How to Add IP Routes and Set a Default Route

It is clear that Internet was not around a router. Normally, go to another system needs at least one other router (possibly more). This also may be a single interface can have multiple networks. General form of Cisco's routing command is

ip route <network> <mask> <interface/next-hop> [metric]

Metric is determined by some routing protocols (RIP on the other router to the network "distance" when prompted for advertising the route to other routers. Under normal circumstances, you can omit the metric, the default value is assigned to the routing protocol.

Examples:

 Add a route for 202.123.100.0 (class C) through 204.203.12.1.

  ip route 202.123.100.0 255.255.255.0 204.203.12.1
Add 122.250.0.0 (class B) to ethernet0

  ip route 122.250.0.0 255.255.0.0 Ethernet0

Classless Inter-Domain Routing:

With the recent explosive growth of the Internet, addresses are divided into classes a, b, c, and d networks are no longer enough. Cisco IOS support Classless Inter-domain routing, or CIDR entries (often clearly "Apple juice") allows a subset of any type for the given network, given the destination routing concepts. For example, the following example specify the route 8 CS router.

 ip route 221.243.242.0 255.255.248.0 128.230.3.1

Please note changes from the above examples are just different screen. This command uses the subnet mask-style split in early August by 221.243.250.0 class c network, and lists as a next hop router 128.230.3.1. Under normal circumstances, 8 routes will be needed to complete this one did. CIDR routing when the objective is to simplify and reduce Internet routing tables (such as Sprint, ANS and Alternet) reaches the point where the old backbone network by just does not have enough memory to accommodate the Internet tables folded they did not work to prevent the entire routing table size. This Internet service interruption caused severe damage around the world.

Often use a practice of subnetting class c network into 64 or 32 IP address blocks for customers all 254 addresses are required to save wasting large numbers. Traditional class c subnetting allows you to be split into blocks of 4, 8, 16, 32, 64, and 128, but only one size. Cisco IOS supports variable-length subnetting, however. This subparagraph allows a class c, which may have some part 4 addresses the length, some on 32, and so on. That allows to eliminate only going to use 6-bit customers sent 32 addresses the need to more effectively address.

Subnet be noted IOS does not generally allow you to specify a class c subnet mask addresses (IE, you cannot route 8 address 203.102.123.0 subnet because this is a class c network number, it wants to be regarded as class c, route). When you view the routing table, this can cause some confusion. To work around this problem, Cisco provides a command to override this behavior:

  ip subnet-zero
Once that has been entered, it will very happily take the subnet route.