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2.2.1.2 NAP-Mask Option

If the DHCP server determines that the DHCP client must be quarantined, it overrides the administrator-configured IPv4 subnet mask for that subnet and instead sends 255.255.255.255 as the subnet mask in DHCP option 1 (as specified in [RFC2132] section 3.3). In this case, the original subnet mask configured by the administrator MUST be sent as a vendor-specific option to the client in little-endian byte order. The original subnet mask MAY be used by clients that do not support classless static routes and that rely on the DHCP Static Route option defined in [RFC2132] for their routing information.<1>

This vendor-specific option MUST be encapsulated inside option 43, as specified in [RFC2132] section 8.4.

The NAP Subnet Mask (NAP-Mask) option is defined as follows.


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Vendor-Specific_Option_Code

Vendor-Specific_Option_Length

Vendor-Specific_Option_Data

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Vendor-Specific_Option_Code (1 byte): This MUST be 0xDD.

 

Vendor-Specific_Option_Length (1 byte): This MUST be 0x04.

 

Vendor-Specific_Option_Data (4 bytes): Subnet mask in little-endian byte order.

 
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