Are you talking about changing source address in IP header? Most ISPs will drop such packets:
<a href="https:&#x2F;&#x2F;tools.ietf.org&#x2F;html&#x2F;rfc3013#section-4.3" rel="nofollow">https:&#x2F;&#x2F;tools.ietf.org&#x2F;html&#x2F;rfc3013#section-4.3</a>