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Virtual IP question

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Marco A.
Esteemed Contributor

Virtual IP question

Hi Guys,

I would like to know if you have an idea on how to do the following.

Basically, I have 2 11.11s, but I would like them to run the same application (just access), I would like to add some redundancy having any kind of "active/passive" IP address.

Is that possible with virtual IP? keep one "on-hold" while the other one is running.

btw - both are connected to the same switch, same vlan.

Best regards,

Just unplug and plug in again ....
5 REPLIES
Taurian
Valued Contributor
Solution

Re: Virtual IP question


Hi Marco,

Sure you can do that, but there are lots of things to consider. Of course with HP Serviceguard, all of this can be automated.

You can easily move your virtual IP from one node to the other. The issue is with the application data.

Is your application data on a shared storage? If not, then keeping updated copy of the data on both nodes might be bit of a pain.

If it is on shared storage then also you have things to consider, like VG activation/deactivation, FS unmounting/mounting, IP relocation, etc, etc.

You can experiment with all of that. Or you can make your life easier by asking your company to invest in HP Serviceguard.

Hope that helps,

Regards,
Taurian.
Jose Mosquera
Honored Contributor

Re: Virtual IP question

Hi Marco,

As Taurian said, you must have a lot of considerations, and ServiceGuard is a solid and reliable product that helps you, of course you need some bucks to install it.

>>Is that possible with virtual IP? keep one "on-hold" while the other one is running.<<

Basically the concept is simple, you must have in each node (active and passive) an IP base, IP-based it must belong to the same network. Now is when it appears the concept of floating IP, as its name implies is to be moved between nodes when a fault occurs. This floating IP is the key, all your connections users must go against this IP.

Please supose this scenario:
nodeA/>ifconfig lan0
lan0: flags=843
inet 10.8.8.100 netmask ffffff00 broadcast 10.8.8.255


nodeB/>ifconfig lan0
lan0: flags=843
inet 10.8.8.101 netmask ffffff00 broadcast 10.8.8.255

Then you define a floating IP (Key) 10.8.8.102

This floating IP overlap on the base IP of the suitable node, you must first be in "nodeA" for this run:
nodeA/>ifconfig lan0:1 10.8.8.102

At this point you already get connectivity to the "node" through the floating IP (10.8.8.102). This assignment is volatile, if the node goes down the floating IP go away too. To retrieve the connection to the node "NodeB" should run the same command above:
nodeB/>ifconfig lan0:1 10.8.8.102

To manually deallocate a node floating IP:
nodeA/>ifconfig lan0:1 0

>>btw - both are connected to the same switch, same vlan.<<

You should design with your communications staff a redundancy strategy to ensure the access to hosts through various network elements.

Rgds.
Marco A.
Esteemed Contributor

Re: Virtual IP question

Thanks Jose,

It is what I am looking for.

Basically this non-critical service is connecting to a DB, and this should be up and running maybe ... all the time, so I was thinking in something cheap and easy, and this seems to be the solution.

Look.

SERVER1 (active) ----+
|-----SWITCH(vid100)
SERVER2 (passive)----+

So I will be pinging the main server from the server2, if I don't receive response from that server I will deallocate the ip from the server1 and allocate it in the server2 with an script.

Marco

Just unplug and plug in again ....
Mel Burslan
Honored Contributor

Re: Virtual IP question

what you are trying to do is the poor man's serviceguard.

I have not done this myself but there is a linux distribution called Freesco (as in resemblance to words Free Cisco) and as far as I know, it is capable of performing basic router functions. All you are asking is configuring a simple redirector. It should not be a problem, provided you have one interface (or two if you have) for the outgoing connections and one for the incoming connection. Should be pretty cheap intel/amd x86 server that can best serve your purpose.

Of course if you want to reinvent the wheel and write a set of scripts which cros checks ping connectivity on each server and redirect incoming packets from one server to the other, you sure can do that but then the question is, do you have that much spare time to devote to it ? If it is a production application, you can not tolerate a sloppy job scripting, which fails often. Good (opposite of sloppy) scripts are hard to come by and and even harder to author.

My 2 cents.
________________________________
UNIX because I majored in cryptology...
Viktor Balogh
Honored Contributor

Re: Virtual IP question

> If it is a production application, you can not tolerate a sloppy job scripting, which fails often.

Not to mention the responsibility of the script writer for this whole thing to work. If you ask me, I would stick to Serviceguard as that way my ass would be covered by a support from a vendor.
****
Unix operates with beer.