Does Routing Table contain Subnet Mask

[akshaycjoshi]

I am reading one book on ICND1.

It begins by telling what Ip address is, its classes.

It then tells how a single class A/B/C network can further be subdivided using subnet masks.

Without the subnetting, routers just store Network address and the interface to forward the packet.

With subnetting involved, does it store Subnet mask also, along with network address and IP address.

[Giuseppe Larosa · Accepted solution]

Hello Akshay,

yes indeed

IP prefixes are installed in the IP routing table with their own prefix length ( that is the subnet mask).

when selecting the route to use to route a packet the most specific route is used.

administrative distance is used to solve a tie between two prefixes with the same prefix length only the winner is installed in the IP routing table.

There is also the concept of classless routing: since IOS 12.0 a default route can be used to reach unknown subnets of a major network to which the router is connected to. classful routing doesn't use a default route for unknown subnets of an attached major network.

classless routing is the default since 12.0

Hope to help

Giuseppe

[akshaycjoshi]

Thanks