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CN2668 Routers and Switches

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  1. CN2668Routers and Switches Kemtis Kunanuraksapong MSIS with Distinction MCTS, MCDST, MCP, A+

  2. Agenda • Chapter 8: Advanced Routing Protocols • Exercise • Quiz

  3. ClassfulRouting Protocols • Summarize networks to their major network boundaries (Class A, B, or C) • Do not carry subnet mask information in their routing table updates • Cannot be used • Networks with discontiguous subnets • Networks using VLSM • Examples: RIPv1 and IGRP

  4. ClassfulRouting Protocols (Cont)

  5. Classful Routing Protocols (Cont) • Figure 8-3 on Page 202 shows that RIP on RouterA is set to S0/0 and f0/0 • In the same time, an update from RouterC to RouterBmake RouterB thought that there is load balancing as shown in Figure 8-5 on Page 203 • Hence, the ping results are 50% as shown in Figure 8-6 on Page 204

  6. Classless Routing Protocols • Allow dynamic routing in discontiguous networks • Carry subnet mask information in the routing table updates • See Figure 8-7 on Page 204 • Examples: RIPv2, EIGRP, OSPF, and BGP

  7. Classless Routing Protocols • Version 2 • To switchs RIP to version 2 • No Auto-summary • To overrides default behavior of summarizing to major network boundaries • As shown in Figure 8-9 and 8-10 on Page 205

  8. Routing Information Protocol version 2 • RIPv2 is a set of extensions to RIPv1 • A distance-vector routing protocol • Supports a maximum of 15 hops • The major change is RIPv2’s ability to carry subnet mask information • RIPv2 multicasts its updates using the multicast address of 224.0.0.9

  9. RIPv2 (Continue)

  10. RIPv2 (Continue) • Cisco routers can be configured on a per-interface basis • See Figure 8-14 on Page 207 • If the interface has not set to send/receive version 1, the packet will be drop • See Figure 8-15 on Page 208

  11. RIPv2 (Continue) • To authenticate routing peers • Both ends has to use RIPv2 • Configuring RIPv2 authentication requires the following steps: • Define a key chain • Define keys in the key chain • Enable authentication on the interface by specifying the key chain to be used • Enable either clear text or MD5 authentication • Manage the keys (optional key lifetimes)

  12. Enhanced Interior Gateway Routing Protocol • Enhanced Interior Gateway Routing Protocol (EIGRP) • A Cisco proprietary classless protocol designed to overcome the limitations found in IGRP • Distance-vector routing protocol • Protocol Dependent Modules (PDMs) • Allow EIGRP to carry multiple routed protocols within their own native packet formats

  13. EIGRP (Continued) • EIGRP uses nonperiodic, partial, and bounded routing table updates • Update only when there is changed • Update only what is changed • Update to only the party affected

  14. EIGRP (Continued) • EIGRP makes use of a composite metric comprised of six different factors: • Hops, Load, Bandwidth, Reliability, Delay, MTU • By default, the formula used for metric calculation in EIGRP is: Metric = [(K1*Bandwidth + (K2*Bandwidth)/(256-load) + K3*Delay)*K5/(reliability + K4)]*256 • NOTE: K1 = 1, K2 = 0, K3 =1, K4 = 0, K5 =0

  15. EIGRP Components • Protocol Dependent Modules (PDM) • Allow EIGRP to support multiple Network layer routed protocols such as IP, IPX, and AppleTalk • Neighbor discovery and maintenance • Allow EIGRP to discover neighbors and keep track of their status

  16. EIGRP Components (Continued) • Reliable Transport Protocol (RTP) • Routing table updates are an example of an EIGRP packet type that uses reliable multicast via RTP • See Table 8-1 on Page 214 for types of packet • Diffusing Update Algorithm (DUAL) • Allows EIGRP to quickly recover from a link outage and route around network problems

  17. EIGRP Components (Continued) • Key terms associated with DUAL • Successor • the best route to a destination • Feasible distance (FD) • the lowest metric to a destination • Reported distance (RD) • the distance a router advertises to a network

  18. EIGRP Components (Continued) • Key terms associated with DUAL • Feasible successor • a backup route to the successor route • Feasibility condition • Used to ensure that a backup route does not contains a loop • Adjacency • A relationship formed between EIGRP neighbors

  19. EIGRP Components (Continued) • Show ipeigrp topology all-links • To show the entire topology table as show in figure 8-25 on Page 217 • If the status is P or Passive, that means everything is good • The status A or Active could cause from hardware errors or configuration errors

  20. EIGRP Configuration • EIGRP is classless, but it summarizes to classful network boundaries by default • The no auto-summary command turns off this default behavior • Router eigrp [process-id] • Process-id has to be same on two routers for them to share EIGRP routes • See Figure 8-26 on Page 218 on command summary • the bandwidth command to set the actual bandwidth on serial links to prevent auto selection

  21. EIGRP Configuration (Continued) • EIGRP supports optional authentication of routing peers • Configuring EIGRP authentication requires the following steps: • Define a key chain • Define keys in the key chain • Enable authentication on the interface by specifying the key chain to be used • Manage the keys (optional key lifetimes)

  22. Open Shortest Path First • An open standards, link-state routing protocol that supports classless routing, VLSM, and authentication • Link-state routing protocols allow routers to share a common view of the entire network • Each router sends out link-state advertisements (LSAs) describing its attached links to all routers in an area • Each router needs to hold a topological database of the entire area

  23. OSPF (Continued) • OSPF is ideally suited for large networks • Uses a concept known as areas to bound link-state advertisements • An area is the portion of a network within which LSAs are contained • All OSPF routers configured with the same area identification will accept LSAs from one another • See Figure 8-29 on Page 221

  24. OSPF Concepts • Link • A router’s interface • Link-state • The status of a link on a router • Area • Defines the confines within which LSAs are contained • Cost • The default metric for OSPF

  25. OSPF Concepts (Continued) • Cost • Bandwidth [speed in Kb] • See Table 8-3 on Page 222 for default cost • Reference-bandwidth for OSPF is Fast Ethernet or 100 Mbps • Any link 100 Mbps or faster has a cost of 1 • See Figure 8-30 on Page 222 • If you change the reference-bandwidth, you have to change on all routers

  26. OSPF Concepts (Continued) • Adjacencies database • Contains information about all OSPF peers with which a router has successfully exchanged Hello packets • Hello-interval and dead-interval must match on all routers for them to form the neighbor table • Topological database • Holds the common view of the network formed from the link-state advertisements that are received

  27. OSPF Concepts (Continued) • Designated routers (DRs) • On broadcast, multiaccess networks, OSPF elects a DR, which acts as a central point for LSAs • On multiaccess networks such as Ethernet, OSPF elects a DR and establish adjacencies with the DR only • Backup designated routers (BDRs) • It takes over if the DR fails

  28. OSPF Concepts (Continued) • The election occurs via Hello process • The id can be one of three things • Highest IP address configured on a loopback interface • Highest IP address on an active physical interface • ID Set using the ospf router-id [ipaddress]

  29. OSPF Operation • Steps • An OSPF router forms adjacencies with neighbors • A DR and BDR are elected in OSPF • Routers will flood their link-state advertisements and go through the process of selecting the best route to each network • OSPF uses Dijkstra’s Shortest Path First algorithmto find the best path • Each router sees itself as the central point from which a loop-free, best-cost path to each network is determined

  30. Single-Area OSPF Configuration

  31. Single-Area OSPF Configuration • Require two key commands • Router ospf [process id] • Network command use a wildcard number • Network 172.20.0.0 0.0.255.255 area 0 • Default-information originate • Allows injection of a default route • Must run on a border router • RouterB in Figure 8-29 on Page 221

  32. OSPF Authentication • OSPF provides authentication of routing table updates via several methods • No authentication (the default) • Authentication with passwords sent in clear text • Authentication using MD5 hashing of a shared secret key

  33. OSPF Authentication (Continued) • To perform MD5 authentication of routing updates in OSPF, two steps must be completed: • Configuration of authentication keys on each OSPF interface • See Figure 8-39 on Page 228 • Configuration of area authentication • See Figure 8-40 on Page 229

  34. Controlling Route Traffic • passive-interface command • An important entry-level command for controlling route traffic • Disrupts the function of EIGRP and OSPF • The command causes a router to listen only on the passive interface • Therefore, if used with EIGRP or OSPF, the router will not send Hellos out the interface • The result is a link that is seen as having no neighbors on it • Therefore, it will not be used to form adjacencies

  35. Controlling Route Traffic (continued)

  36. Assignment • Review Questions • Lab • 8.2 – 8.4