Cloned from launchpad bug 1520775. Description: I found this one when build up a test env. Steps to reproduce: 1) I create a set of external network, internal network and router. The external network has gateway ip in its subnet. 2) connect the external, internal network and router, by using router-gateway-set, router-interface-add. 3) Then I realize my physical network doesn't have a gateway. So I update the subnet of external network with --no-gateway. 4) I can't see the default route be deleted in router namespace, even if I restart l3-agent. I try it in legacy router and DVR, they both have this problem, and I believe HA router will have this problem. Specification URL (additional information): https://bugs.launchpad.net/neutron/+bug/1520775
https://code.engineering.redhat.com/gerrit/112357
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHBA-2017:2663