Redirect HTTP:HOST incorrect

Hi all

We have a system: User >>> DNS local >> F5 >>> Web

When try test we access direct to web server ( member): http://dcebsapp01.education.mm:8000

Status: OK

But when we access via F5: via: https://erp.education.mm after enter we have check URL on web browser switch to: http://dcebsapp01.education.mm:8000/OA_HTML/AppsLocalLogin.jsp

We dont understand why it http:host not change to erp.education.mm ?

Please help us

Thank all

Hung Hoang