Many offices today use two internet connections to ensure continuous connectivity and better speed. A load balancer such as the TP-Link TL-ER605 VPN Router allows both internet lines to work together and provides automatic failover if one connection stops working.
However, when offices try to integrate a load balancer into an existing network, they often face problems like:
Internet not working with static IP configuration
Remote users unable to connect to servers
RDP or ERP access failing
IP conflicts between routers
This article explains why these issues occur and how to properly design a dual-internet network for offices using servers like Tally or ERP systems.
In many offices, only one internet router is used at a time.
Example setup:
Internet Router
LAN IP: 192.168.50.1
Office Network: 192.168.50.x
Server: 192.168.50.10
All computers in the office connect to the router and receive IP addresses from the same LAN network.
When a second internet connection is installed, companies often configure both routers with the same LAN IP and network range, so the office computers do not need reconfiguration.
Example:
Router 1 LAN: 192.168.50.1
Router 2 LAN: 192.168.50.1
While this works when only one router is active, it becomes a serious problem when a load balancer is introduced.
When a load balancer is installed, both routers connect simultaneously to the load balancer's WAN ports.
Example:
Internet 1 → Router 1 → Load Balancer WAN1
Internet 2 → Router 2 → Load Balancer WAN2
If both routers have the same LAN IP, the load balancer cannot properly determine which gateway to use.
This causes:
Routing conflicts
NAT issues
Port forwarding failures
Remote Desktop (RDP) connection failures
ERP or Tally access interruptions
Essentially, the network becomes confused because two devices are claiming the same internal gateway address.
The correct approach is to let the load balancer become the main router for the office network.
Example structure:
Internet 1
│
ISP Router 1
LAN: 192.168.10.1
│
WAN1
Load Balancer
WAN2
│
ISP Router 2
LAN: 192.168.30.1
│Load Balancer LAN
192.168.50.1Office Network
192.168.50.x
In this setup:
The load balancer manages the office network
Both internet routers are used only as internet gateways
Each router has a different LAN IP range
Example configuration:
LAN IP: 192.168.10.1
Connected to: Load Balancer WAN1
LAN IP: 192.168.30.1
Connected to: Load Balancer WAN2
LAN IP: 192.168.50.1
Office Network Range: 192.168.50.x
IP Address: 192.168.50.10
All office computers continue using the 192.168.50.x network, so no workstation changes are required.
If your office provides remote access to software such as accounting or ERP systems, proper routing becomes even more important.
Remote access systems often use:
Remote Desktop (RDP)
Application publishing tools
VPN connections
When using dual internet connections, the server should always communicate through a specific WAN connection.
This is configured using policy routing in the load balancer.
Example rule:
Source IP: 192.168.50.10 (Server)
Outgoing WAN: WAN1 only
This ensures incoming and outgoing traffic use the same internet connection, preventing connection drops.
To allow remote users to connect to the server, port forwarding must be configured.
Example:
External Port: 3389
Internal IP: 192.168.50.10
Protocol: TCP
Interface: WAN1
Remote users connect using the public IP address of WAN1.
Exposing RDP directly to the internet is risky.
Many cyber attacks target open RDP servers.
A better approach is to use VPN access first.
The TP-Link TL-ER605 VPN Router supports several VPN types including:
OpenVPN
IPsec VPN
L2TP VPN
Recommended process:
Remote User → VPN Connection → Office Network → Server Access
Once connected to VPN, users can open RDP using the local server IP.
When configured correctly, a load balancer provides several advantages:
If one ISP fails, the second connection automatically takes over.
Traffic from multiple users is distributed across both internet lines.
Critical systems like accounting software remain accessible.
VPN connections protect the server from direct internet exposure.
Two routers should never use the same LAN IP when connected to a load balancer.
The load balancer should control the office LAN network.
Each internet router must use a different LAN IP range.
Servers requiring remote access should be bound to a specific WAN connection.
VPN should be used instead of exposing RDP directly to the internet.
Following these best practices ensures a stable, secure, and scalable office network capable of supporting modern business applications.
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