1. A method for atomically updating an access control list stored in a ternary content addressable memory (TCAM), the method comprising: receiving an update to apply to the access control list; identifying a first group of entries in the TCAM using an active version bit, wherein each entry in the first group has a ternary flag has a value matching a current value of the active version bit, wherein the ternary flag value indicates one of matching, not matching, or always matching the active version bit; updating the ternary flag value of one or more entries in the TCAM to define a second group of entries, wherein each entry in the second group of entries has ternary flag value of either not matching or always matching; and atomically performing the update by inverting the value of the active version bit.