what is the subnet mask for this hst IP prefix format ? Host IP Address: 183.91.104.16
/26
/28
5
It does not require a subnet mask.
If this is a default subnet mask, then it would be a class C subnet mask. If you are subnetting a network and this is not the default subnet mask, then it could be either a class A or class B.
Subnet mask
The default subnet mask has a standard size. The custom subnet mask allows you to make subnets that are smaller or larger than the default.
RIP VERSIONV1 can be seen to exclude subnet information from routing updates, this is because ripv1 is a classful routing protocol and does not support VSLM, this was corrected in RIPv2 where ripv2 does send out subnet mask's in the form of a prefix eg /24 which is the subnet mask of 255.255.255.0 or a class c address.
2 given subnets
255.255.255.0
255.255.255.0
The default subnet mask would be 255.255.0.0 for a class B address.