Configure and verify static routing
Exam: Cisco 300-101 - Implementing Cisco IP Routing (ROUTE v2.0)
We will now discuss the topic “Configure and verify static routing” that comes under the exam number 300-101 Route. It is important from the exam point of view so try to prepare it on the lines of this chapter. The CCNP exam is a closed book exam so you must try to prepare the topic well.
As we all know that the routers do the job of forwarding route information from the route tables’ entries that are manually configured or the route information that is calculated using the dynamic routing algorithms. The static route is the explicit path between the two routers. These cannot be updated automatically.
This is why the static routes must be configured manually during the network change. The static routes will always use less bandwidth compared to the dynamic routes. The CPU cycles are not used to calculate the routing updates. The dynamic routes can be supplemented with static routes if there is a requirement.
The static routes can also be distributed into dynamic routes but the dynamic cannot be distributed into the static routes. The static routes can be used in network where the traffic can be predicted. It can also be used in a network where the design is simple.
The static cannot be used in a network that changes a lot as it is not very adaptable to changes. This is one reasons that dynamic routes is mostly is used in networks. The static routes give a specific gateway of last resort.
The administrative distance is the metric that is used by routers to choose the best path when there are two routes to the same destination. With the help of this you can choose one routing protocol over the other. This is useful when more than one protocol is added to the same route in a unicast routing table.
The routing protocols must be prioritized from the most to the least reliable one using the administrative distance. The static routes generally by default will have an administrative distance of 1.
A router will always prefers a static route over a dynamic route this happens because the route with a low number is always considered to be the shortest one. If as a network administrator you want the dynamic route to override the static route you must clearly specify the administrative distance of the static route.
Directly connected static routes
You must remember that the output interface must be specified always if you are using a directly connected static route. The router by default assumes that the destination is directly attached to the output interface and the packet destination is being used as the next hop address. The next hop address is a feature that can work only for point to point interfaces.
Fully specified static routes
In this route the network administrator must specifically mention the output interface or the next hop address in a static route that is completely specified. It can be used when the output interface is a multi-access interface. For this to happen the next hop address must be directly attached to the output interface that has been specified.
Floating static routes
This is like a back up for a dynamic router. It is mainly used by the static routers. The floating static route must always be configured with a higher administrative distance than the dynamic route that is being backed up. If the dynamic route is lost then the floating static route can be used as a replacement.
Remote next hops for static routes
In this routes you can specify the next hop address of the neighbouring router that is not directly connected to the router. It can be easily connected to static routes with remote. In case a static route has a remote next hop then these are used for unicast routing table for corresponding directly to the remote next hops.
BFD means bidirectional forwarding detection. It is basically used detecting protocol design. It provides a fast forwarding path failure detection at times. It can also be used to detect the subsecond failure detection that can happen between two devices. It is less CPU intensive too compared to many others.
The static routing will support VRF (virtual routing and forwarding) always. The VRF can be located within the VDC. Cisco will always place you in a default VRF and VDC. If you want a different one you will have to configure the same.
Licensing requirement for static routing
The static routing does not need any license. If you want any other feature that is not a part of the package you will have to pay an extra charge for that.
Prerequisites for static routing
As a network administrator you must be aware of the prerequisite of a static routing. It states that if the next hop address for the static routing is not reachable then the static route will not be added to the unicast routing table. Similarly the static routing also has a limitation and that is next hop address for static route can only be set for point to point interface like the GRE (generic routing encapsulation).
Configuring the static routes
The static route can be set on a router. You must ensure that you are in the correct VDC. To get this you can use the switchto vdc command. Once you get into the configuration mode. You must configure the static route and the interface for the static route. You can also display the list of the supported interfaces.
Using the null you can specify the interface as null. The next hop address can also be set but that is optional. You must set the administrative distance to anything between 1 to 255. Using the show ip static route command you can also display the information about the static routes. The last command that is used is copy running config start-up config this is an optional command and will save the configuration changes.
We hope that this chapter on “Configure and verify static routing” will help you to understand the concept better and help you to prepare better for the CCNP exam. We wish that you do well in the exam and get a good score.
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