Aggregating multiple links between physical interfaces creates a single logical point-to-point trunk link or a LAG. The LAG balances traffic across the member links within an Aggregated Ethernet (AE) bundle and effectively increases the uplink bandwidth. An aggregate interface has one or more contributing interfaces as a part of the LAG bundle. These contributing interfaces are also referred to as the child interfaces of the bundle.
In QFX5000 Series devices, the counter for child interface (IFL) statistics is seen to always show a zero value. This article explains why this is so and suggests a configuration that would enable you to view these values.
When you check the statistics of a child interface that is a part of an AE bundle, its IFD statistics counter shows a meaningful number and keeps incrementing as traffic passes. However, in the case of IFL statistics, the counter always remains zero.
Consider ae0 as our AE interface for example.
Physical interface: ae0, Enabled, Physical link is Up Interface index: 640, SNMP ifIndex: 555, Generation: 131 Link-level type: Ethernet, MTU: 1514, Speed: 80Gbps, BPDU Error: None, Ethernet-Switching Error: None, MAC-REWRITE Error: None, Loopback: Disabled, Source filtering: Disabled, Flow control: Disabled, Minimum links needed: 1, Minimum bandwidth needed: 1bps Device flags : Present Running Interface flags: SNMP-Traps Internal: 0x4000 Current address: 40:a6:77:79:23:b0, Hardware address: 40:a6:77:79:23:b0 Last flapped : 2018-09-25 08:20:15 PDT (00:34:51 ago) Statistics last cleared: 2018-09-25 08:54:26 PDT (00:00:40 ago) Traffic statistics: Input bytes : 189506 69760 bps Output bytes : 181856 69752 bps Input packets: 1762 84 pps Output packets: 1762 84 pps IPv6 transit statistics: Input bytes : 0 Output bytes : 0 Input packets: 0 Output packets: 0 Input errors: Errors: 0, Drops: 0, Framing errors: 0, Runts: 0, Giants: 0, Bucket drops: 0, Policed discards: 0, Resource errors: 0 Output errors: Carrier transitions: 0, Errors: 0, Drops: 0, MTU errors: 0, Resource errors: 0, Bucket drops: 0 Egress queues: 12 supported, 5 in use Queue counters: Queued packets Transmitted packets Dropped packets 0 0 1755 0 3 0 0 0 4 0 0 0 7 0 82 0 8 0 0 0 Queue number: Mapped forwarding classes 0 best-effort 3 fcoe 4 no-loss 7 network-control 8 mcast Logical interface ae0.0 (Index 550) (SNMP ifIndex 562) (HW Token 4095) (Generation 135) Flags: Up SNMP-Traps 0x4004000 Encapsulation: ENET2 Statistics Packets pps Bytes bps Bundle: Input : 1835 84 189250 69328 Output: 1835 84 189570 69400 Adaptive Statistics: Adaptive Adjusts: 0 Adaptive Scans : 0 Adaptive Updates: 0 Link: et-0/0/12.0 Input : 0 0 0 0 >>> Counter always remains "0." Output: 0 0 0 0 et-0/0/13.0 Input : 0 0 0 0 >>> Counter always remains "0." Output: 0 0 0 0
The reason for this is that the total traffic passing through both the child interfaces is calculated and displayed as a consolidated figure in the ae0.0 interface statistics.
This behavior is the default, and is seen only on QFX5000 Series devices.
Output from an MX device indicates that these values are displayed:
Logical interface ae0.0 (Index 332) (SNMP ifIndex 121) (Generation 144) Flags: Up SNMP-Traps 0x4004000 Encapsulation: ENET2 Statistics Packets pps Bytes bps Bundle: Input : 424793370780835 345 326940686814466282 431328 Output: 334670669199897 6 292287761500557636 14976 Adaptive Statistics: Adaptive Adjusts: 0 Adaptive Scans : 0 Adaptive Updates: 0 Link: et-2/0/0.0 Input : 10591186717743 112 7388762352396915 121544 Output: 7847248056539 0 6559665293353807 528 et-2/0/1.0 Input : 7727667633427 116 5399926341471831 134304 Output: 5701970984450 3 4735849431666002 7224
If you would like to view the IFL statistics for each child interface that is a part of an AE bundle. you can use the hidden knob child-stats-enable to your existing configuration:
child-stats-enable
set interfaces ae0 aggregated-ether-options child-stats-enable
Note
The hidden knob does not auto-populate on pressing the Tab key or the Space bar. You will have to type the command completely.
The above feature can be applied only on devices that run Junos OS releases 18.1R3-S3 and 19.X (and later).
After you have enabled the above knob, you can verify the statistics on each child interface (ifl).
Logical interface ae0.0 (Index 550) (SNMP ifIndex 562) (HW Token 4095) (Generation 135) Flags: Up SNMP-Traps 0x4004000 Encapsulation: ENET2 Statistics Packets pps Bytes bps Bundle: Input : 1972 84 202704 69984 Output: 1972 82 202944 68280 Adaptive Statistics: Adaptive Adjusts: 0 Adaptive Scans : 0 Adaptive Updates: 0 Link: et-0/0/12.0 Input : 1881 83 198456 68768 Output: 1883 82 192872 67672 et-0/0/13.0 Input : 30 1 3840 1216 Output: 31 0 3968 608