IHQ constant packets in incoming queue

[Chrizhitz]

Good morning

I am facing the following problem on a customer location with main and backup router. cisco ISR4331/K9

We see constant incoming IHQ packets on the WAN Interfaces on both routers. At the same time there is almost no traffic on the WAN Interface Gi0/0/2 on the standby router. 

we lost TACACS connection to the main router and "fixed" it by increasing the hold-que in to 2000 pakets. I do not see any other irregularities like high cpu load or massive packet counts.

has anyone encountered the same problem or can tell me in which direction I have to investigate.

sh interface summary (see attached doc)

thanks in advance

Chris

[Joseph W. Doherty]

If the count remains the same and occasionally increases, remaining the same, basically behaving like a "high water mark", that may be a bug as I believe it's supposed to show the current ingress queue depth, not the highest seen to date.

[Chrizhitz]

after 5 hours 56 minutes no new IHQ packets.

IHQ (if working normal) always shows the current situation on the ingress queue with every refresh.

If there are 0 the IHQ shows 0 and so on.

I agree it behaves like a bug but then how come we lost TACACS access when Ingress queue exceeded approx. 300 packets and we where able to fix it by increasing the hold-queue in? 

[Joseph W. Doherty]

The possible bug would have been the IHQ never showing lower values than prior values.  If that's not happening, I misunderstood what you described as happening.

As to having IHQ non-zero values. even if usages appears low, much can happen in milliseconds that won't be seen in longer term averages.

Generically, if unfamiliar, look up "microburstimg".