CN2668 Routers and Switches Kemtis Kunanuraksapong MSIS with Distinction MCTS, MCDST, MCP, A+ Agenda • Chapter 8: Advanced Routing Protocols • Exercise • Quiz Classful Routing 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 Classful Routing Protocols (Cont) 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 RouterB make 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 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 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 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 RIPv2 (Continue) RIPv2 (Continue) • Cisco routers can be configured on a perinterface 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 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) 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 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 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 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 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 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 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 EIGRP Components (Continued) • Show ip eigrp 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 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 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) 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 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 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 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 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 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 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] 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 algorithm to 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 Single-Area OSPF Configuration 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 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 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 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 Controlling Route Traffic (continued) Assignment • Review Questions • Lab ▫ 8.2 – 8.4