Kernel default route is missing for WAN interface.

Products

• VMware VeloCloud SD-WAN

Issue/Introduction

Cusotmer has configured a WAN interface (GE1 for example) but the kernel default route is not installed in the linux routing table for this interface. The VCMP tunnels will be formed normally but the direct traffic will fail to exit from this interface

edge:Test:~# route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
0.0.0.0 10.10.10.10 0.0.0.0 UG 4 0 0 ge2

Cause

The network ip is used as the default gateway ip for the interface which is not allowed by Linux.

 

For example: 

Interface IP: 10.10.10.113/30

GW : 10.10.10.112

Resolution

Two possible solutions are available:

1- Fix the IP address for the interface and default gateway to use host IPs instead of the Network address in case of a /30 subnet.

2- Use /31 subnet as in that case the network address is allowed by linux to be used as the default gateway address.