questions on HTTP::header replace Host

Hi,dear irule

 

 

I have 2 datacenters,due to some operation,we need to forward traffic on site1 to site2

 

site1 and site2 have the same domain name www.cjj.com

 

However ,they can be different in order to achieve goal of forwarding traffic

 

like www1.cjj.com ,www2.cjj.com(I can change something to achieve this)

 

 

for example ,clients visit www.cjj.com and hit site1,when bigip receive this traffic ,forward it to site2 and keep the broswer same as before.

 

how to achieve this?

 

I searched the irule here,HTTP::header replace Host are used more often than other methods

 

But I am confused by events below

 

when HTTP_REQUEST {

 

if { [HTTP::header host] eq "www.cjj.com" } {

 

HTTP::header replace Host "www2.cjj.com" }

 

}

 

 

when HTTP_RESPONSE {

 

if { [HTTP::header is_redirect]} {

 

HTTP::header replace Location [string map -nocase {www.cjj.com www2.cjj.com} [HTTP::header value Location]] }

 

}

 

 

Here is my doubts:

 

 

1:why should we use HTTP_RESPONSE to change the location?

 

2:should I set node xxx under HTTP::header replace Host "www2.cjj.com"

 

like

 

HTTP::header replace Host "www2.cjj.com"

 

node xxxxip xxport

 

3:what is the process of this command ,after excuting this replace,what is the behavior of bigip to handle traffic(I know http::redirect is bigip send 30x to client and the client send request to new URL )

 

4:how to achieve this goal :forward traffic which hit site1 to site2 ,can I not need two domain name to achieve this?

 

Thanks in advance