A widely used API is failing intermittently due to the hostname resolution. There is a requirement to update the DNS server to point to a different address. After making the DNS server change in the /etc/resolv.conf and rebooting the gateway nodes, the IP address is reverting back to the old DNS server.
API Gateway 9.X
DNS settings involve two files: /etc/resolv.conf and /etc/dhcp/dhclient.conf. In the /etc/dhcp/dhclient.conf, there is a supercede statement that still had the old DNS server IP address.
For each node, update the DNS server IP address in the /etc/resolv.conf and /etc/dhcp/dhclient.conf
(1) Make a backup copy: cp /etc/dhcp/dhclient.conf /etc/dhcp/dhclient.conf.bkup
(2) Edit the file and update the IP address: vi /etc/dhcp/dhclient.conf
(3) Save the file: wq!
(4) Make a backup copy: cp /etc/resolv.conf /etc/resolv.conf.bkup
(5) Edit the file and update the IP address: vi /etc/resolv.conf
(6) Save the file: wq!
(7) Reboot the node
(8) Confirm the IP address change has stayed: cat /etc/resolv.conf, cat /etc/dhcp/dhclient.conf