1. Static Routing CCNA Routing and Switching Semester 2 Chapter 6
28/04/2017
Static Routing
CCNA Routing and Switching Semester 2
Chapter 6
Thanks to S Ward Abingdon and Witney College and St. Clair College in Windsor, Ontario and Cisco Networking Academy Slides.
S Ward Abingdon and Witney College

2. Topics Static routes Summary and default routes
Forwarding with static routes
Managing and troubleshooting static routes

3. Reach Remote Networks
A router can learn about remote networks in one of two ways:
Manually - Remote networks are manually entered into the route table using static routes.
Dynamically - Remote routes are automatically learned using a dynamic routing protocol.
Reach Remote Networks

4. Static Routing Why Use Static Routing?
Advantages over dynamic routing:
not advertised over the network, resulting in better security.
use less bandwidth than dynamic routing protocols, no CPU cycles are used to calculate and communicate routes.
the path a static route uses to send data is known.
Why Use Static Routing?

5. Static Routing Why Use Static Routing? (cont.)
disadvantages:
Initial configuration and maintenance is time-consuming.
Configuration is error-prone, especially in large networks.
Administrator intervention is required to maintain changing route information.
Why Use Static Routing?

6. Static Routing Why Use Static Routing? (cont.)
disadvantages:
Does not scale well with growing networks; maintenance becomes cumbersome.
Requires complete knowledge of the whole network for proper implementation.
Why Use Static Routing?

7. Static Routing When to Use Static Routes
Static routing has three primary uses:
Providing ease of routing table maintenance in smaller networks that are not expected to grow significantly.
Routing to and from stub networks.
Using a single default route to represent a path to any network that does not have a more specific match with another route in the routing table.
When to Use Static Routes

8. Types of Static Routes Static Route Applications
Static Routes are often used to:
Connect to a specific network.
Provide a Gateway of Last Resort for a stub network.
Reduce the number of routes advertised by summarizing several contiguous networks as one static route.
Create a backup route in case a primary route link fails.
Static Route Applications

9. Types of Static Routes Standard Static Route
Stub Network:
A network accessed by a single route.
Running a dynamic routing protocol between R1 and R2 is a waste of resources.
Static routes are commonly used when routing from a stub network.

10. Types of Static Routes Default Static Route
A route that matches all packets.
Identifies the gateway IP address to which the router sends all IP packets that it does not have a learned or static route.
Simply a static route with /0 as the destination IPv4 address.
Default Static Route
Stub network
Static route
Default route

11. Types of Static Routes Summary Static Route

12. Types of Static Routes Floating Static Route
Floating static routes are static routes that are used to provide a backup path to a primary static or dynamic route, in the event of a link failure.
The floating static route is only used when the primary route is not available.
To accomplish this, the floating static route is configured with a higher administrative distance than the primary route.
Floating Static Route

13. Configure IPv4 Static Routes ip route CommandOR

14. Configure IPv4 Static Routes Next-Hop Options
Next-hop route - Only the next-hop IP address is specified.
Directly connected static route - Only the router exit interface is specified.
Fully specified static route - The next-hop IP address and exit interface are specified.
Next-Hop Options

15. Configure IPv4 Static Routes Configure a Next-Hop Static Route
R1 only knows its directly connected networks.

16. Configure IPv4 Static Routes Configure a Next-Hop Static Route
/ 24
/ 24
Add a static route to R1 for the LAN on R2.
Network
Subnet Mask
Next-Hop Address

17. Configure IPv4 Static Routes Configure a Next-Hop Static Route
/ 24
BEFORE
/ 24
AFTER
Add a static route to R1 for the LAN on R2.

18. Configure IPv4 Static Routes Static Routes Principles
Static Routing
28/04/2017
Configure IPv4 Static Routes Static Routes Principles
Or would a ‘ping’ from a PC on the LAN on R1 to a PC on the LAN on R3 work?
Would a ‘ping’ from a PC on the LAN on R1 to a PC on the LAN on R2 work?
Return Route?
S Ward Abingdon and Witney College

19. Configure IPv4 Static Routes Routing Table Principles and Static Routes

20. Verifying Static Routes

21. Verifying Static Routes

22. Configure IPv4 Static Routes Configure Directly Connected Static Route
Configure a Directly Connected Static Route

23. Configure IPv4 Static Routes Configure a Fully Specified Static Route
Both the output interface and the next-hop IP address are specified.
This is another type of static route that is used in older IOSs, prior to CEF.
This form of static route is used when the output interface is a multi-access interface and it is necessary to explicitly identify the next hop.
The next hop must be directly connected to the specified exit interface.
Configure a Fully Specified Static Route

24. Resolving to an Exit Interface
Packet for
Before any packet is forwarded by a router, the routing table process must determine the exit interface to use to forward the packet.
When the router has to perform multiple lookups in the routing table before forwarding a packet, it is performing a process known as a Recursive Route Lookup.

25. Exit Interface is Down
BEFORE
AFTER
Cannot have a route if the exit interface does not exist.
If an interface is manually taken down (shutdown) or a link fails, all routes that are resolved to that interface as the exit interface will be removed from the routing table.

26. Next hop or exit interface?
For a point to point serial link, configure the static route with the exit interface.
Only one look-up, less processing.
For an Ethernet link, configure the static route with the next hop address (or with both).
This identifies the device that should receive the packet next. The MAC address can be found and used in the frame header.

27. Static Routes with Ethernet Interfaces

28. Static Routes with Ethernet Interfaces
NOT Recommended
Recommended
Since many different devices can be sharing the same multi-access network, the Router will have difficulty determining the destination MAC address.
Use both the exit interface and next-hop address for Ethernet exit interfaces.

29. Summary Static Routes
Route Summarization:
A summary route is a single route that can be used to represent multiple routes.
Generally a set of contiguous networks.
Have the same exit interface or next-hop IP address.
Creates smaller routing tables
More efficient routing table lookup process.

30. Summary Static Routes R3 has three static routes configured.
All three routes are forwarding traffic out the same Serial 0/0/1 interface.
Can be summarized to / 22 ( )

31. Summary Static Routes

32. Summary Static Routes BEFORE AFTER
Any packet with a destination IP address belonging to the /24, /24, or /24 network matches this summarized route.

33. Configure Floating Static Routes Floating Static Routes
Floating static routes are static routes that have an administrative distance greater than the administrative distance of another static route or dynamic routes:
The administrative distance of a static route can be increased to make the route less desirable than that of another static route or a route learned through a dynamic routing protocol.
In this way, the static route “floats” and is not used when the route with the better administrative distance is active.
However, if the preferred route is lost, the floating static route can take over, and traffic can be sent through this alternate route.
Floating Static Routes

34. Configure Floating Static Routes Configure a Floating Static Route

35. Configure Floating Static Routes Test the Floating Static Route
To test a floating static route:
Use a show ip route command to verify that the routing table is using the default static route.
Use a traceroute command to follow the traffic flow out the primary route.
Disconnect the primary link or shutdown the primary exit interface.
Use a show ip route command to verify that the routing table is using the floating static route.
Use a traceroute command to follow the traffic flow out the backup route.
Test the Floating Static Route

36. Default route ip route 0.0.0.0 0.0.0.0 [ip address | interface]
Stub network
Static route
networks
Default route

37. Default Static Routes
ip route
ip route
A common use for static routes is connecting a company’s edge router to the ISP network.

38. Default Static Routes
A common use for static routes is connecting a company’s edge router to the ISP network.

39. Delete a static route
R1(config)#no ip route serial 0/0
Give the same command again with no in front.
Most commands can be reversed like this.

40. Configure IPv4 Static Routes Verify a Static Route
Along with ping and traceroute, useful commands to verify static routes include:
show ip route
show ip route static
show ip route network
Verify a Static Route