hub with multiple tunnel hops is being removed / unstable connection

Products

• DX Unified Infrastructure Management (Nimsoft / UIM)

Issue/Introduction

A hub in your environment is several "hops" away from the primary hub, across several layers of tunnels.

This hub is disappearing or turning red in IM on a random basis even though the tunnel seems to be connected.

One or more of the hubs that the traffic passes through shows the following message in the hub.log:

  hub: hubinfo_check - /(Domain)/(Hub)/(robotname)/hub has been inactive for 1800 seconds and will be removed

The hub is not inactive, so why is this message occuring?

 

Environment

DX UIM - 23.4.6 or prior
Hub - 23.4.6 or prior
Multiple "layers" of tunnels (e.g. primary hub-->tunnel to 2nd hub--->tunnel to 3rd hub--->tunnel to 4th hub--->tunnel to 5th hub)

Cause

partially caused by defect, partially caused by number of tiers

Resolution

The hub 23.4.6 and prior has a known issue where the hub "status" may not be properly communicated through multiple tiers of hubs, causing higher-tier hubs to think that lower-tier hubs have gone inactive.

This will be resolved in DX UIM 23.4.7/hub 23.4.7 (CU7) due in early March 2026.

However, due to limitations inherent to the architecture of UIM hub tunnels, it is likely that some instability will still be experienced when the number of tiers is increased.  The fix in CU7 will only improve the situation, it is unlikely to correct it entirely.

The ideal number of tiers for a DX UIM hub environment is three (3) tiers:

Primary hub--->Tunnel Server--->Tunnel Clients

With each additional "tier" (where tunnel clients also behave as tunnel servers to additional clients) there is a chance to increase the instability, which will cause hubs to occasionally turn red or disappear in Infrastructure Manager and return without user intervention within 10-60 minutes.

This is a known limitation of the product design.  Where possible, reduce the number of hub tiers to improve the performance.

Generally, four (4) tiers has been observed to be relatively stable, but five (5) or more tiers will introduce greater instability.