I am running Linux AS4 Update version. I have one lan card and the primary IP-Address is 192.168.0.215 & subnet is 255.255.255.0

Now I want to assign an alternative IP-Address on the same card & the IP I want to assign is 192.168.15.215.

I run the following command from root user
ifconfig eth0:1 192.168.15.215 netmask 255.255.255.0 up

Now when I ping this IP 192.168.15.215 From Windows machine then its reply me & properly reply comming from this Ip. But when I want to access this Ip by \\192.168.15.215 from run prompt then it gave me error.
The specified network name is no longer available..

I already restart the machine & network service but the problem remains same.

Please guide.

What service are you trying to access from the run command ? Just because you have added a new ip to the card doesn't mean any service is listening on that ip.

Is there now a file for the alias eth0:1 in /etc/sysconfig/network-scripts/ ?

Have you tried running
route add -host 192.168.15.215 dev eth0

man route

Have you tried setting this up using the GUI ?
https://www.redhat.com/docs/manuals/...k-aliases.html

This page has some more information.

Sounds like your web server is not assigned to that ip.