Chapter 3 Dynamic Routing Protocols Routing Protocols and Concepts quangkien@gmail.com 2 Topics  Introduction to Dynamic Routing Protocols  Perspective and Background  Network Discovery and Routing Table Maintenance  Dynamic Routing Protocol Advantages  Classifying Dynamic Routing Protocols  IGP and EGP  Distance Vector and Link- State  Classful and Classless  Convergence  Metrics  Purpose of the Metric  Metrics and Routing Protocols  Load Balancing  Administrative Distance  Purpose of Administrative Distance  Dynamic Routing Protocols and Administrative Distance  Static Routes and Administrative Distance  Directly Connected Networks and Administrative Distance Introduction to Dynamic Routing Protocols  Perspective and Background  Network Discovery and Routing Table Maintenance  Dynamic Routing Protocol Advantages 4 Perspective and Background  Dynamic routing protocols have evolved over several years  As networks have evolved and become more complex, new routing protocols have emerged.  Most institutions have migrated to new protocols, others are still in use.  The first version of RIP was released in 1982, but some of the basic algorithms within the protocol were used on the ARPANET as early as 1969. 5 Perspective and Background Interior Routing Protocols or Interior Gateway Protocols (IGP)  Distance Vector  RIPv1 – Simple, Classful, limited metrics (hop count)  RIPv2 – Simple, Classless, limited metrics (hop count) Cisco Proprietary  IGRP – Simple, Classful, better metric (BW, delay, reliab., load)  EIGRP – Simple, Classless, same metric, DUAL (backup routes)  Link State  OSPF – Perceived complex, classless, Cisco metric BW, IETF  IS-IS - Perceived complex, classless, metric “default”, ISO  Classful (does not support CIDR and VLSM)  Classless (supports CIDR and VSLM) 6 Perspective and Background Exterior Routing Protocols or Exterior Gateway Protocols (EGP)  Border Gateway Protocol (BGP) is now used between Internet service providers (ISP) as well as between ISPs and their larger private clients to exchange routing information.  Path Vector routing protocol, metric – attributes (policies)  Replaced EGP 7 Role of Dynamic Routing Protocol  Dynamic Routing Protocols:  Exchange of routing information between routers  Dynamically learn information about remote networks  Determines the best path to each network  Adds routes to routing tables  Automatically learn about new networks  Automatically finds alternate paths if needed (link failure in current path) 8 Role of Dynamic Routing Protocol  Compared to Static Routes:  Advantages of Dynamic Routing Protocols:  Less administrative overhead (change modifications)  Disadvantage of Dynamic Routing Protocols  More CPU and memory requirements  This is not that big an issue in most networks and with modern routers.  Configuration is less error-prone  Scales better with larger networks  “Less secure” if routing updates are sent unencrypted.  Most networks use both dynamic and static routes 9 Purpose of Dynamic Routing Protocols  A routing protocol is a set of processes, algorithms, and messages that are used to exchange routing information and populate the routing table with the routing protocol’s choice of best paths.  Purpose:  Discovering remote networks  Maintaining up-to-date routing information  Choosing the best path to destination networks  Having the ability to find a new best path if the current path is no longer available  Components of a routing protocol (depending upon the routing protocol):  Data structures: Tables or databases for their operations, kept in RAM.  Algorithm:  An algorithm is a finite list of steps used in accomplishing a task.  Routing protocols use algorithms for processing routing information and for best-path determination.  Routing protocol messages:  Discover neighboring routers  Exchange routing information  Learn and maintain accurate information about the network 10 Dynamic Routing Protocol Operation The operations of a dynamic routing protocol vary depending on the type of routing protocol, but in general: 1. The router sends and receives routing messages on its interfaces. 2. The router shares routing messages and routing information with other routers that are using the same routing protocol. 3. Routers exchange routing information to learn about remote networks. 4. When a router detects a topology change, the routing protocol can advertise this change to other routers. [...]... link-state routing protocol Fast convergence of the network is crucial More in later chapters 21 Classful and Classless Routing Protocols All routing protocols can also be classified as either Classful routing protocols Classless routing protocols IPv6 routing protocols are classless 22 Classful Routing Protocols Classful routing protocols do not send subnet mask information in routing updates The first routing. .. Exterior routing protocols 14 IGP and EGP Interior gateway protocols (IGP): Used for intra-autonomous system routing Routing inside an autonomous system Exterior gateway protocols (EGP): Used for inter-autonomous system routing Routing between autonomous systems 15 Distance Vector and Link-State Routing Protocols Interior gateway protocols (IGP) can be classified as two types: Distance vector routing protocols. .. not support VLSM and CIDR All subnets within the same “major classful network address” must have the same mask Other limitations to classful routing protocols, including: Inability to support discontiguous networks (later) More later! 24 Classless routing Protocols 172.16.0.0/16 Major Classful Network /27 and /30 subnets 172.16.128.0 /30 172.16. 132 .0 /30 172.16. 136 .0 /30 Classless routing protocols include...Static Routing Usage, Advantages, and Disadvantages Primary uses: Smaller networks that are not expected to grow significantly Routing to and from stub networks Default route 11 Classifying Dynamic Routing Protocols IGP and EGP Distance Vector and Link-State Classful and Classless Convergence Classifying Routing Protocols Routing Protocols can be classified by: IGP or... Dynamic Routing Protocols and Convergence R2’s Routing Table R1’s Routing Table R3’s Routing Table Generally, convergence time: Slow: RIP and IGRP Faster: EIGRP, OSPF, and IS-IS 27 Metrics Purpose of the Metric Metrics and Routing Protocols Load Balancing Purpose of a Metric ? Metrics are a way to measure or compare Determine which route is the best path Assign costs to reach remote networks Routing. .. the network address in routing updates Today’s networks are no longer allocated based on classes Subnet mask cannot be determined by the value of the first octet Classless routing protocols are required in most networks today because of their support for: VLSM CIDR Discontiguous networks 25 Dynamic Routing Protocols and Convergence R2’s Routing Table R1’s Routing Table R3’s Routing Table An important... updates The first routing protocols, such as RIP When network addresses were allocated based on classes Class A, B, or C Routing protocol did not need to include the subnet mask in the routing update Network mask determined based on value of first octet of the network address 23 Classful Routing Protocols 172.16.0.0/16 Major Classful Network All /24 subnets Classful routing protocols do not include... classless 13 IGP and EGP An autonomous system (AS)—otherwise known as a routing domain—is a collection of routers under a common administration sharing a common routing strategy Each AS has a 16 bit autonomous system number Company’s internal network An ISP’s network Because the Internet is based on the autonomous system concept, two types of routing protocols are required: Interior routing protocols. .. Metric Routing protocol metrics: RIP: Hop count IGRP and EIGRP: Bandwidth, delay, reliability and load OSPF (Cisco’s version): Bandwidth IS-IS: Four values (Cisco uses “default”) – Covered in CCNP BGP: Attributes – Covered in CCNP More later 30 Metric Parameters 56 Kbps R1 to reach the 172.16.1.0/24 network RIP: Fewest number of hops via R2 OSPF: Path with the highest cumulative bandwidth through R3 This... Path with the highest cumulative bandwidth through R3 This results in faster packet delivery 31 Metric Field in the Routing Table The routing table displays the metric for each dynamic and static route Static routes always have a metric of 0 Routing protocols install route in routing table with the lowest metric 32 R2# show ip route Gateway of last resort is not set R 192.168.1.0/24 [120/1] . Dynamic Routing Protocols  IGP and EGP  Distance Vector and Link-State  Classful and Classless  Convergence 13 Classifying Routing Protocols  Routing Protocols. Chapter 3 Dynamic Routing Protocols Routing Protocols and Concepts quangkien@gmail.com 2 Topics  Introduction to Dynamic Routing Protocols 