Overcoming IP Conflicts on Huawei B525 LTE Router in a Busy Office

Introduction

In a bustling office environment, every device that connects to the network can influence performance, security, and reliability. When a Huawei B525 LTE router is deployed to share a single broadband connection, it must juggle multiple IP addresses, NAT translations, and DHCP leases. Even a well‑managed router can run into IP conflicts when the office expands, new devices join, or when configuration mistakes are made.

An IP conflict occurs when two or more devices attempt to use the same IP address simultaneously. The result is intermittent connectivity, dropped sessions, and frustration for staff who rely on a stable internet connection for email, cloud services, and collaboration tools.

This article explains the causes of IP conflicts on the Huawei B525, provides detailed troubleshooting steps, and offers preventive measures to keep a busy office’s network running smoothly.

Understanding IP Conflicts

IP addresses in a local network are usually distributed by a DHCP server. The router allocates addresses from a defined range and tracks which addresses are in use. When the range is exhausted or misconfigured, two devices may receive the same address.

On a LAN, an IP conflict generates ARP packets that reveal duplicate MAC addresses for the same IP. Devices will repeatedly attempt to resolve the address and will experience packet loss. The symptoms can be subtle—slow file transfers, intermittent VPN connections, or a single workstation that appears offline.

Why the Huawei B525 Can Trigger Conflicts

The Huawei B525 is a popular small‑form router because it offers LTE, Ethernet, and Wi‑Fi in a compact package. However, its firmware is primarily designed for home or small office use. In a busy office, a few factors can strain its DHCP and NAT capabilities:

• Limited DHCP pool – The default pool may be too small for dozens of devices.
• Static IP mismanagement – A static IP that falls within the DHCP range can clash with a dynamic lease.
• Multiple interfaces – The router can run both 4G and wired connections; mis‑routing between them can duplicate addresses.
• Firmware limitations – Some older firmware versions have bugs that incorrectly release leases, causing reuse of addresses while other devices still hold them.
• Simultaneous VPN or PPPoE sessions – When VPN tunnels are established, additional virtual IPs may be allocated on the same subnet, risking overlap.

Common Symptoms to Watch For

By noting these indicators, network managers can focus their diagnosis on the B525’s configuration.

Diagnostic Tools and Techniques

Checking the DHCP Table

Log into the B525 web interface (http://192.168.8.1) and navigate to the DHCP section.
The table lists all current leases, MAC addresses, and assigned IPs. Look for duplicate entries.

Using ARP Inspection

On a Windows workstation, open a terminal and run arp -a.
Cross‑reference the IP list with the MAC addresses in the B525’s DHCP table.
If the same IP maps to two distinct MAC addresses, an IP conflict is present.

Packet Capture with Wireshark

Capture traffic on a workstation’s Ethernet interface.
Filter on arp and look for multiple ARP responses for the same IP.
The presence of who-has and is-at packets for the same IP indicates a conflict.

Router Log Analysis

Under System Log in the B525 interface, search for entries like “IP conflict detected.”
If the router logs report conflicts, it will also indicate the conflicting IP and the two MAC addresses involved.

Step‑by‑Step Solutions

1. Expand or Re‑define the DHCP Pool

Navigate to the DHCP settings.
Increase the starting and ending IP addresses to create a larger pool.
Ensure the new range does not overlap with any reserved static IPs.

Tip: Keep the pool size modest but sufficient—e.g., 192.168.8.100 – 192.168.8.199 for a 100‑device office.

2. Reserve Static IPs Outside the DHCP Range

Assign static IPs to servers, printers, and network devices that require fixed addresses.
Place these assignments outside the DHCP pool, for example, 192.168.8.10 – 192.168.8.20.

3. Disable the DHCP Server on Secondary Interfaces

If the B525 is connected to another router or switch that also runs a DHCP server, disable one to avoid double leasing.
Prefer the B525 to handle DHCP for all LAN devices, or use a dedicated DHCP server on a separate subnet.

4. Adjust DHCP Lease Time

Shorten the lease time (e.g., 12 hours) to reduce the chance of lingering leases after a device disconnects.
Short leases ensure that stale entries are refreshed more quickly.

5. Update Firmware to the Latest Version

Manufacturers frequently patch DHCP bugs in firmware releases.
Check Huawei’s support site for the newest image, then upload it via the router’s System Update page.
Reboot the router after the update.

6. Perform a Factory Reset After Re‑configuration

If conflicts persist, a clean start can help.
Back up the current configuration (under System > Backup).
Execute a factory reset, then restore the backup.
Re‑apply settings with care, ensuring no overlap between static and dynamic ranges.

7. Enable DHCP Address Reservation

The B525 allows binding specific IPs to MAC addresses.
Reserve the IP address for a device by adding its MAC to the reservation list.
This guarantees that the device will always receive the same IP and eliminates accidental duplication.

8. Set Up VLAN Segmentation

Create separate VLANs for Wi‑Fi, wired, and guest networks.
Assign distinct subnets to each VLAN, e.g.,

VLANs isolate DHCP scopes, preventing cross‑conflict between segments.

9. Configure Static Routing for VPN Traffic

If the office uses a VPN over the B525, set static routes to prevent VPN virtual interfaces from sharing the LAN subnet.
Assign a different subnet for VPN endpoints, such as 10.0.0.0/24, and route it through the VPN gateway.

10. Turn on IP Address Conflict Detection (If Available)

Some router firmware offers an option to detect conflicts automatically.
If present, enable it; the router will send notifications when two devices request the same address.

Advanced Troubleshooting

Packet Capture and Analysis

Beyond ARP storms, check for duplicate DHCP offers or acknowledgments.
In Wireshark, filter on bootp.
If two offers for the same IP are seen within seconds, it indicates a conflict.

Inspect Router Logs for “Duplicate Address” Entries

Use SSH to connect to the router (ssh admin@192.168.8.1) and tail /var/log/messages.
Search for “duplicate address” or “conflict” strings.
These logs often point to the specific device and the conflicting address.

Adjust Firewall Rules

Misconfigured firewall rules can cause devices to receive incorrect default gateways, leading to address reuse.
Ensure that all LAN traffic is allowed to pass through the NAT without being redirected to an external interface that may assign its own IP.

Quality of Service (QoS) Configuration

Heavy traffic can fill the NAT table.
Configure QoS to prioritize critical traffic (e.g., VoIP, VPN) and limit excessive connections from non‑essential devices.
This reduces the chance that the router will run out of available NAT slots and start re‑assigning addresses.

Practical Setup Example: A Busy Office

Consider an office with 40 employees, 5 printers, and a VoIP system.
The B525 is connected via its 4G port to a backup LTE connection, while the primary wired connection goes through a switch.

Step 1 – Define Subnets

192.168.1.0/24 – Wired office (LAN)
192.168.2.0/24 – Wi‑Fi office
10.0.0.0/24 – VPN endpoints

Step 2 – Configure DHCP Pools

• LAN pool: 192.168.1.100 – 192.168.1.200
• Wi‑Fi pool: 192.168.2.100 – 192.168.2.200

Reserve static IPs:

• Printer A – 192.168.1.10
• Printer B – 192.168.1.11
• VoIP gateway – 192.168.1.20

Step 3 – Enable VLANs

• VLAN10 – LAN – 192.168.1.0/24
• VLAN20 – Wi‑Fi – 192.168.2.0/24
• VLAN30 – Guest – 192.168.3.0/24

Assign the switch ports to the correct VLANs.

Step 4 – Update Firmware

Download the latest firmware, upload, reboot, and verify the new version in the system information panel.

Step 5 – Monitor for Conflicts

• Use the router’s built‑in log viewer to check for conflict alerts.
• On a workstation, run arp -a daily to spot duplicates.

If an IP conflict surfaces, note the MAC addresses involved, update the DHCP reservation, and adjust the static IP if necessary.

Tips for Prevention

• Keep DHCP pools separate from static IP ranges.
• Update firmware whenever an OTA patch is available.
• Use DHCP lease reservations for critical devices.
• Segment traffic using VLANs to isolate DHCP scopes.
• Educate staff on not manually assigning IPs that fall within the DHCP range.
• Regularly audit the DHCP table and router logs.
• Maintain a change log for any network configuration updates.

FAQ

Q: Why does my office keep experiencing IP conflicts after a firmware update?
A: Some updates modify the DHCP lease algorithm. Verify that the pool still excludes static IPs and that reserved addresses remain outside the dynamic range.

Q: Can I use the B525 as a VPN server?
A: Yes, but assign a dedicated subnet for VPN clients to avoid overlapping with the LAN subnet.

Q: My printer is offline due to an IP conflict. How to fix quickly?
A: Manually set a static IP for the printer outside the DHCP range, then restart the printer and the router.

Q: Is it safe to increase the DHCP pool indefinitely?
A: Expanding the pool can mask underlying issues, but it does not solve the root cause of address reuse. Ensure that the pool size aligns with actual device counts.

Conclusion

In a busy office, the Huawei B525 LTE router is a valuable bridge between cellular redundancy and wired reliability. Yet, its limited DHCP scope and firmware quirks can lead to frustrating IP conflicts. By understanding the root causes, leveraging diagnostic tools, and applying a systematic set of corrective actions—from expanding the DHCP pool to implementing VLAN segmentation—network administrators can eliminate conflicts and maintain seamless connectivity for all office devices.

Continuous monitoring, firmware updates, and disciplined IP management create a resilient environment where every employee can rely on a stable, secure network.