I-rule redirection

You can redirect from http://www.xyz.com to https://a1.www2.xyz.com with a Policy or iRule with easy on the F5 LTM.

iRule would be as follows, just update the FQDNs and apply to your HTTP Virtual Server:

when HTTP_REQUEST {
    if {[string tolower [HTTP::host]] eq "www.xyz.com"} {
        HTTP::redirect "https://a1.www2.xyz.com[HTTP::uri]"
    }
} 

Alternatively if you want to only redirect if the client sends a request for a1.www2.xyz.com then the following should work:

when HTTP_REQUEST {
    if {[string tolower [HTTP::host]] eq "a1.www2.xyz.com"} {
        HTTP::redirect "https://[HTTP::host][HTTP::uri]"
    }
}