TP-Link ER605 Load Balancer Not Automatically Switching from Airtel WAN to Jio Backup Connection – Complete Troubleshooting and Configuration Guide

Internet connectivity has become a critical requirement for businesses, offices, educational institutions, and service providers. To ensure uninterrupted connectivity, organizations often deploy multi-WAN routers such as the TP-Link Omada ER605 Gigabit Multi-WAN VPN Router. The ER605 supports load balancing and automatic failover between multiple Internet Service Providers (ISPs), providing redundancy and high availability.

A common issue reported by network administrators is that the ER605 does not automatically switch from the primary ISP connection (Airtel) to the backup ISP connection (Jio) when the Airtel internet service fails. However, when the Airtel router is completely powered off, the ER605 successfully shifts traffic to the Jio connection.

This article explains the causes of this issue, how WAN failover works, and the recommended configuration for reliable internet redundancy.

Network Environment

Example Deployment:

• Router: TP-Link Omada ER605 v2
• Firmware: 2.0.1 Build 20220223 Rel.68551
• Primary ISP: Airtel Broadband (WAN1)
• Secondary ISP: Jio Fiber (WAN/LAN2 or WAN3)
• Failover Mode: Link Backup
• Objective: Automatic internet failover without user intervention

Understanding the Problem

Observed Behavior

Scenario	Result
Airtel internet fails but router remains powered ON	No automatic failover
Airtel router powered OFF	Failover to Jio works
Jio remains active and healthy	Working normally

This behavior indicates that the router detects physical link failures but may not properly detect internet connectivity failures.

How WAN Failover Works

The ER605 determines WAN health using multiple methods:

Physical Link Detection

The router checks:

• Ethernet cable status
• WAN port link state
• Router/modem availability

If the Airtel modem remains powered on, the WAN port remains active.

Internet Connectivity Detection

The router checks:

• Reachability of public IP addresses
• DNS server accessibility
• Internet availability

Only when internet monitoring is correctly configured can the router distinguish between:

• Internet available
• Internet unavailable but modem powered ON

Root Cause Analysis

Cause 1: Physical Link Remains Active

When Airtel service fails but the modem remains powered on:

• WAN Ethernet link remains active
• Router sees WAN as connected
• No failover occurs

Cause 2: Improper Online Detection

Default Online Detection settings may not adequately verify real internet connectivity.

Cause 3: Outdated Firmware

Firmware version:

2.0.1 Build 20220223

is an early release and lacks several failover improvements added in later versions.

Cause 4: Incorrect Detection Targets

Monitoring ISP gateway addresses instead of public internet servers may produce false-positive results.

Cause 5: Session Persistence

Existing NAT sessions may remain tied to WAN1 even after WAN status changes.

Recommended Online Detection Configuration

Navigate to:

Transmission → Load Balancing → Online Detection

Configure WAN1:

Parameter	Value
Mode	Manual
Ping	8.8.8.8
DNS Lookup	1.1.1.1

Configure WAN2/WAN3:

Parameter	Value
Mode	Manual
Ping	8.8.4.4
DNS Lookup	1.0.0.1

These public DNS servers provide reliable internet reachability testing.

Recommended Link Backup Configuration

Navigate to:

Transmission → Load Balancing → Link Backup

Settings:

Primary Connection

• WAN1 (Airtel)

Backup Connection

• WAN/LAN2 or WAN3 (Jio)

Link Backup

• Enabled

Failover Mode

• Automatic

Recovery

• Automatic

This ensures internet traffic automatically shifts to Jio when Airtel fails.

Load Balancing vs Link Backup

Load Balancing

Traffic is distributed between multiple ISPs simultaneously.

Advantages:

• Better bandwidth utilization
• Higher throughput

Disadvantages:

• Sessions may use different WAN links
• More complex troubleshooting

Link Backup

One ISP remains active while another remains standby.

Advantages:

• Simpler management
• Faster failover
• Predictable routing

Recommended for most business offices.

DNS Recommendations

Use public DNS servers:

Primary DNS:
8.8.8.8

Secondary DNS:
1.1.1.1

Avoid ISP-provided DNS servers whenever possible.

Proper Failover Testing Procedure

Incorrect Test:

Powering OFF the Airtel router.

This only tests physical link detection.

Correct Test:

1. Keep Airtel router powered ON.
2. Disconnect Airtel fiber input.
3. Wait 30–60 seconds.
4. Monitor WAN status.

Expected Result:

• WAN1 changes to Offline.
• Jio becomes Active.
• Internet remains available.

Diagnostic Commands

Continuous Ping Test

ping 8.8.8.8 -t

Observe packet loss during failover.

Route Verification

tracert 8.8.8.8

Confirm traffic is routed through Jio after failover.

Public IP Verification

nslookup myip.opendns.com resolver1.opendns.com

Verify that public IP changes from Airtel to Jio.

Firmware Upgrade Recommendation

The installed firmware version is significantly outdated.

Benefits of upgrading:

• Improved WAN detection
• Better failover performance
• Enhanced VPN stability
• Security updates
• Bug fixes

Always:

1. Backup configuration.
2. Download correct firmware.
3. Upgrade firmware.
4. Reboot router.
5. Verify failover operation.

Best Practices

• Use Link Backup instead of Load Balancing for redundancy.
• Monitor public IP addresses.
• Configure multiple health-check targets.
• Update firmware regularly.
• Test failover quarterly.
• Maintain ISP diversity.
• Document WAN configurations.
• Monitor router logs.
• Use quality CAT6 cabling.
• Backup router configuration files.

Conclusion

When a TP-Link ER605 automatically switches to Jio only after the Airtel router is powered off, the issue is typically related to WAN health detection rather than failover functionality itself. The router continues to see the Airtel connection as active because the modem remains online, even though internet access may be unavailable.

Proper Online Detection settings, Link Backup configuration, public DNS monitoring, and firmware updates significantly improve automatic failover reliability. Implementing these recommendations ensures uninterrupted internet connectivity and minimizes business downtime during ISP outages.