On-Premises Appliances: Resolving Dual Gateway Misconfigurations on Multi-NIC CSGs

Table of Contents

• Symptoms
• Affected Environments
• Root Cause
• Confirming the Misconfiguration
• Resolution Steps
• Related Articles

Symptoms

A CSG using two Network Interface Cards (NICs) may unexpectedly appear offline or become unreachable from external subnets. If the CSG is connected to an XCM, its status will display as Disconnected.

These symptoms typically appear immediately after the CSG is updated, rebooted, or after a network configuration change.

Affected Environments

• Platform: Hardware (1U server, DIN Rail)
• Component: CSG

Root Cause

This issue occurs when a default gateway is assigned to both the Trusted and Untrusted interfaces on the CSG.

During a reboot or network service restart, the CSG must choose a default routing path. If two gateways are configured, the system will select one at random. If it selects the unexpected or strictly internal gateway, traffic attempting to reach the CSG from outside its immediate subnet will not route back correctly.

Confirming the Misconfiguration

Before making changes, confirm the presence of dual gateways using either the Web UI or the Setup Console.

Via the Web UI (if accessible)

1. Navigate to Settings > Network.
2. Scroll to the Network Routes section.
3. Check for routes with the destination 0.0.0.0.

If two distinct routes are listed for 0.0.0.0, a dual gateway misconfiguration is confirmed.

Via the Setup Console

1. Access the CSG through SSH or a physical keyboard and monitor.
2. Navigate to Network Tools > Show Network.
3. Review the routes listed at the bottom of the output.

If two routes are listed for 0.0.0.0, the issue is confirmed.

Resolution Steps

Warning: Changing the gateway configuration will alter the system's routing paths. You may experience an unexpected network disconnection from your current session while performing these resolution steps as the new routes are applied.

To resolve this issue, configure the CSG to use only a single default route. This change must be made through the CSG Setup Console.

1. Access the CSG Setup Console through SSH or a physical terminal.
2. Navigate to Network Configuration.
3. Review both Configure Trusted and Configure Untrusted to determine how IP addresses are assigned.
4. Apply the fix that matches your environment.

Scenario A: Both Interfaces Use Static IPs (Manual)

• Identifier: Both interfaces have the Gateway field manually populated.
• Fix: Edit the connection profile for the interface that should not serve as the primary route, then remove the IP address from the Gateway field.

Scenario B: Both Interfaces Use DHCP (Automatic)

• Identifier: Both interfaces have IPv4 Configuration set to Automatic. In this case, the DHCP server is likely assigning a gateway lease to both NICs.
• Fix: Edit the connection profile for the interface that should not serve as the primary route, go to the Routing section, and select Never use this network for default route.

Scenario C: Mixed Configuration (One Static, One DHCP)

• Identifier: One interface has a statically assigned gateway, while the other is set to Automatic.
• Fix: Determine which interface should handle default traffic:
  • If the static interface should handle default traffic, edit the Automatic interface and select Never use this network for default route.
  • If the Automatic interface should handle default traffic, remove the manual gateway entry from the static interface.

Once the changes are saved, the network service will restart and apply the correct single routing path.