duplicate host names

[Nancy Stout]

I have been asked to verify our disaster recovery. I have been asked to restore a make_recovery_tape to a different server with the same host name but a different IP address. I was able to complete the make recovery however it took a very long time to go through all of the processes. I could not logon with this new IP address. Then when I took a look at the netconf file the original IP address was there. I changed this to the test IP address and am trying a reboot. Will this even work? Can you have two host names the same with different IP address on the same network?

[Steven E. Protter]

Shalom,

duplicate host names on the two systems is not recommended but possible.

Ignite has a change interface that you can invoke from the console to change the hostname and IP address and many other things such as filesystem size.

You must change the IP address anyway. I would recommend using a different hostname, but it is not a requirement.

SEP

[Nancy Stout]

Steven,

I did change the IP address at ignite time, however it loaded the original IP address. As for the host name the request is to keep it the same so that a restore of the database can be attempted and the database relies on the host name to be brought up. I am still waiting for the system to reboot after manually changing the IP address in netconf.

[Bill Hassell]

hostnames are just for humans -- we don't handle numbers all that well. Ignite will restore the hostname (and IP address) of the original system unless you add customization before taking the Ignite backup. This will cause a big problem with your production system if you connect it to the same network. On another network (isolated from the production network), you can probably work on the new server safely. The long bootup time was very likely cause by NFS which is all messed up with this new clone.

The first thing to do is to take the new server off the network -- no connections at all, as they may cause big database problems for Sybase, Oracle, Informix, etc. with your production server. Then connect your GSP/MP cable (I am assuming you have a fairly new boxes) and setup a unique address. Use the GSP/MP port to access the new server. The command (after logging in to the GSP/MP) is CO (short for CONSOLE). Then edit two files in /etc/rc.config.d:

1. nfsconf -- disable NFS client and server options, especially if you aren't using NFS.

2. netconf -- change the IP address for the primary LAN.

Now edit /etc/hosts and change the host/IP address line. Now if you are using a DNS server, you'll have to disable it until you come up with a plan for DR. The DNS server can override /etc/hosts so you'll need to understand how the two systems will be connected.

Network databases such as Oracle and Sybase can be quite tricky in DR. If the two servers are on the same network, shutting down the database on the DR may cause production to shutdown. This may be avoided by telling the database that the hostname is address 127.0.0.1 -- 127.0.0.1 is always the local machine. Success depends on the database.

[Yogeeraj_1]

hi nancy,

> Can you have two host names the same with different IP address on the same network?

you can implement something *similar* using the DNS. That is two machines with different IP addresses and whenever you want to switchover, you just change the DNS entry. Of course, it may take some time to propagate to all clients on the network.

just some thoughts

kind regards
yogeeraj

[Nancy Stout]

Thank you all for responding. We are planning on testing a different way that will not cause us the problems with DSN.