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Loop Prevention (Routers)
- Split horizon in distance-vector Routing Protocols
- When using split horizon, a routing protocol tries to prevent a routing loop. It does this by not advertising a route from an interface from which it received an advertisement for that route. Simply: The split horizon rule prohibits a router from advertising a route through an interface that the router itself uses to reach that destination network.
- Poison Reverse
- Distance-vector routing protocols in computer networks use route poisoning to indicate to other routers that a route is no longer reachable and should be removed from their routing tables.
- The minimum fields needed in a routing table:
|Mask||The network prefix (in CIDR notation) of the destination network|
|Network address||The network address of the destination network|
|The network interface used to get to the next hop router. |
a.k.a. “Exit Interface”
Think… From the router you’re on, which interface do I have to send the packet out of, to get it to the Next Hop router?
|Next Hop IP address||The IP address of the next neighbor router to the destination network. |
Think… From the router I am on, what is the IP address of the closest router I can forward the packet to, to get that packet to the destination network?
Lab-03: Building Routing Tables
- Lab-03: Network Diagram (PDF)
- Lab-03: Worksheet with Router A Complete (rtf)
- Lab-03: Empty Worksheet (rtf)
- You must be in class to get credit for this lab.
- You must complete the routing table for all routers and hand in the completed worksheet at the beginning of the next class, to get full credit for this lab.
Read / Do
- CCNA Routing and Switching Study Guide, 2nd Ed.: Chapter 18: OSPF
- Do the Chapter: Written Lab, Review Questions, AND Hands-on Labs
- Note: Until further notice, bring your text book to every class, so that you’ll have access to the instructions for the Hands-on Labs.
- Practice the Hands-on Labs
- Cisco 3750 series switch (1/0/1 = Stack member number / Module Number / Port Number )
- Cisco IOS and Router Command Reference