How Floods Tested Zhengzhou’s Telecom Backbone and What It Reveals About Network Resilience

In recent days, heavy rain in Zhengzhou, Henan, caused unprecedented flooding that led to serious urban waterlogging and significant loss of life and property.

Rescue teams are working intensively on the ground, and many hope the rain will cease soon so that normal life can be restored.

As a telecommunications professional, the author observed not only the disaster’s human impact but also extensive damage to communication network infrastructure.

Historically, large‑scale disasters damage local telecom facilities, yet a reliable network is essential for rescue operations and for stabilizing affected residents.

Consequently, frontline telecom staff must quickly engage in equipment repair and emergency protection work.

Colleagues in Henan have been working overtime to restore services.

The flood’s impact far exceeded typical incidents: core city data centers, including primary and backup rooms, were inundated, a situation not seen in decades.

The most affected equipment were the operators’ HLR (Home Location Register) devices, which store user subscription data and are critical to the core network.

HLR, now called HSS (Home Subscriber Server) in 4G/5G, functions as the user database; failures often lead to major network outages due to data loss or link interruptions.

For example, a 2017 incident in Nanning caused an 8‑hour outage when 800,000 HLR records were mistakenly deleted.

In Zhengzhou, although the HLR flooded and went out of service, disaster‑recovery mechanisms prevented a large‑scale outage.

Residents are advised to keep their phones powered on, as handset registration with the HLR is required for network access.

When HLR is unavailable, phones cannot complete signaling, preventing network authentication.

Operators extended the location‑update interval to avoid registration failures during the crisis.

Additionally, the operators’ out‑of‑province backup HLR was activated, temporarily replacing the damaged local HLR and ensuring service continuity.

This high‑level backup is designed for extreme scenarios such as wars, terrorist attacks, or earthquakes.

In severe cases where signaling load overwhelms the network, operators may temporarily disable user authentication to reduce traffic.

During this flood, the fixed‑line broadband radius equipment went offline, and the solution was to disable authentication, allowing users to connect without credential checks.

Radius (Remote Authentication Dial‑In User Service) is a device that authenticates users; disabling it kept broadband services operational.

Other impacts included brief disruptions to microwave relay links and IPTV services, which were relatively minor.

Telecom engineers continue intensive repairs, and core network functionality is expected to be restored soon as floodwaters recede.

Finally, the author expresses prayers for the end of the rain, the safety of the people, and the success of the frontline engineers.