nmcli does not accept 0.0.0.0/0 for the default gateway in ipv4.gateway

Environment

• Red Hat Enterprise Linux 7

Issue

• I need to modify the default gateway via nmcli but I receive error about invalid gateway address.

Resolution

• The nmcli utility does not support using 0.0.0.0/0 for the default gateway in ipv4.gateway.
• To work around this problem, you may create separate routes for both the 0.0.0.0/1 and 128.0.0.0/1 subnets, which covers also the full IPv4 address space.

Root Cause

• The nmcli utility does not support using 0.0.0.0/0 for the default gateway in ipv4.gateway.

Diagnostic Steps

# nmcli con modify ens3 ipv4.gateway 192.168.11.1
Error: Failed to modify connection 'ens3': ipv4.gateway: gateway cannot be set if there are no addresses configured

# nmcli con modify ens3 ipv4.gateway "0.0.0.0/0 192.168.11.1"
Error: failed to modify ipv4.gateway: invalid gateway address '0.0.0.0/0 192.168.11.1'.

# nmcli con modify ens3 +ipv4.routes "0.0.0.0/1 192.168.11.1, 128.0.0.0/1 192.168.11.1"
# nmcli dev reapply ens3
Connection successfully reapplied to device 'ens3'.

# ip route
0.0.0.0/1 via 192.168.11.1 dev ens3 proto static metric 100 
128.0.0.0/1 via 192.168.11.1 dev ens3 proto static metric 100 
192.168.11.0/24 dev ens3 proto kernel scope link src 192.168.11.179 metric 100 

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