how to redirect domain according to country IP address

Check that you have the mod_geoip module (GeoIP Extension) installed on your server.

Then, tweak your .htaccess file accordingly :

GeoIPEnable On
GeoIPDBFile /path/to/GeoIP.dat

# Start Redirecting countries

# Canada
RewriteEngine on
RewriteCond %{ENV:GEOIP_COUNTRY_CODE} ^CA$
RewriteRule ^(.*)$ http://ca.abcd.com$1 [L]

# India
RewriteEngine on
RewriteCond %{ENV:GEOIP_COUNTRY_CODE} ^IN$
RewriteRule ^(.*)$ http://in.abcd.com$1 [L]

# etc etc etc...

And here's the official documentation.