For LPM IP forwarding, it is often beneficial to use a narrow width response for indirection because there are many more forwarding entries than next hops. For example, if there are one million IPv4 routes, but only 32K next hops, a 15-bit wide response is sufficient to point out the next hops. Indirection is also useful for other purposes; if a next hop changes, only the next hop entry needs to be modified instead of thousands of forwarding entries.
IPv4 and IPv6 routes can be stored in the same CAM. When doing so IPv6 prefixes use all prefix lengths between 0 to 128, while IPv4 routes use prefix lengths 0 to 32.
VPN routes are also supported. The constant field in the most significant bits of the key should be used for storing the VPN number. The least significant bit of the constant field has a special purpose and should be used to differentiate between IPv4 and IPv6 entries. This way all the masks used for IPv6 are not be activated for IPv4 lookups, thus saving power.