Networking. Failover an IP address.

[mark vosberg]

Networking question failing over another servers ip. Verify my procedure please? Just wanted to bounce it off some of the hpux guru's

I have two hpux 11.11 servers.
I am failing over an application from one server to another server. I need to temporarily reuse its IP. Plus several external systems connect to the application and expect connections to come from the old IP. I plan to use ifconfig and route cmd.

primary server IP = 15.43.9.164 Need to reuse this ip.
failover server main IP=15.43.10.20. Has 2 nic cards one is unused.

# First assign 15.43.9.164 to the 2nd unused nic card. The primary server is down and disconnected from the network.
Root> ifconfig lan2 inet 15.43.9.164 netmask 255.255.255.0

# Now set the static routes for the two external systems to force all network traffic to them use lan2 even if one of them is directly connected to the primary IP address.
Root> route add host 15.43.10.35 15.43.9.1 1
Root> route add host 15.43.13.11 15.43.9.1 1

Will this do the trick? Now the failover server is reusing the old ip and all traffice to the external systems looks like it is still coming from the old ip.

Thanx for info.

[Matti_Kurkela · Accepted solution]

Command syntax looks good.

The netmask seems to suggest that the primary server and the failover server might be on separate IP network segments.

The important question is, where does the cable connected to lan2 go? If it's connected to the same network segment as the primary server, that's good.

If it's connected to the same segment as your failover server's main interface, not so good: the incoming packets would not find your lan2 interface unless the upstream router(s) were configured to direct the traffic to your failed-over IP in a special way.

You might want to let the people who manage your network router(s) verify your plan. They should know the network topology, which is absolutely necessary to know for verifying plans like this.

If your network has firewalls, notify the firewall administrators too: depending on firewall configuration, there might be some adjustments they need to do.

[mark vosberg]

Thanx for the response matti. I did this once 6 years ago but I lost my notes. Since both servers are in production I cannot afford a mistake.

Yes lan2 is connected to the same subnet as the primary server. I am assuming ifconfig sends a gratuitous ARP when I setup lan2. Anyway thanx for the response. I think I will close this one out.

[mark vosberg]

See above comments.