1. Distance Vector Routing Protocols
Module 7
Distance Vector Routing Protocols

2. RECALL: Dynamic Routing
Dynamic routing refers to the process of allowing the router to determine the path to the destination.
avoid the time-consuming process of configuring static routes
Routing protocols enable dynamic routing where multiple paths to the same destination exist.

3. Distance Vector Routing Updates
Routing table updates occur:
_______________________________
__________________________________________________________________
Recall: Router to send its entire routing table to each of its _______ ___________________________
Contents include: information about the _______________________________

4. Routing Loop Problem TALK ABOUT EXAMPLE
Just before the failure of Network 1, all routers have consistent knowledge and correct routing tables. The network is said to have converged. Assume for the remainder of this example that Router C's preferred path to Network 1 is by way of Router B, and the distance from Router C to Network 1 is 3.
When Network 1 fails, Router E sends an update to Router A. Router A stops routing packets to Network 1, but Routers B, C, and D continue to do so because they have not yet been informed of the failure. When Router A sends out its update, Routers B and D stop routing to Network 1. However, Router C has not received an update. To Router C, Network 1 is still reachable via Router B.
Now Router C sends a periodic update to Router D, indicating a path to Network 1 by way of Router B. Router D changes its routing table to reflect this good, but incorrect, information, and propagates the information to Router A. Router A propagates the information to Routers B and E, and so on. Any packet destined for Network 1 will now loop from Router C to B to A to D and back to again to C.

5. Counting to Infinity
__________ ____________________________________________________________________________________
__________________ allows a routing loop and the count to infinity problems to exist.

6. Solution (to count to infinity)
Protocols define -__________________ ______________________________.
When metric exceeds its maximum allowed value, _______________________________ ___________________________________
Examples:
RIP- max of 15 hop counts

7. Another Solution (Split Horizon)
A routing update regarding a certain network, __________________________ ____________________________________________________________________.

8. Split Horizon
Split-horizon attempts to avoid this situation. If a routing update about Network 1 arrives from Router A, Router B or Router D cannot send information about Network 1 back to Router A. Split-horizon thus reduces incorrect routing information and reduces routing overhead

9. Another Solution (Route Poisoning)

10. Route Poisoning
Causes an ____________________ _______________ for a failed route
The router that receives the poison update will then _______________ _____________________, called a poison reverse. This ensures all routes on the segment have received the poisoned route information.

11. Triggered Updates
______________________________________________________________________________________
Instead of waiting the protocol’s default time to send the update

12. Another Solution (Hold-down timers)
When a router receives an update from a neighbor indicating a network is down, _______________________________ ________________________________________________________________
Only under certain circumstances is that hold-down timer removed
Hold-down timer allows time for _______________________________

13. Holddown Timers

14. Enabling RIP and IGRP In Global configuation mode
______________________________________
In router config mode
____________________________________________________

15. RIP specifics It is a distance-vector routing protocol.
____________________________________________________________________________
Max. _______________________________
After that destination assumed unreachable
By default, ___________________________ ___________________________________
Ex command: Router(config)# _____________

16. Rip cont…
When a router receives a routing update that contains a new or changed entry, __________ ________________________________________________________________________
Can maintain _________________________ ____________________________
Can be configured on serial interfaces to _____ __________________________________________________________________________
ip rip triggered command

17. RIP Configuration

18. RIP and classless
If “ip classless” is disabled and one part of a major network is known, but the ______ __________________________________________________________________
If a default route is configured, ______ _______________________________
Configuring ip classless on a router will solve this problem therefore…
ip classless command is enabled by default in Cisco IOS v and later

19. RIP commands Know when and how to use the RIP commands such as
_______________________
Default ___________________
can be configured for _________________ _________________________________________________________________________________
________________________
The ideal setting would be to set the timer just __________________________________________________________________________________

20. Example of Classless routing

21. IGRP specifics ___________________________________ routing protocol
Scalable to larger networks
By default, routing updates are _______________ _______________________________________
______________________________ are the two characteristics used to generate the metric, ___________________________
_______________ other characteristics which can be set
Example global command
router(config)# router igrp 2
router(config-router)# network
Autonomous System number
- required

22. General Commands
Verify and troubleshoot RIP and IGRP configurations with the following commands…
Show ip route
Show ip protocol
show interface interface
show ip interface interface
show running-config
debug ip rip

23. Command detail
show ip interfaces

24. Another SHOW command show ip protocol
Associated with the ______________________

25. Another SHOW command cont…
show ip route
Essential for troubleshooting networks

26. Lastly… Debug commands
Powerful but ___________________________ __________________________________
Allow _________________________________
Basically another "show" command
Example:
“debug ip rip “
command displays RIP routing updates as they are sent and received (in real time)
Use “no debug ip rip” or “no debug all” to turn debugging off

27. Labs to complete Lab 7-1 Configuring RIP Lab 7-2 Troubleshooting RIP
Lab 7-3 Preventing Routing Updates Through an Interface
Lab 7-4 Load Balancing Across Multiple Paths
Optional Lab 7-5 Configuring Interior Gateway Routing Protocol