Logon with URL parameter not possible; logon cookie is missing

Dear Expert,

We are in process of implementing the Dual URL for the single SAP Portal 7.4 system.

eg :

URL 1: http://aaa.yy.com:<port>/irj/portal

URL 2: http://bbb.xx.org:<port>/irj/portal

So we have maintained the dual entry as like above in our DNS server.

But we are facing the below error while accessing the backend system(ECC ) through the URL 2 and getting the below error in login page.

its is working fine with URL 1 option.

"Logon with URL parameter not possible; logon cookie is missing"

Please provide us  your valuable suggestion to achieve the same.

Regards

Sebastian A