docs Submgt3 Cpe Ip Addr Prefix Len

This attribute represents the prefix length associated with the IP subnet prefix either set from provisioning or learned via address gleaning or other forwarding means. For IPv4 CPE addresses this attribute generally reports the value 32 (32 bits) to indicate a unicast IPv4 address. For IPv6, this attribute represents either an IPv6 unicast address (128 bits, equal to /128 prefix length) or a subnet prefix length (for example 56 bits, equal to /56 prefix length).