host redundancy, how ?

[dalmada]

Hi,

I'm have two web servers on the same network, one acting as a backup to the other.How should I configure the router (2611XM) to redirect the packets to the backup web server if the primary one fails?

thanks in advance

David

[rsissons]

There is really no feature in IOS to do this. What you would need would be a Cisco product called Local Director.

As a workaround, you could however use NAT in the router. By mapping a static NAT translation to the primary web server's address and then having a script monitoring the availability of that local address by pinging it. If the ping fails, it could then kick of a script to delete the static NAT translation to the primary server and add one for the same global address but pointing to the backup server's local address.

It's not very elegant though.

[dalmada]

Hi, thanks for your reply.

where should I execute the script. On the router itself?How?

Thanks again.

David

[dalmada]

Hi,

thank rou again for your reply.

Could you please give me some further informatio on how should I implement this script. It is possible to run a script on a cico router 2611XM?Or I run the script on another host and with a tftp put a new configuration?

David

[michel.mueller]

Hi David,

You should have a look a the IOS SLB (Server Load Balancing) feature.

Unfortunately SLB is not available for the 2600 Plattform. It is available for cat6000 and 7200.

regards Michel

Link:

Configuring IOS Server Load Balancing with HTTP Probes in the Dispatched Mode

http://www.cisco.com/en/US/products/hw/modules/ps2706/products_configuration_example09186a0080094066.shtml

[dalmada]

Hi,

well I a can´t have a 7000.

In fact I have two 2611XM and I would have a way of doing the redirection using both routers. Can you guys figure out a way of doing that.

thanks in advance.

David

[michel.mueller]

Hi David,

Consider using a software based loadbalacer for the webserver.

(e.g. Resonate, Stonebeat Cluster, Veritas Cluster or linux-ha.org, www.linuxvirtualserver.org )

Without SLB there is no way for automatic failover with IOS.

regards Michel

[dalmada]

Hi Michel,

Thanks for your advices but ufortunately I can afford( for the moment) to use any of the software you have mentioned. Linux-ha it's probably free but I am using W2K. So I'm looking for an aproach with a minimum down time in such conditions. Do you have any other suggestions?

thanks

David

[t.baranski]

Your best bet may be to have your DNS server(s) respond to queries for the web server's IP address with both the primary server's IP and the backup server's IP. Most web browsers will note that multiple IP addresses have been returned in the DNS response and, if the first one they try doesn't respond, will start trying alternate IP's within a minute.

Note that the order in which DNS returns multiple IP addresses is random, so you'll need to have both web servers active at all times, and traffic will be load balanced between them.