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Prof. Alfred J Bird, Ph.D., NBCT http://www.cs.umb.edu/~abird abird@cs.umb.edu Office – Science 3rd floor – S-03-130 Office Hours – Monday and Thursday 3:00 to 4:00
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A router decides where to sent the packet next Works at layer 2 (Data Link) Routing Tables Routing Rules (How does it decide?) Routers are often set up in a mesh topology Gateway Address Network Segments
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Uses layer 3 addressing for selecting routes Isolates segments, broadcast domains Determines where to send the packet next Look at figure 7-2 on page 291 Default Gateway Address
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RS-232 DB-9 DB-25 How do we configure the router when we first turn it on? Cisco IOS Exec Mode Privileged Exec Mode Look at Figure 7-20 on page 314
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What is a Routing Protocol Routing Protocols provide a standardized format for route management including route selection, sharing route status with neighboring routers and calculating alternative routes if the best path route is down.
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There are basically two types of routing protocols Static protocols Dynamic Protocols
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Static Route A static route is list of IP addresses to which data traffic can be forwarded and has been entered manually into either a router’s or a computer’s routing table.
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Variable Length Subnet Masking Routes can be configured using different length subnet masks Look at the previous example The 10.10.200.0 subnet only needs four (4) IP addresses, so why would we want to use more. What are the four (4) needed IP addresses?
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What is the path from A1 on LAN A to B1 on LAN B? A1 LAN A – 10.10.20.1 FA0/0 on ROUTER A – 10.10.20.250 FA0/1 on Router A – 10.10.200.1 FA0/2 on Router B – 10.10.200.2 FA0/0 on Router B – 10.10.10.250 B1 on LAN B – 10.10.10.1 So we must program this information manually!
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What is the Gateway of Last Resort? The IP Address of the router in your network whare data packets with unknown routes should be forwarded. The purpose is to configure a route for data packets the do not have a destination route configured in the routing table. ip route 0.0.0.0 0.0.0.0
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There are two basic classes of Dynamic Routing Protocols: Distance Vector Protocol Link State Protocols There are also hybrid protocols These are a combination of the two basic protocols
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The primary features of a dynamic routing protocol are: What information is exchanged between routers. When updated routing information is exchanged. Steps for reacting to changes in the network. Criteria for establishing the best route selection.
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Path Determination Procedure to determine best route Metric A numeric measure assigned to routes Convergence Time it takes for the router to obtain a clear view of the routes Load Balancing Allowing the router to use multiple data paths
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Hop Count Reliability Bandwidth Delay Cost Load Ticks
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A distance Vector Protocol periodically sends it routing table to its neighbors or adjacent routers. When the neighboring router receives a table, it assigns a distance vector to each route. The distance vector is typically specified by some metric such as hop count.
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RIP Created in 1988 Uses hop count Maximum number of hops is 15 Exchanges tables every 30 seconds Can consume a lot of bandwidth Slow convergence
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A Link State Protocol establishes a relationship with neighboring routers and uses route advertisements to build a routing table. Key Issues: Finds neighbors/adjacencies Uses route advertisements to build routing tables Sends “Hello” packets Send updates when routing changes. Also called Shortest Path First Protocols Based upon the work of E. W. Dijkstra
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OSPF (Open Shortest Path First) Developed by the IGP (Interior Gateway Protocol) working group of the IETF (Internet Engineering Task Force) It is an open (non-proprietary) protocol Supported by many vendors Has rapid convergence It consumes very little bandwidth Difficult to configure Uses VLSM
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IS-IS (Intermediate System to Intermediate System) Very similar to OSPF Designed as part of the OSI network layer service
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EIGRP (Enhanced Interior Gateway Routing Protocol) A Cisco proprietary protocol. Combines both distance vector and link state algorithm. An enhanced version of the IGRP protocol
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Load the CD Software. Go to page 303, section 7-4 in the textbook Follow along with the activity. Record all the results from your actions. Go to page 309, section 7-5 in the textbook Follow along with the activity. Record all the results from your actions. Submit a report when you have completed the activity.
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Load the CD Software. Go to page 368, section 9-2 in the textbook Follow along with the activity. Go to page 387, section 9-7 in the textbook. Follow along with the activity. Record all the results from your actions. Submit a report when you have completed the activity.
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