The framed IPv4 address is one of the many RADIUS attributes and it indicates the address assigned to the client. The attribute may be included in the access-request packet. When sent in an access-request packet, the IP address is sent as a hint to the RADIUS server. The Framed-IP-Address field is included in the access-request packets sent to RADIUS servers during authentication.

The RADIUS Attribute 8 (Framed-IP-Address) in Access Requests feature makes it possible to run applications on the RADIUS server that builds mapping tables of users and IP addresses. The server can then use the mapping table information in other applications, such as preparing customized user login pages in advance of a successful user authentication with the RADIUS server.

Reference link:

https://www.juniper.net/documentation/us/en/software/junos/user-access/topics/topic-map/802-1x-and-mac-radius-accounting.html

Enabling DHCP-SNOOPING will automatically enable Framed-IP-address (The IP address of the authenticated user) attribute. CLI configuration not required.

The Framed-IP-Address attribute is sent only if a valid DHCP binding exists for the host in the DHCP snooping table.