© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 1 Version 4.0 Routing with a Distance Vector Protocol in an Enterprise Network Introducing.

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 1 Version 4.0 Routing with a Distance Vector Protocol in an Enterprise Network Introducing Routing and Switching in the Enterprise – Chapter 5

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 2 Objectives  Compare and contrast a flat network and a hierarchical routed topology.  Configure a network using RIP.  Describe and plan a network using EIGRP.  Design and configure a network using EIGRP.

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 3 Critical Data 1.Crucial information and services typically reside near the top of the hierarchy, in secured server farms or on Storage Area Networks (SANs). 2.Communication between different levels of the hierarchy requires a combination of LAN and WAN technologies. 3.A star topology provides centralized control of the network, but results in a single point of failure. 4.Mesh topologies eliminate the single point of failure, but decentralize control and can increase cost. 5.A routing table is a data file that exists in RAM and stores information about directly connected and remote networks.

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 4 Critical Data 6.A static route includes the network address and subnet mask of the destination network, along with the exit interface or the IP address of the next-hop router. 7.Dynamic routing protocols enable routers to share information about the reachability and status of remote networks through network discovery. 8.Limiting traffic to a single point of entrance or exit creates a stub network. 9.In an enterprise network, static routes configured with exit interfaces are ideal for point-to-point connections like those between a border router and the ISP. 10.A special type of static route called a default route specifies a gateway to use when the routing table does not contain a path to a destination.

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 5 Compare and Contrast a Flat Network and a Hierarchical Routed Topology  Enterprise hierarchy  Combination of LAN and WAN technologies  DMZ (e-commerce)

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 6 Compare and Contrast a Flat Network and a Hierarchical Routed Topology Traffic control design  Redundant links  QoS  Packet filtering ROUTERS forward traffic and prevent broadcasts from clogging the main channels to crucial services control the flow of traffic between LANs, allowing only the required traffic to pass

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 7 Compare and Contrast a Flat Network and a Hierarchical Routed Topology  Star and extended star topologies provides centralized control of the network scalable  Mesh topologies Partial mesh Full mesh

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 8  Building the routing table Exit interface or next hop associates each network with either an exit int or next hop Administrative distance attaches a number to each route that represents the trustworthiness or accuracy of the source of the routing information

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 9  Directly connected routes - attaches to a router interface  Static routes - manually configured  Dynamic routes - share information about the reachability and status of remote networks through network discovery

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 11 Compare and Contrast a Flat Network and a Hierarchical Routed Topology  Advantages of static routing Stub networks Security Lower overhead

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 13 Static routes configured with a next hop interface require two steps to determine the exit interface (recursive lookup) In a recursive lookup: The router matches the destination IP address of a packet to the static route Matches the next hop IP address of the static route to entries in its routing table to determine which interface to use

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 14 Compare and Contrast a Flat Network and a Hierarchical Routed Topology  Summary static routes  Floating static routes Higher administrative distance than the route learned from a dynamic routing protocol Does not display in the routing table unless dynamic fails

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 15  Default routes specifies a gateway to use when the routing table does not contain a path to a destination.  Gateway of last resort final default route, located on the border router, sends the traffic to the ISP

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 16 Routing Using the RIP Protocol  Characteristics of distance vector protocols share network information with directly connected neighbors - neighbor routers then advertise the information to their neighbors  Hop count metric

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 17 Routing Using the RIP Protocol  Characteristics of RIPv1 Automatically summarizes at classful boundary Does not send subnet mask information in the update Broadcasts routing updates every 30 seconds

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 18 Routing Using the RIP Protocol  Characteristics of RIPv1 Does not support VLSM and CIDR A router configured with RIPv1 either uses the subnet mask configured on a local interface, or applies the default subnet mask Due to this limitation, the subnets of the networks that RIPv1 advertises should not be discontiguous if correct routing is to occur.

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 19 Routing Using the RIP Protocol  RIPv2 configuration supports VLSM and CIDR subnet mask field is included in v2 updates (allows the use of discontiguous networks) ability to turn off automatic summarization of routes multicasts its updates to 224.0.0.9 has an authentication mechanism

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 20 Routing Using the RIP Protocol  RIPv2 shares many of the features found in RIPv1, such as:  Hop-count metric  15-hop maximum  TTL equals 16 hops  Default 30-second update interval  Route poisoning, poisoned reverse, split horizon, and holddowns to avoid loops  Administrative distance of 120

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 24 Routing Using the RIP Protocol Problem Discontiguous subnets Unnecessary traffic Routing loops Solution No auto-summary Passive-interface (disables routing updates on specified interfaces) Poisoned reverse, split horizon, holddown timer, triggered updates Problems with RIP and their solutions:

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 25 Routing Using the RIP Protocol Poisoned reverse - sets the metric for a route to 16, making it unreachable Split horizon - dictates that a router receiving routing information on an interface cannot send an update about that same network back out the same interface Holddown timer - refuses to accept route updates with a higher metric to the same destination network for a period after a route goes down Triggered updates - when a route fails, RIP does not wait for the next periodic update Problems with RIP and their solutions:

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 27 Routing Using the RIP Protocol  show ip protocols  show ip route  show ip rip database (Lists all the routes known by RIP)  debug ip rip or debug ip rip {events} (Displays RIP routing updates as sent and received in real time)

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 30 Describe and Plan a Network Using EIGRP  Compare EIGRP and RIP Instead of sending periodic routing updates, EIGRP sends small hello packets to maintain knowledge of its neighbors. EIGRP multicasts partial updates about specific changes to only those routers that need the information, not to all routers in the area.

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 32 Describe and Plan a Network Using EIGRP  Characteristics of EIGRP Composite metric Guaranteed loop-free operation Bounded updates Hello packets

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 34 Describe and Plan a Network Using EIGRP  Neighbor table - lists information about directly connected neighbor routers  Topology table - lists all routes learned from each EIGRP neighbor (successor and feasible – 5.3.3.2)  Routing table - displays only the best paths called the successor routes

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 36 Describe and Plan a Network Using EIGRP  EIGRP neighbors and adjacencies  Hello protocol - By default, hello packets are multicast every 5 seconds on links greater than a T1 and every 60 seconds on T1 or slower links.

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 37 Describe and Plan a Network Using EIGRP  EIGRP packet types Whenever DUAL places a route in the active state, the router must send a query packet to each neighbor. Neighbors must send replies, even if the reply states that no information on the destination is available. The information contained in each reply packet helps DUAL to locate a successor route to the destination network. Queries can be multicast or unicast. Replies are always unicast.

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 38 Describe and Plan a Network Using EIGRP  RTP: Reliable Transport Protocol - guarantees delivery and receipt of EIGRP packets for all Network Layer protocols  PDM: Protocol Dependent Module - a router running IP, IPX, and AppleTalk has three neighbor tables, three topology tables, and three routing tables.

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 39 Describe and Plan a Network Using EIGRP  EIGRP metrics and convergence – Bandwidth, Delay, Reliability, Load  K values  Feasible and reported distance Feasible distance is the best EIGRP metric along the path to the destination from the router. Advertised distance is the best metric reported by a neighbor.

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 41 Design and Configure a Network Using EIGRP  Basic EIGRP configuration  Wildcard masks  Logging neighbor changes  Bandwidth  Load balancing NOTE: The AS number in the command must match on all routers that work within the EIGRP routing process.

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 42  EIGRP summarization  Parent and child routes - The summary route is called the parent route and the subnet routes are called the child routes.  Null0 interface - Indicates that this is not an actual path, but a summary for advertising purposes  Manual summarization - no auto-summary

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 44 EIGRP  show ip protocols Verifies that EIGRP is advertising the correct networks Displays the autonomous system number and administrative distance  show ip route Verifies that the EIGRP routes are in the routing table Designates EIGRP routes with a D or a D EX Has a default administrative distance of 90 for internal routes  show ip eigrp neighbors detail Verifies the adjacencies EIGRP forms Displays the IP addresses and interfaces of neighbor routers

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 45 EIGRP  show ip eigrp topology Displays successors and all feasible successors Displays feasible distance and reported distance  show ip eigrp interfaces detail Verifies the interfaces using EIGRP  show ip eigrp traffic Displays the number and types of EIGRP packets sent and received

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 47 Summary  Enterprise networks are hierarchical  Networks use static and dynamic routing to move information  Dynamic routing protocols are classified as either distance vector or link state  RIP is a distance vector routing protocol  EIGRP is a Cisco proprietary distance vector routing protocol with many advanced features  EIGRP works best if its default features are modified to suit the routing situation

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 48  Does not work in a multi-vendor environment because it is a Cisco proprietary protocol  Works best with a flat network design  Must share the same autonomous system among routers and cannot be subdivided into groups  Can create very large routing tables, which requires large update packets and large amounts of bandwidth  Uses more memory and processor power than RIP  Works inefficiently when left on the default settings  Requires administrators with advanced technical knowledge of the protocol and the network

© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 1 Version 4.0 Routing with a Distance Vector Protocol in an Enterprise Network Introducing.

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© 2006 Cisco Systems, Inc. All rights reserved.Cisco Public 1 Version 4.0 Routing with a Distance Vector Protocol in an Enterprise Network Introducing.

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