Routing and Routing Protocols Module 6 Routing and Routing Protocols

Routing… Nothing more than directions for getting from one network to another. _________________________, for traffic going through a network cloud, occurs at the network layer A router makes decisions based upon the ________________________________ ___________________________________________________________________ routers must learn the direction to remote networks by either static or dynamic routing

Dynamic v. Static Routing _______________________________ ______________________________________________________________. Static routing is most often used with stub networks where only one path exists to the destination. _______________ ________________________________ Allows for increased security In STATIC routes, the administrator must manually update this static route entry whenever an internetwork topology change requires an update. static routes are insufficient for creating a large, reliable, network, they have several key roles to play: increased security, decreased amounts of dynamic routing data- so routing updating info about that path is not being broadcast to other routers. Only the net admin. Need know about static routing paths

Static route configuration using outgoing interface Interface on Hoboken router closet to destination network Going to… Mask of destination network

Static route configuration using next-hop IP address Serial IP address on ADJACENT router closet to destination network Going to… Mask of destination network

Difference in Configurations _______________ assigned to the route by the router (Hoboken) or network administrator as it is placed in the routing table. Admin. Distance- _____________________ ____________________________________________ Used as a means to find the best path ____________________________________________ Outgoing interface option Admin distance = 0 Next-hop IP address Admin distance = 1 Either of the commands will install a static route in the routing table of Hoboken. The only difference between the two is in the administrative distance assigned to the route by the router as it is placed in the routing table. Admin. Distance- used as a means to choose the path that will be taken

Static route cont… Customize the _________________ _______________ by adding it to the end of the “ip route” command waycross(config)#ip route 172.16.3.0 255.255.255.0 172.16.4.1 _______ If the router cannot reach the outgoing interface programmed ____________________________ ______________________________

Default Routes A _____________________________ _______________ that all routers on a network can send packets to if they __ ____________________________________________________________ The default route concept assumes that data forwarded along the default route will eventually encounter a router that DOES know the path to the destination. Default routes are one way for routers in large networks not to require knowledge of all routes. Essentially, if a default route is configured on 1 router, it assumes and trusts that the next router will have a best path to the destination, or yet another default route. Used strategically, default routes can greatly help data flow in a large network

Default route forwarding Special static route Command Issued in global config mode ip route _____________________ [next-hop-address | outgoing interface] Routers are typically configured with a default route for Internet-bound traffic, since it is often impractical and unnecessary to maintain routes to all networks in the Internet. Way to reach all networks not directly connected

Verification and troubleshooting “_________________________” used to verify that the static route has been entered correctly “__________________________” Used to verify that the route that was configured is in the _______________ What troubleshooting techniques can we use to verify connectivity via a static route? What troubleshooting techniques can we use to verify connectivity via a static route? Ping and traceroute

Dynamic v. Static Routing Dynamic routing refers to the process of _____________________________________________________________. Routing protocols enable dynamic routing where multiple paths to the same destination exist.

Routed v. Routing Protocols Routed (or Routable) protocols are protocols that ________________ __________________________________________________ using a hierarchical addressing scheme. Carry packaged data Operate at the ________________ Examples include ________________ ______________________________

Routed v. Routing Protocols A routing protocol ____________ __________________________________________________________. Routers use routing protocols to _______ ______________________. These maps allow ___________________________ ____________________. Maps become part of the router’s routing table. Allow routers to make decisions Examples of routing protocols include: _______________________________

Autonomous System (AS) Collection of networks _______________ _________________________ strategy. AS is viewed as a single entity ________________________ must be used between Autonomous systems Identified by a 16 bit number that _________ _________________ or can be assigned by the network administrator Some routing protocols required the use of an AS The AS may be run by one or more operators while presenting a consistent view of routing to the external world. Some routing protocols required the use of an AS such as IGRP

More on routing protocols Goal of a routing protocol is to ____ ____________________________. Contains the learned networks and associated ports for those networks ______________________________ _____________________________ _______________________________________________________

Routing table used for path determination and packet switching Example of a routing table This is the interface number, there could be any number of hosts on network 1.0 Switching function allows a router to accept a packet on one interface and forward it through a second interface. The path determination function enables the router to select the most appropriate interface for forwarding a packet Routing table used for path determination and packet switching

More on Dynamic routing Offers _______________________ Dynamic routing depends on : _______________________________________________________ ____________________________, to other routers  Routing protocols dictate how communication with neighbors takes place

Dynamic routing details cont… The best path to a destination, is determined by _______________ ____________________ called… A _______________________ _______________________________ The fewer the stop signs- the better Metrics calculated based on different __________________________ << ASK FIRST>> If you are traveling to Rochester- list some ways you can get there… Using a highway and/ or a postal delivery analogy; discuss with the students what criteria might make one path better than another. Then introduce hop count as the most basic metric

Characteristics used to generate the Metric ___________ - the data capacity of a link; delay ____________ - the amount of activity on a network resource such as a router or link reliability _______________ - the number of routers a packet must travel through before reaching its destination ticks ________________ - an arbitrary value assigned by a network administrator metrics most commonly used by routers are as follows: bandwidth - the data capacity of a link; (normally, a 10 Mbps Ethernet link is preferable to a 64 kbps leased line) delay - the length of time required to move a packet along each link from source to destination load - the amount of activity on a network resource such as a router or link reliability - usually refers to the error rate of each network link hop count - the number of routers a packet must travel through before reaching its destination ticks - the delay on a data link using IBM PC clock ticks (approximately 55 milliseconds). cost - an arbitrary value, usually based on bandwidth, monetary expense, or other measurement, that is assigned by a network administrator Talked about in book- not in the curriculum in chapter 6!!!

The more characteristic, more accuracy ALSO the more time it takes to come up with the metric (processor intensive) In this example, the metric is comprised of four different characteristics.

Convergence At the time of convergence __________ _______________________________________________________________ Every time there is a topology change, routing protocols _________________ ________________________________________________________________ The time of convergence varies depending upon the routing protocol being used. The _______________________________ Fast convergence is a desirable network feature because it reduces the period of time in which routers would continue to make incorrect/wasteful routing decisions. When all routers in an internetwork are operating with the same knowledge, the internetwork 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

Distance-vector Routing Determines the route based on the direction (vector) and distance to the destination Each router receives _____________ _____________________________________________________________________ Distance-vector protocols _____________ _____________________________________________________________________ Topology change updates proceed step-by-step from router to router as in the discovery process Most routing algorithms can be classified as one of two basic algorithms: distance vector; or  link state.  In Distance-vector- Router A learns about other networks based on the information that it receives from Router B. Each of the other network entries in the routing table has an accumulated distance vector to show how far away that network is in a given direction During the updating process, a router sends its entire routing table to each of its adjacent neighbors.

Distance Vector example A doesn’t directly receive D’s routing table, but receive the information via B who got the info from C – the directly connected neighbor

___________ seen in Distance Vector routing protocols ____________________________ Can cause Routing Loops Occurs when new updated information causes inconsistent routing entries. Router X Internet Cloud EXAMPLE ABOVE: Router X is unreachable via router 1, so the packet destined for router X is sent via router 2 Router 2’s metric shows the quicket way to get to Router X is thru Router 1 Routing loop ROUTING LOOPS IS AN FYI RIGHT NOW… MORE ON THIS NEXT CHAPTER

Link-state (SPF) Routing AKA “shortest path first” algorithm ___________________________________________________________________ Link-state protocols maintain complex __________________________________________________________________. Each time a new route is added or a route goes down, each router receives a message and then recalculates a spanning tree algorithm and updates its topology database. SPF - (shortest path first) algorithms A link-state routing algorithm maintains full knowledge of distant routers and how they interconnect. Whereas the distance-vector algorithm has nonspecific information about distant networks and no knowledge of distant routers

Link-state cont… ______________________ Link-state routing algorithm _______________ ____________________________________ Link-state advertisements (_________) ________________________________________________________________________. _________________________________ _________________________________ ______________________ The router that first becomes aware of a topology change forwards the information to _________________________________________________________________________ Triggered updates- updates occur only when needed Routers running link-state protocols require more memory and perform more processing than distance vector routing protocols. Routers must have sufficient memory to be able to hold all the information from the various databases, the topology tree, and the routing table When changes occur, the routers that first become aware of the change send information to other routers or to a designated router that all other routers refer to for updates GIVE AN EXAMPLE IN CLASS- SAY ONE STUDENT HOLDS ALL UPDATES- THEN EVERYONE ELSE KNOWS WHERE TO GO TO GET UPDATES OR AT LEAST CHECK FOR UPDATES

Disadvantages of Link-State Processing requirements _____________________________________________________________________________ Bandwidth Uses ____________________________________ _______________________________________ After initial flood, uses ____________________ __________________________________________ If LSA distribution to all routers is not done correctly, link-state routing ______________ __________________________________ For link-state routing, their memory must be able to hold information from various databases, the topology tree, and the routing table During the initial discovery process, all routers using link-state routing protocols send LSA packets to all other routers. This action floods the internetwork as routers make their en masse demand for bandwidth, and temporarily reduce the bandwidth available for routed traffic that carries user data. <<NEXT TIME TEACHING THIS, START WITH 11.4.5 AND ADD ANYMORE NEEDED SLIDES>>

Configuring Routing Example Autonomous system # required for IGRP, EIGRP Example GAD(config)#router igrp 2 GAD(config-router)#network 172.16.0.0 Global config mode Routing config mode The network numbers are based on the network class addresses, not subnet addresses or individual host addresses. Major network addresses are limited to Class A, B, and C network numbers Necessary to enable the routing process to determine which interfaces participate in the sending and receiving of routing updates. Network addresses only listed here- NOT subnets

What are the routing protocols? RIP ______________________________________________ ______________ is used as the metric for path selection. If the hop count is greater than ___, the packet is discarded. Routing ________________________________, by default. IGRP Cisco's ________________________________ ________________________________________ are used to create a composite metric. Routing _________________________________, by default. EIGRP Cisco’s ___________________________________________ Uses ______________________________. Uses a _________________________________________. Routing updates are broadcast every ____________ or as ________________________ changes. RIP-- Routing Information Protocol Hop count max is 15 IGRP --Interior Gateway Routing Protocol is a proprietary protocol developed by Cisco EIGRP– considered a hybrid protocol EIGRP uses distance-vector metrics. However, it uses event-triggered topology changes instead of periodic passing of routing tables Interior routing protocols are designed for use in a network whose parts are under the control of a single organization.

More routing protocols… OSPF A ____________________________ used to calculate the lowest cost to a destination. Routing ___________________________ as topology changes occur. BGP It is a ______________________________ ______________________________ Used ________________ or ISPs and clients. Used to route ________________________ ____________________________________ An exterior routing protocol is designed for use between two different networks that are under the control of two different organizations. OSPF -- Open Shortest Path First is a nonproprietary link-state routing protocol BGP-- Border Gateway Protocol is an exterior routing protocol For example, a company would run BGP, an exterior routing protocol, between one of its routers and a router inside an ISP

Summary comparison DISTANCE-VECTOR LINK-STATE Views network topology from neighbor’s perspective Gets common view of entire network topology Adds distance vectors from router to router Calculates the shortest path to other routers Frequent, periodic updates: slow convergence Event triggered updates: fast convergence Passes copies of routing tables to neighbors Passes link-state routing updates to all routers in the system.

Routing to another network When communicating with a destination on a different network, the data link frame uses the ___________________________________________________________________________________________________________________ At network layer, router examines the incoming packet's (IP) header to determine the destination network The __________________________________ ________________________________ THEN, the ______________________________ ______________________________________________________________________________ the host addresses the data link frame to the router, using the address of one of the router's interfaces

Configuring Static Routes Lab 6.1.6 One Lab for chapter 6 Configuring Static Routes Lab 6.1.6