785
Output packets: 625170851
Transit statistics: <-- IPv4 + IPv6 statistics
Input bytes : 0 640544 bps
Output bytes : 52423950084 675168 bps
Input packets: 148 1082 pps
Output packets: 672015067 1082 pps
IPv6 transit statistics: <-- IPv6 statistics is always displayed as 0. The counter never increments.
Input bytes : 0
Output bytes : 0
Input packets: 0
Output packets: 0
When such behavior is seen on QFX5k series devices and EX4600 devices, this does not mean the device does not pass through IPv6 traffic. IPv6 transit traffic count is included in the consolidated output. This is expected behavior and not an issue with transit traffic.
Verify the statistics for SNMP index:
The output above shows the SNMP ifIndex is 521.
user@host> show interfaces xe-0/0/2.0 extensive
Logical interface xe-0/0/2.0 (Index 555) (SNMP ifIndex 521) (HW Token 4095) (Generation 140)
{master:0}
user@host> show snmp mib get jnxIpv6IfInOctets.521
jnxIpv6IfInOctets.521 = 0
Similarly, if you fetch SNMP iflIndex from all logical interfaces that have IPv6 traffic on it, you can see the below:
user@root> show snmp mib walk jnxIpv6IfStatsTable
jnxIpv6IfInOctets.509 = 0
jnxIpv6IfInOctets.521 = 0
jnxIpv6IfOutOctets.519 = 0
jnxIpv6IfOutOctets.511 = 0
NOTE: The above output can be used to verify all interfaces that are assigned IPv6 addresses and are running fine although the statistics count is 0.
This behavior is seen only in the above-listed products. Below is an example from PTX5000 device:
user@host> show interfaces et-0/0/6 extensive
Physical interface: et-0/0/6, Enabled, Physical link is Up
Interface index: 347, SNMP ifIndex: 531, Generation: 350
Link-level type: Ethernet, MTU: 1514, Speed: 40Gbps, BPDU Error: None, Loop Detect PDU Error: None, Loopback: Disabled, Source filtering: Disabled, Flow control: Enabled
Device flags : Present Running
Interface flags: SNMP-Traps Internal: 0x4000
Link flags : None
CoS queues : 8 supported, 8 maximum usable queues
Hold-times : Up 0 ms, Down 0 ms
Damping : half-life: 0 sec, max-suppress: 0 sec, reuse: 0, suppress: 0, state: unsuppressed
Current address: 30:b6:4f:02:29:06, Hardware address: 30:b6:4f:02:29:06
Last flapped : 2017-02-15 21:40:06 PST (22:55:13 ago)
Statistics last cleared: 2017-02-16 20:33:02 PST (00:02:17 ago)
Traffic statistics:
Input bytes : 1760000 0 bps
Output bytes : 1540000 0 bps
Input packets: 16000 0 pps
Output packets: 14000 0 pps
IPv6 transit statistics:
Input bytes : 880000
Output bytes : 770000
Input packets: 8000
Output packets: 7000