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Transcript
Cisco 2 - Routers Chapter 4 Module 6 Routing & Routing Protocols Perrine modified by Brierley 5/25/2017 Page 1 Cisco 2 - Routers Routing Protocols Chapter 4 Important function of a router (layer 3 device): • Examine incoming data packets & make path selection based on: • information stored in its routing tables Router evaluates the available paths to a destination & establishes the best path for routing a packet. Most routing protocols use the shortest & best path - but each use different methods. Perrine modified by Brierley 5/25/2017 Page 2 Cisco 2 - Routers The Routing Process 192.168.1.56 01-00-A5-C3-26-6B Chapter 4 • The protocol address (IP) always remains the same. 192.168.1.56 34-7E-33-12-C9-20 192.168.1.56 6A-5F-0D-09-8B-AA 192.168.1.56 BC-48-03-8F-FF-AA Perrine modified by Brierley 5/25/2017 • The physical address (MAC) changes at each hop. Page 3 Cisco 2 - Routers Static Routing Chapter 4 Characteristics of static routes: • administrators establish static routing table maps • routes do not change, unless changed by an administrator • used in environments where network traffic is predicable & network design is simple • can’t react quickly to network changes; hence are considered unsuitable for today’s LANs Perrine modified by Brierley 5/25/2017 Page 4 Static Routing Cisco 2 - Routers Chapter 4 Static route can be defined in global config mode: RouterA(config)# ip route <dest network> <subnet mask> < interface | next hop> 192.16.10.1 s0 Network 200.10.10.0 Router A Router B RouterA(config)# ip route 200.10.10.0 255.255.255.0 192.16.10.1 RouterA(config)# ip route 200.10.10.0 255.255.255.0 s0 Perrine modified by Brierley 5/25/2017 Page 5 Cisco 2 - Routers s0 Static Routing Chapter 4 192.16.10.1 Network 200.10.10.0 Router A Router B e0 195.10.10.0 net The command for a static address from 195.10.10.0 to get to network 200.10.10.0 is: RouterA(config)# ip route 200.10.10.0 255.255.255.0 192.16.10.1 RouterA(config)# ip route 200.10.10.0 255.255.255.0 s0 Perrine modified by Brierley 5/25/2017 Page 6 Static Routing Cisco 2 - Routers s0 Chapter 4 192.16.10.1 Network 200.10.10.0 Router A Router B RouterA(config)# ip route 200.10.10.0 255.255.255.0 192.16.10.1 In the routing table, the above example will have an administrative distance of 1. RouterA(config)# ip route 200.10.10.0 255.255.255.0 s0 In the routing table, the above example will have an administrative distance of 0. Perrine modified by Brierley 5/25/2017 Page 7 Static Routing Cisco 2 - Routers s0 Chapter 4 192.16.10.1 Network 200.10.10.0 Router A Router B RouterA(config)# ip route 200.10.10.0 255.255.255.0 192.16.10.1 If the network 192.16.10.0 goes down for any reason, the static address on RouterA will be removed from the routing table. Perrine modified by Brierley 5/25/2017 Page 8 Cisco 2 - Routers Default Static Route (Gateway of Last Resort) Chapter 4 If router doesn’t know where to send a packet, it can use a default route: RouterA(config)# ip route 0.0.0.0 0.0.0.0 < interface | next hop> 192.16.10.1 s0 Router A Internet RouterA(config)# ip route 0.0.0.0 0.0.0.0 192.16.10.1 RouterA(config)# ip route 0.0.0.0 0.0.0.0 s0 Perrine modified by Brierley 5/25/2017 Page 9 Default/Static Route Cisco 2 - Routers Chapter 4 Verify a static route or default route with the commands: show running-config (s run) Or show ip route (s ip route) Test a static route or default route with the commands: ping Or traceroute Perrine modified by Brierley 5/25/2017 Page 10 Chapter 4 Configuring Static Routes with Outgoing Interface Cisco 2 - Routers Outgoing interface Administrative distance of 0 Perrine modified by Brierley 5/25/2017 Page 11 Cisco 2 - Routers Chapter 4 Configuring Static Routes with Next-hop IP Address Next hop interface Administrative distance of 1 default Perrine modified by Brierley 5/25/2017 Page 12 Cisco 2 - Routers Routed vs. Routing Protocols Chapter 4 Routed vs. Routing: Routed protocols are protocols that are moved over a network. (PCs use routed protocols to talk to each other.) • TCP/IP • IPX • Apple Talk … Perrine modified by Brierley 5/25/2017 Page 13 Cisco 2 - Routers Routed vs. Routing Protocols Chapter 4 Routed vs. Routing: Routing protocols route routed protocols through a network. (Routers use routing protocols to talk to each other about networks & paths.) • RIP (Routing Information Protocol) -- RIP Ver2 • IGRP (Interior Gateway Routing Protocol) • EIGRP ( Enhanced IGRP) • BGP (Border Gateway Protocol) • OSPF (Open Shortest Path First) • APPN (Advanced Peer-to-Peer Networking) • IS-IS (Intermediate System-to Intermediate System) Perrine modified by Brierley 5/25/2017 Page 14 Cisco 2 - Routers Autonomous Systems Chapter 4 An autonomous system (AS) is a collection of networks under a common administration. The American Registry of Internet Numbers (ARIN) assigns an identifying number to each AS. AS is a 16 bit number. Some routing protocols such as IGRP, EIGRP requires AS. Perrine modified by Brierley 5/25/2017 Page 15 Cisco 2 - Routers Routing Protocols Chapter 4 When all routers in an internetwork are operating with the same knowledge of the routes available in a network it is said to have converged. Fast convergence is desirable because it reduces the period of time in which routers would continue to make incorrect routing decisions. Perrine modified by Brierley 5/25/2017 Page 16 Cisco 2 - Routers Chapter 4 Routing protocols are divided into 2 classes: Interior and Exterior • interior - used for routing information within networks that are under a common network administrator • RIP • IGRP • OSPF • EIGRP Perrine modified by Brierley 5/25/2017 Page 17 Cisco 2 - Routers Chapter 4 Routing protocols are divided into 2 classes: Interior and Exterior Exterior - used for routing information between networks that do not share a common administrator. • EGP (exterior gateway protocol) • BGP (border gateway protocol) Perrine modified by Brierley 5/25/2017 Page 18 Cisco 2 - Routers Classes of Routing Protocols Chapter 4 Classes of Routing Protocols • distance-vector - determines the direction & distance • IGRP • RIP • link-state (also called shortest path first) recreates the exact topology of the entire network). • OSPF • IS-IS Perrine modified by Brierley 5/25/2017 Page 19 Cisco 2 - Routers Distance Vector Routing Protocols Chapter 4 Distance vector routing algorithms pass periodically copies of a routing table from router to router. These regular updates are based on the routing algorithm know as Bellman-Ford algorithm. However a distance vector algorithms do not allow a router to know the exact topology of an internetwork as each router only sees its neighbor routers. Perrine modified by Brierley 5/25/2017 Page 20 Cisco 2 - Routers Link-state Routing Protocol Chapter 4 Link-state algorithms are also known as Dijkstras algorithm or SPF (shortest path first) algorithm. Link-state routing algorithms maintain a complex database of topology information. It maintains full knowledge of distant routers and how they are interconnected. Link-state routing uses: • Link-state Advertisements (LSAs) Small packets of routing info that are sent between routers • SPF algorithm (shortest path first) • Topological database • Routing tables Perrine modified by Brierley 5/25/2017 Page 21 Cisco 2 - Routers Link-state Routing Protocol Chapter 4 Link-state makes an update only when there is a topology change. Link-state concerns itself with minimizing: • processor overhead • memory requirements • bandwidth consumption Perrine modified by Brierley 5/25/2017 Page 22 Cisco 2 - Routers RIP routing protocol Chapter 4 Characteristics of RIP are: • distance vector • metric is hop count • if the hop count is greater than 15, the packet is discarded • table is updated every 30 seconds Each router that a message has to go through to get to its destination is considered one hop count. If the message pass through 2 routers the hop count is 2. If the destination is the next router, then the hop count is 0. Perrine modified by Brierley 5/25/2017 Page 23 Cisco 2 - Routers IGRP Routing Protocol Chapter 4 IGRP: • must be assigned an AS (autonomous system number - 16 bit number) • Cisco proprietary • distance-vector • metrics • delay • bandwidth (1200 bps - 10 Gbps) • reliability (1-224) (higher the number, more reliable) • load (1-244) (higher the number, the more load carried) •sends updates every 90 seconds • maximum hop count is 255 (default 100) Perrine modified by Brierley 5/25/2017 Page 24 Cisco 2 - Routers OSPF Routing Protocol Chapter 4 Characteristics of OSPF: • link-state routing protocol • open standard • uses the SPF algorithm to calculate the lowest cost to a destination • routing updates are flooded as topology changes occur. Perrine modified by Brierley 5/25/2017 Page 25 Cisco 2 - Routers EIGRP Routing Protocol Chapter 4 Characteristics of EIGRP are: • distance-vector • Cisco proprietary • uses load balancing •uses a combination of distance vector & link-state features • use Diffused Update Algorithm (DUAL) to calculate the shortest path • updates broadcast every 90 seconds Perrine modified by Brierley 5/25/2017 Page 26 Cisco 2 - Routers BGP Routing Protocol Chapter 4 Characteristics of BGP are: • distance vector exterior routing protocol • used between ISP and clients • used to route internet traffic between AS (autonomous systems) Perrine modified by Brierley 5/25/2017 Page 27 Cisco 2 - Routers Configure routing protocols Chapter 4 RouterA#config t RouterA(config)# router <routing protocol> [AS number] RouterA(config-router)# network <networks on the routers interfaces> As an example: RouterA(config)# router rip RouterA(config-router)# network 192.16.10.0 As an example: RouterA(config)# router igrp 100 RouterA(config-router)# network 192.16.10.0 Perrine modified by Brierley 5/25/2017 Page 28 Cisco 2 - Routers Configure routing protocols Chapter 4 210.45.20.0 net s0 s1 192.10.10.0 net Router A e0 172.120.0.0 net RouterA# config t RouterA(config)# router rip RouterA(config-router)# network 192.10.10.0 RouterA(config-router)# network 172.120.0.0 RouterA(config-router)# network 210.45.20.0 Perrine modified by Brierley 5/25/2017 Page 29 Cisco 2 - Routers Border Gateways & Autonomous Systems Chapter 4 Autonomous systems have an identifying number, which is assigned to it by the American Registry of Internet Numbers (ARIN) or a provider. This autonomous system number is a 16-bit number. Perrine modified by Brierley 5/25/2017 Page 30 Cisco 2 - Routers Chapter 4 Module 6 Routing & Routing Protocols END Perrine modified by Brierley 5/25/2017 Page 31