CCNP (Cisco Certified Network Professional) Route Certification Exam Cram Notes

3. Layer3 Technologies

3.3 Configure and verify static routing

Configured by the administrator manually. The administrator must also update the table manually every time a change to the network takes place. Static routes are commonly used when routing from a network to a stub (a network with a single route) network.

Correct command syntax for creating static route in cisco router is

ip route <destinaiton_network_address> <subnet_mask> < default_gateway>"

ip route network <mask address/interface> [distance]

ex: ip route 165.44.34.0 255.255.255.0 165.44.56.5

Here, 165.44.34.0 is the destination network or subnet 255.255.255.0 is the subnet mask 165.44.56.5 is the default gateway.

3.4. Configure and verify default routing

The default route (gateway of last resort) is used when a route is not known or is infeasible. The command is

ip route 0.0.0.0 0.0.0.0 165.44.56.5

The default gateway is set to 165.44.56.5

Default routes are used to direct packets addressed to networks not explicitly listed in the routing table. Default routes are widely used where learning specific networks is not feasible or desirable, as in case of stub networks, or limitations due to hardware and software resources.

There are three types of default routes:

1. ip default-gateway - It should only be used when ip routing is disabled on the Cisco router.

2. ip default-network - Unlike the ip default-gateway command, you can use ip default-network when ip routing is enabled on the Cisco router. The device considers the default network as the route to any ip address that is not on any attached/connected interfaces, or in its routing table. Default gateway need to configure on every router to get path for unknown destination packets.By using Default network command you need to configure only on one router in the network, so other routers can learn the exit gate by using routing protocol which distribute this information to others.

3. ip route 0.0.0.0 0.0.0.0 - The ip route command is used with static routing, whereas the ip default-network command is used mostly with routing protocols. Both are achieving the same goals but can be used in different scenarios. If you have a routing protocol for a domain, and you would like to advertise to the rest of the routers that a default route, you would implement the ip default-network command. This would cause the routing protocol to carry the candidate for default network in its routing updates to all routers in the domain.

The ip route 0.0.0.0 0.0.0.0 is a command that is statically assigned. This is called a default network because the all-zeros syntax means to catch all routes. The ip route command is not automatically carried in routing updates like the ip default-network command is in some routing protocols. You must redistribute the static command into a routing protocol for it to be carried.

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