This object indicates the ifIndex of the link (LAN port) through which IPCP Subnet Mask negotiation is allowed. The distinguished value of zero may be used if no link is enabled for IPCP Subnet Mask negotiation. For LA-110, IPCP Subnet Mask support allows Customer Premises Equipment (CPE) to connect to a Broadband Access Server (BAS) and obtain an IP address and subnet range that the CPE can use to populate the DHCP server database. The IP address is also used to configure an IP interface over the LAN port. The IP Address is dynamically allocated by the DHCP Server, using the DHCP Pool that was allocated over the PPP connection. In order to connect one of the LANs to Subnet Mask Negotiation, its IP Address should be 0.0.0.0. When the IP Address is allocated from the PPP, the 0.0.0.0 IP Address is replaced in the data base by the allocated IP Address. Only one Subnet Mask Negotiation on WAN interface can be enabled at the same time in order to avoid allocating the LAN IP address according to a few WAN interfaces (a one-on-one connection). The linked LAN interface can be deleted only after disabling the Subnet Mask Negotiation on the PPP connection.