AuthHound

RADIUS attribute 8 · type ipaddr

Framed-IP-Address

Framed-IP-Address (attribute 8) is the IPv4 address RADIUS assigns to a session, most often on VPN and PPP access rather than 802.1X.

Also searched as: assigned IP attribute. Defined in RFC 2865.

What it means

In an Access-Accept, Framed-IP-Address tells the NAS which IPv4 address to give the connecting user. The value 255.255.255.255 means "let the NAS pick from its own pool" and 255.255.255.254 means "negotiate an address"; a real address pins the session to that IP. On 802.1X switch ports this attribute is usually irrelevant — it belongs to the VPN/PPP world.

How it's used

Return a concrete address for fixed per-user IPs, or the sentinel values to defer to the NAS pool. In accounting packets the same attribute reports the address that was actually assigned.

Values

  • 255.255.255.255 — The NAS should assign an address from its own pool.
  • 255.255.255.254 — The NAS should allow the user to negotiate an address.

Common gotchas

  • Returning a fixed Framed-IP-Address that isn't in a subnet the NAS routes leaves the session up but unreachable.

Related

When a NAS quietly stops honoring an attribute across a fleet, nobody sees it until users complain. AuthHound is building monitoring that tracks the attributes your servers actually return — early access:

No spam, no sharing — one email when it's ready, and you can reply to be removed anytime.