The netmask features of ripd support both version 1 and version 2 of
RIP. Version 1 of RIP originally contained no netmask information. In
RIP version 1, network classes were originally used to determine the
size of the netmask. Class A networks use 8 bits of mask, Class B
networks use 16 bits of masks, while Class C networks use 24 bits of
mask. Today, the most widely used method of a network mask is assigned
to the packet on the basis of the interface that received the packet.
Version 2 of RIP supports a variable length subnet mask (VLSM). By
extending the subnet mask, the mask can be divided and reused. Each
subnet can be used for different purposes such as large to middle size
LANs and WAN links. Quagga ripd does not support the non-sequential
netmasks that are included in RIP Version 2.
In a case of similar information with the same prefix and metric, the old information will be suppressed. Ripd does not currently support equal cost multipath routing.