HP 1920 loopback problems on trunks between switches

[Dunky]

I have a number of HP 1920 switches.

The interconnects between the switches are configured with the following:

loopback-detection enable

loopback-detection control enable

loopback-detection per-vlan enable

Every so often I am getting the following in my syslog server which are both log entries and SNMP traps...
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/RECOVERED(t) Trap 1.3.6.1.4.1.25506.2.95.1.0.4: Loopback on the interface 18972672 GigabitEthernet1/0/25 in VLAN 1 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/RECOVERED(t) Trap 1.3.6.1.4.1.25506.2.95.1.0.4: Loopback on the interface 18972672 GigabitEthernet1/0/25 in VLAN 2 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/RECOVERED(t) Trap 1.3.6.1.4.1.25506.2.95.1.0.4: Loopback on the interface 18972672 GigabitEthernet1/0/25 in VLAN 5 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/RECOVERED(t) Trap 1.3.6.1.4.1.25506.2.95.1.0.4: Loopback on the interface 18972672 GigabitEthernet1/0/25 in VLAN 3 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/RECOVERED(t) Trap 1.3.6.1.4.1.25506.2.95.1.0.4: Loopback on the interface 18972672 GigabitEthernet1/0/25 in VLAN 51 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/RECOVERED(t) Trap 1.3.6.1.4.1.25506.2.95.1.0.4: Loopback on the interface 18972672 GigabitEthernet1/0/25 in VLAN 56 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/RECOVERED(t) Trap 1.3.6.1.4.1.25506.2.95.1.0.4: Loopback on the interface 18972672 GigabitEthernet1/0/25 in VLAN 55 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/RECOVERED(t) Trap 1.3.6.1.4.1.25506.2.95.1.0.4: Loopback on the interface 18972672 GigabitEthernet1/0/25 in VLAN 53 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/RECOVERED(t) Trap 1.3.6.1.4.1.25506.2.95.1.0.4: Loopback on the interface 18972672 GigabitEthernet1/0/25 in VLAN 52 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/RECOVERED(t) Trap 1.3.6.1.4.1.25506.2.95.1.0.4: Loopback on the interface 18972672 GigabitEthernet1/0/25 in VLAN 4 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/RECOVERED(t) Trap 1.3.6.1.4.1.25506.2.95.1.0.4: Loopback on the interface 18972672 GigabitEthernet1/0/25 in VLAN 59 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/RECOVERED(t) Trap 1.3.6.1.4.1.25506.2.95.1.0.4: Loopback on the interface 18972672 GigabitEthernet1/0/25 in VLAN 58 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/RECOVERED(t) Trap 1.3.6.1.4.1.25506.2.95.1.0.4: Loopback on the interface 18972672 GigabitEthernet1/0/25 in VLAN 64 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/RECOVERED(t) Trap 1.3.6.1.4.1.25506.2.95.1.0.4: Loopback on the interface 18972672 GigabitEthernet1/0/25 in VLAN 200 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/RECOVERED(t) Trap 1.3.6.1.4.1.25506.2.95.1.0.4: Loopback on the interface 18972672 GigabitEthernet1/0/25 in VLAN 65 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/RECOVERED(t) Trap 1.3.6.1.4.1.25506.2.95.1.0.4: Loopback on the interface 18972672 GigabitEthernet1/0/25 in VLAN 57 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/LPDETECT_RECOVERED(l): Loopback on GigabitEthernet1/0/25 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/LPDETECT_RECOVERED(l): Loopback on GigabitEthernet1/0/25 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/LPDETECT_RECOVERED(l): Loopback on GigabitEthernet1/0/25 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/LPDETECT_RECOVERED(l): Loopback on GigabitEthernet1/0/25 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/LPDETECT_RECOVERED(l): Loopback on GigabitEthernet1/0/25 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/LPDETECT_RECOVERED(l): Loopback on GigabitEthernet1/0/25 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/LPDETECT_RECOVERED(l): Loopback on GigabitEthernet1/0/25 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/LPDETECT_RECOVERED(l): Loopback on GigabitEthernet1/0/25 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/LPDETECT_RECOVERED(l): Loopback on GigabitEthernet1/0/25 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/LPDETECT_RECOVERED(l): Loopback on GigabitEthernet1/0/25 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/LPDETECT_RECOVERED(l): Loopback on GigabitEthernet1/0/25 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/LPDETECT_RECOVERED(l): Loopback on GigabitEthernet1/0/25 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/LPDETECT_RECOVERED(l): Loopback on GigabitEthernet1/0/25 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/LPDETECT_RECOVERED(l): Loopback on GigabitEthernet1/0/25 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/LPDETECT_RECOVERED(l): Loopback on GigabitEthernet1/0/25 recovered.
Aug 1 10:01:52 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/LPDETECT_RECOVERED(l): Loopback on GigabitEthernet1/0/25 recovered.
Aug 1 10:01:53 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/RECOVERED(t) Trap 1.3.6.1.4.1.25506.2.95.1.0.4: Loopback on the interface 18976768 GigabitEthernet1/0/26 in VLAN 51 recovered.
Aug 1 10:01:53 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/RECOVERED(t) Trap 1.3.6.1.4.1.25506.2.95.1.0.4: Loopback on the interface 18976768 GigabitEthernet1/0/26 in VLAN 3 recovered.
Aug 1 10:01:53 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/RECOVERED(t) Trap 1.3.6.1.4.1.25506.2.95.1.0.4: Loopback on the interface 18976768 GigabitEthernet1/0/26 in VLAN 52 recovered.
Aug 1 10:01:53 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/RECOVERED(t) Trap 1.3.6.1.4.1.25506.2.95.1.0.4: Loopback on the interface 18976768 GigabitEthernet1/0/26 in VLAN 56 recovered.
Aug 1 10:01:53 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/RECOVERED(t) Trap 1.3.6.1.4.1.25506.2.95.1.0.4: Loopback on the interface 18976768 GigabitEthernet1/0/26 in VLAN 55 recovered.
Aug 1 10:01:53 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/RECOVERED(t) Trap 1.3.6.1.4.1.25506.2.95.1.0.4: Loopback on the interface 18976768 GigabitEthernet1/0/26 in VLAN 2 recovered.
Aug 1 10:01:53 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/RECOVERED(t) Trap 1.3.6.1.4.1.25506.2.95.1.0.4: Loopback on the interface 18976768 GigabitEthernet1/0/26 in VLAN 53 recovered.
Aug 1 10:01:53 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/RECOVERED(t) Trap 1.3.6.1.4.1.25506.2.95.1.0.4: Loopback on the interface 18976768 GigabitEthernet1/0/26 in VLAN 4 recovered.
Aug 1 10:01:53 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/RECOVERED(t) Trap 1.3.6.1.4.1.25506.2.95.1.0.4: Loopback on the interface 18976768 GigabitEthernet1/0/26 in VLAN 1 recovered.
Aug 1 10:01:53 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/RECOVERED(t) Trap 1.3.6.1.4.1.25506.2.95.1.0.4: Loopback on the interface 18976768 GigabitEthernet1/0/26 in VLAN 5 recovered.
Aug 1 10:01:53 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/RECOVERED(t) Trap 1.3.6.1.4.1.25506.2.95.1.0.4: Loopback on the interface 18976768 GigabitEthernet1/0/26 in VLAN 63 recovered.
Aug 1 10:01:53 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/RECOVERED(t) Trap 1.3.6.1.4.1.25506.2.95.1.0.4: Loopback on the interface 18976768 GigabitEthernet1/0/26 in VLAN 64 recovered.
Aug 1 10:01:53 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/RECOVERED(t) Trap 1.3.6.1.4.1.25506.2.95.1.0.4: Loopback on the interface 18976768 GigabitEthernet1/0/26 in VLAN 57 recovered.
Aug 1 10:01:53 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/LPDETECT_RECOVERED(l): Loopback on GigabitEthernet1/0/26 recovered.
Aug 1 10:01:53 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/LPDETECT_RECOVERED(l): Loopback on GigabitEthernet1/0/26 recovered.
Aug 1 10:01:53 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/LPDETECT_RECOVERED(l): Loopback on GigabitEthernet1/0/26 recovered.
Aug 1 10:01:53 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/LPDETECT_RECOVERED(l): Loopback on GigabitEthernet1/0/26 recovered.
Aug 1 10:01:53 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/LPDETECT_RECOVERED(l): Loopback on GigabitEthernet1/0/26 recovered.
Aug 1 10:01:53 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/LPDETECT_RECOVERED(l): Loopback on GigabitEthernet1/0/26 recovered.
Aug 1 10:01:53 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/LPDETECT_RECOVERED(l): Loopback on GigabitEthernet1/0/26 recovered.
Aug 1 10:01:53 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/LPDETECT_RECOVERED(l): Loopback on GigabitEthernet1/0/26 recovered.
Aug 1 10:01:53 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/LPDETECT_RECOVERED(l): Loopback on GigabitEthernet1/0/26 recovered.
Aug 1 10:01:53 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/LPDETECT_RECOVERED(l): Loopback on GigabitEthernet1/0/26 recovered.
Aug 1 10:01:53 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/LPDETECT_RECOVERED(l): Loopback on GigabitEthernet1/0/26 recovered.
Aug 1 10:01:53 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/LPDETECT_RECOVERED(l): Loopback on GigabitEthernet1/0/26 recovered.
Aug 1 10:01:53 192.168.100.9 2016 local7 notice SWITCH-05 %%10LPDETECT/5/LPDETECT_RECOVERED(l): Loopback on GigabitEthernet1/0/26 recovered.

It is effectivly a fully meshed LAN with two ports on each switch being connetected to other switches. MSTP is all configured and working ok but we get these errors on different switches every 7-10 days and when it occurs in office hours it causes issues.

Dos anyone know what would cause these and if there is a way of preventing users losing connectivity?
Thanks

Steve

[parnassus]

Hi!

Those (LPDETECT_RECOVERED and LPDT_RECOVERED) are Comware 5 notification messages (both with Severity Level: 5 which groups notification messages for a "Normal but significant condition") related to LPDETECT (Loop Detect for Loop Condition Handling) and LPDT (Loopback Detection) modules; they state that "Loopback on the interface is eliminated" or "The loop condition on an interface was removed" (for the LPDETECT_RECOVERED) and "The loop condition on a port was removed" (for the LPDT_RECOVERED) on related interfaces/ports.

Are you referring to the scenario described on this post?

[Dunky]

Hi parnassus,

Yes that is the LAN which I have the issue on.

From what I can tell trawling thru logs, is that MSTP changed BAGG2 on SWITCH-02 to FORWDING because no BPDU's were seen on BAGG2 n SWITCH-03.  Immediatly after this I see the LPDETECT_BLOCK & LPDETECT_RECOVERED messages.

I have no idea why SWITCH-03 didnt receive BDPU's from SWITCH-00, but I think this is the cause ot the LPDETECT-BLOCK.

I am beginning to wonder whether maybe I should have loopback detection enabled on uplinks and just rely on MSTP?

[parnassus]

Probably, are your wondering to enable Loopback Detection globally on each "edge" unit (Switch 04, 05 and 06, right?) and then set Loopback Detection and Detection Control on trunk/hybrid interfaces (maybe with Detection in VLAN too)?

The more I look at your network map the more I think you've replicated a sort of "IRF Core (in a sort of ring topology with all those BAGGs that loop back to Switch 00) with a sort of (distributed?) Trunking between the Core and Edge Switches" scenario...but this was done using HPE 1920!

A real challenge!

[Dunky]

Hi,

Yes you are correct in that I have enabled Loopback Detection globally (but on EVERY switch).

I have "loopback-detection enable" on all interfaces.

In addtion, on the trunk ports, I have "loopback-detection control enable" and "loopback-detection per-vlan enable".

The LAN is in and working fine apart from these LPDETECT_BLOCK & LPDETECT_RECOVER errors which have an impact. I have VLAN's split across the fibre uplinks with failiver and its working a treat :)

In fact I have just discovered that I have "stp loop-protection" on g1/0/26 on both SWITCH-05 & -06.  Have just removed that as they were the only two with it and the only two that exhibit the problem (so far as I can tell by looking at logs which only go back a week or so). Will see if that makes any difference although I am not too hopeful.

Looking at the logs I have come up with the following sequence of events:

09.59.38 SWITCH-03  BAGG2 Instance 0,1,2 No BDPU received

10.00.09 SWITCH-02 BAGG2 Inst 0,1,2 detected topology change

                                     BAGG2 is set to FORWARDING Inst 0,1,2

10.00.10 SWITCH-01 BAGG2 Inst 0 detected toopolgy change

10.00.12 SWITCH-04 Int g1/025 Inst 0 detected topology change

10.00.14 SWITCH-00 BAGG1 Inst 0 detected topology change 

10.00.12 SWITCH-05 Int g1/0/25 Inst 0 Topology Change

                                    LPDETECT_BLOCK on g1/0/25 and g1/0/26 (fibres)

10.00.27 SWITCH-02 Inst 0,1,2 BAGG2 set to discard

10.01.52 SWITCH-05 LPDETECT_RECOVERED on g1/0/25 and g1/0/26

[16again · Accepted solution]

Do not enable loopdetect on links between switches!   Use it only on access ports.
On a loop, some interface will have to enter block mode. (by design)
If inter-switch port is in the loop, loopdetection might kick in on that link, taking down ALL traffic.   Loop detection should only take down the access link causing the loop.

[Dunky]

Thanks for the reply 16again.

At present I have:

loopback-detection enable

 loopback-detection control enable

 loopback-detection per-vlan enable

on the inter-switch links, and just "loopback-detection enable" on the access links.

I will disable loopback-detection on the interswitch links. 

On ports where clients are connected via phones (thus trunk ports), would you just enable loop detection or have the three commands above that I currently have on the interswitch links?

Another query if I may, what does the "stp loop-protection" command do and do I need it anywhere?  I thought the whole purpose of STP was to prevent loops, so not quite seeing the relevance of this command.

TIA

[Dunky]

fyi, I have not seen any further issues sincxe disabling loopback-detection on the interswitch links.