Rip and OSPF assignment (RIP ба OSPF дасгал ажил)

Departamento de Informática Escola de Engenharia

Universidade do Minho

_________________________________________________________________________Tecnologias e Protocolos de Rede, 2015/2016

Tecnologias e Protocolos de Rede [2015/2016] MIEI/MERSTel

Laboratory Work TP1: Routing [Part #1]

Objectives

• Develop initial/basic experiences in the configuration of OSPF and RIP routing protocols.

• Contact with real systems for programming/configuration of network equipment • Use of network emulation tools, e.g. CORE (Common Open Research Emulator) • Development of research skills and (self)learning processes related with the

configuration of routing protocols. Report

• All working groups will prepare a report describing the answers/ commands/tasks/analysis made in the context of this laboratory work. • The definition of the report structure and included contents is the responsibility of the working groups. • The reports will be evaluated taking into account i) the correction/technical quality of the solutions/settings/answers/explanations made regarding the proposed tasks/challenges and ii) clarity/organization/quality of the submitted report. • The reports should be submitted by the deadline set by the teacher.

____________________________________________________________________________ In the context of this work, it is expected that students perform the adequate research for the addressed topics. The following references/links are merely illustrative and should be complemented with other references deemed relevant.

• http://www.nrl.navy.mil/itd/ncs/products/core • http://downloads.pf.itd.nrl.navy.mil/core/vmware-image/ • Several manuals/documentation regarding the configuration of routing protocols in

CISCO equipment can be searched on the net, with many available in http://www.cisco.com/........ [note: In the CORE emulator the routing processes are based on the Quagga framework (http://www.nongnu.org/quagga/). However, most of the configuration commands are quite similar to the ones commonly used in CISCO IOSs]

____________________________________________________________________________ Tasks

- Familiarization with the emulator CORE (Common Open Research Emulator) http://www.nrl.navy.mil/itd/ncs/products/core




- Installation of the virtual machine of vcore 4.6 (available for VMware or VirtualBox) http://downloads.pf.itd.nrl.navy.mil/core/vmware-image/

A) RIP (Routing Information Protocol) Protocol

1. Define a network topology involving multiple routers, interconnecting core links and end-user networks. The topology should include at least two distinct redundancy scenarios: i) in the view of at least one of the routers there are at least two alternatives paths with the same minimum cost to a given network (e.g. “router x” to reach the network “rede A”) and ii) in view of at least one of the routers there are at least two paths with different costs to reach one or more networks (e.g. “router y” to reach the network “rede B”). Figure 1 shows an illustrative topology defined in this context.

Figure 1 – Illustrative example of a topology with multiple links and routers.

2. Analyse and comment on the IP address configuration of the routers/hosts interfaces that

was assigned by CORE.

3. Configure all routers of the topology to use the RIP protocol for routing dissemination of all interconnection and end-user networks.

4. Activate the defined topology and undertake connectivity tests (e.g ping etc.) between the

various routers/networks and check the used routes.

5. i) View and analyze the routing tables that were established by the routers of the core network.

[note: a specific routing table considered relevant for this purpose should be selected and explained in detail]

ii) View and analyze the routing tables of the hosts of the user-networks. [note: explain in detail a specific routing table of one of the hosts]




6. Assume that the administrator wants to change the time interval by which are generated

the RIP updates messages. What command could be used for this purpose?

7. Through the configuration console of the routers shutdown one (or more) interconnection links/interfaces in order to originate two distinct scenarios:

i) Even with the disabled interface(s) all routers/networks of the topology can

maintain connectivity ii) Some of the routers/networks have no available paths to reach other routers/

networks of the topology.

For each of the scenarios described above explain the observed modifications in the routing tables of the routers and comment on the time taken to propagate the routing information. [note: for each one of the above situations, a specific routing table considered relevant for this purpose should be also selected and explained in detail]

8. Configure one of the routers of the topology so that the traffic that it transmits to a particular destination network not cross the path with the smaller number of hops, but another alternative path (i.e. in the example in Figure 1, to send traffic to “rede B” the “router y” will use the path that passes through the “router x. For all other destinations the path with the least number of hops will continue to be the chosen one). [hint: in the theoretical lectures a specific command that solves this issue was mentioned]

9. Assume that your network will be connected to another external network via router x (see

Figure 2). Present and explain the configuration command(s) that will be used to assure that all traffic directed to external networks leave the domain using the router x.

Figura 2 – Router x as the exit point for all the external traffic.




B) OSPF (Open Shortest Path First) Protocol

10. In the defined topology configure some of the links with a bandwidth of 10 Mbps and others with a bandwidth 100 Mbps.

11. Configure all routers of topology to use the OSPF protocol for routing dissemination of all

interconnection and end-user networks. All routers should integrate a single OSPF area (e.g. area 0).

12. Activate the defined topology and undertake connectivity tests (e.g ping etc.) between the

various routers/networks and check the used routes.

13. Explain the OSPF configuration settings that were installed in the routers of the network.

14. View and analyze the routing tables that were established by the routers of the core network.

[note: a specific routing table considered relevant for this purpose should be selected and explained in detail]

15. What command allows you to check which OSPF costs are associated with the various

interfaces of a router? Analyze and comment the costs that were assigned to the links of the network topology.

16. Change the OSPF costs of the router interfaces so that links having bandwidths of 10 Mbps are assigned with a cost value of "10" and 100 Mbps links have OSPF cost values of "1".

17. In view of the change made in task 16 observe and analyze the changes that were made

in the routing tables of the routers. [note: a specific routing table considered relevant for this purpose should also be selected and explained in detail]

18. Taking into account the previous experiences explain how should be configured the

OSPF costs of the routers interfaces of a network topology.

19. In the previous experiments it can be observed that sometimes for the same destination multiple OSPF equal cost routes exist. (note: if you have not seen any of these cases proceed to configuration changes that create equal cost routes to a destination).

Investigate and explain different types of approaches that routers may use to deal with these situations. Also mention and explain the advantages/disadvantages of each one.

20. Suppose that the network routers of the defined topology have simultaneously the RIP and OSPF protocols activated. In this case, which routes would be chosen? Replicate this scenario in your network topology. (Note: if exist, delete all RIP/OSPF route redistribution commands form the routers configurations).

University of MinhoTechnologies and Network Protocols

RoutingBasic experiences with RIP and OSPF routing protocols

João DiasKhunbish Nyamsuren

Simão Dias

Contents

1 Introdução 3

2 Used Software and Method 3

3 RIP 43.1 Question 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43.2 Question 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53.3 Question 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63.4 Question 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73.5 Question 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73.6 Question 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93.7 Question 7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93.8 Question 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103.9 Question 9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

List of Figures

1 Topology 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 Enabling RIP protocol . . . . . . . . . . . . . . . . . . . . . . . . . 63 Connection path between R1 and PC-C2 . . . . . . . . . . . . . . . . . . 104 Confirmation that both of R2’s interfaces are shutdown. . . . . . . . . 115 Traceroute from R5 to the external host . . . . . . . . . . . . . . . . 126 Traceroute from R3 to the external host . . . . . . . . . . . . . . . . 127 Traceroute from R1 to the external host . . . . . . . . . . . . . . . . 138 Ping from PC-B1 to the external host . . . . . . . . . . . . . . . . . . 139 Ping from PC-C1 to the external host . . . . . . . . . . . . . . . . . . 14

AbstractIn dynamic routing environments, IP routing information is propagated using rout-

ing protocols. Nowadays, the most common protocols found in intranets are RoutingInformation Protocol and Open Shortest Path First. With the assistance of networkemulation software and with a set of predefined questions, we will go more in depthon the programming/configuration of network equipment that operates under the pre-viously mentioned protocols. After this project we were able to reach a betterunderstanding of this protocols and of the process that is required to accomplish afully operating network.

2

Introdução

A computer network is a network with two or more interconnected devices in such waythat they are able to exchange hardware or software resources. A network is composedof Nodes (which represents the devices) and links between them (which may be othernetworks).Nowadays we find networks at the most various places with the most diverse devices,this networks can be defined by their size, topology, physical layout and protocols.In this project we focus on the protocols, specifically two of the most common intranetprotocols: RIP (Routing Information Protocol) and OSPF(Open Shortest Path First).Network protocols are responsible for the routing process, specifying how devicescommunicate with each other by spreading information that enables them to select thebest routes between two nodes of a network.This document will be divided in two parts, one for RIP and another for OSPF. Eachpart will answer a series of questions as well as showing the used procedure to obtainsaid answers.

Used Software and Method

To be able to answer the provided questions, the workgroup used Common Open ResearchEmulator (CORE). Running under a virtual machine, this piece of software offers agraphical interface to build emulated networks.It allows us to represent different devices such as hosts, routers, switches and linksbetween them. Once the emulation is launched, a virtual machine will run to representeach node from which we have access to the bash shell where we can run the alreadyknown commands such as pings, traceroutes or even enter in the configuration mode.Most importantly, it allows us to swiftly change between protocols.

3

RIP

The Routing Information Protocol is a distance-vector protocol, therefore he is onlyaware of his neighbors and calculates the best path with this knowledge.

Question 1

Define a network topology involving multiple routers, interconnecting core links andend-user networks. The topology should include at least two distinct redundancy sce-narios:

1. In the view of at least one of the routers there are at least two alternativespaths with the same minimum cost to a given network (e.g. “router x” to reach thenetwork “rede A”)

2. in view of at least one of the routers there are at least two paths with differentcosts to reach one or more networks (e.g. “router y” to reach the network “redeB”). Figure 1 shows an illustrative topology defined in this context.)

Respecting this restrictions we developed the following topology:

Figure 1: Topology 1

Item 1 Proof

If we take in consideration R2, it has two possible ways to reach network 10.0.4.0/24with the same Hop cost: R2 -> R3 -> R5 or R2 -> R1 -> R4.Considering the Hop cost is the same, the protocol randomly chose to go throughthe first mentioned path. In the red line below, we can see that R2 can reach10.0.4.0/24 with 3 hops via interface eth1 wich leades to R3.

4

R>* 10.0.0.0/24 [120/2] via 10.0.1.1, eth0, 00:07:42C>* 10.0.1.0/24 is directly connected, eth0R>* 10.0.2.0/24 [120/2] via 10.0.1.1, eth0, 00:07:42C>* 10.0.3.0/24 is directly connected, eth1R>* 10.0.4.0/24 [120/3] via 10.0.3.2, eth1, 00:07:41R>* 10.0.5.0/24 [120/2] via 10.0.3.2, eth1, 00:07:41R>* 10.0.6.0/24 [120/2] via 10.0.3.2, eth1, 00:07:41C>* 127.0.0.0/8 is directly connected, lo

Now if we shutdown R2’s eth1 interface, R2’s routing table is forced to changeand we can see that the second alternative path is selected. In the red linebelow, we can see that R2 can reach 10.0.4.0/24 also with 3 hops via interfaceeth0 wich leads to R1.

R>* 10.0.0.0/24 [120/2] via 10.0.1.1, eth0, 00:01:10C>* 10.0.1.0/24 is directly connected, eth0R>* 10.0.2.0/24 [120/2] via 10.0.1.1, eth0, 00:01:10R>* 10.0.3.0/24 [120/5] via 10.0.1.1, eth0, 00:00:43R>* 10.0.4.0/24 [120/3] via 10.0.1.1, eth0, 00:00:43R>* 10.0.5.0/24 [120/4] via 10.0.1.1, eth0, 00:00:43R>* 10.0.6.0/24 [120/5] via 10.0.1.1, eth0, 00:00:43C>* 127.0.0.0/8 is directly connected, lo

Item 2 Proof

If we take in consideration R2 again, it has two possible ways to reach network10.0.2.0/24 with different Hop cost: R2 -> R1 or R2 -> R3 -> R5 -> R4.In the red line below, we can see that R2 can reach 10.0.2.0/24 with 2 hops viaeth0 wich leads to R1.

R>* 10.0.0.0/24 [120/2] via 10.0.1.1, eth0, 00:07:42C>* 10.0.1.0/24 is directly connected, eth0R>* 10.0.2.0/24 [120/2] via 10.0.1.1, eth0, 00:07:42C>* 10.0.3.0/24 is directly connected, eth1R>* 10.0.4.0/24 [120/3] via 10.0.3.2, eth1, 00:07:41R>* 10.0.5.0/24 [120/2] via 10.0.3.2, eth1, 00:07:41R>* 10.0.6.0/24 [120/2] via 10.0.3.2, eth1, 00:07:41C>* 127.0.0.0/8 is directly connected, lo

INSERT IP ROUTE WITH R2 ETH0 SHUTDOWN

Question 2

Analyse and comment on the IP address configuration of the routers/hosts interfacesthat was assigned by CORE.

5

Core emulater auto-assigned 10.X.Y.0/24 ip adresses. This is the private ip pooland RFC 1918 standard. Class C addresses use the last octet to identify each hostwhich means each network can have up to 254 hosts. Class C addresses and are commonlyused for small to mid-size businesses. Considering the size of this project, usingclass C seems like a good fit.

Question 3

Configure all routers of the topology to use the RIP protocol for routing dissemina-tion of all interconnection and end-user networks.

Core makes protocol interchange easy, to accomplish this, all we have to do is toselect each different device, right-click -> Services and make sure RIP protocol isenabled as showed in the following figure:

Figure 2: Enabling RIP protocol

6

Question 4

Activate the defined topology and undertake connectivity tests (e.g ping etc.) be-tween the various routers/networks and check the used routes.

To test the network connectivity we chose some devices that combined use the wholenetwork. If this nodes are connected, it means that the middle networks also haveconnectivity between each other. We used the ping command to test the connectivity onthe following devices:

• PC-B1 -> PC-C1asdasd

• PC-B1 -> PC-C2

• PC-B2 -> PC-C1

• PC-B2 -> PC-C2

Considering that the hosts communicate within the shortest path in terms ofhop metric, we tested separately the connectivity between the unused paths.

• R1 -> R5

• R5 -> B3

Question 5

1. View and analyze the routing tables that were established by the routers of thecore network. [note: a specific routing table considered relevant for thispurpose should be selected and explained in detail]

We considered R3 as a good test subject for this question. By using the commandshow ip route in the routers terminal, we obtain it’s routing table:

R>* 10.0.0.0/24 [120/3] via 10.0.3.1, eth0, 00:05:32R>* 10.0.1.0/24 [120/2] via 10.0.3.1, eth0, 00:05:34R>* 10.0.2.0/24 [120/3] via 10.0.3.1, eth0, 00:05:32C>* 10.0.3.0/24 is directly connected, eth0R>* 10.0.4.0/24 [120/2] via 10.0.5.1, eth1, 00:05:34C>* 10.0.5.0/24 is directly connected, eth1C>* 10.0.6.0/24 is directly connected, eth2C>* 127.0.0.0/8 is directly connected, lo

7

RouteSource

DestinationNetwork

AdministrativeDistance and Hop

metric

Next-hop OutgoingInterface

RouteTimes-tamp

R>* 10.0.X.Y [120/H] 10.0.A.B ethZ HH:MM:SS

Route source: Identifies how the route was learned, in this case R stands forRIP.Destination Network: Identifies the address of the remote network.Administrative Distance: 120 by default, identifies the trustworthiness of theroute source.Hop Metric (H): Identifies the value assigned to reach the remote network. lowervalues indicate preferred routes.Outgoing Interface: Identifies the exit interface to use to forward a packettoward the final destination.Route Timestamp: Identifies from when the route was last heard.

Route Source Destination Network Outgoing InterfaceC>* 10.0.X.Y/24 ethZ

If the Route Source is a C it means the Source is directly connected to the des-tination network through the Outgoing Interface.

2. View and analyze the routing tables of the hosts of the user-networks. [note:explain in detail a specific routing table of one of the hosts]

On the hosts side the routing table differ a little bit. To exemplify its contentswe run the command route -n on the Host PC-C2 and got the following result:

Destination Gateway Genmask Flags Metric Ref Use Iface0.0.0.0 10.0.6.1 0.0.0.0 UG 0 0 0 eth010.0.6.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0

Destination: Identifies the address off a remote network.Gateway: Identifies the gateway Address.Genmask: The netmask for the destination net; 255.255.255.255 for a host desti-nation and 0.0.0.0 for the default route.Flags: U stands for (route is up) and G for (use gateway).Metric: The distance to the target . In this case 0 because the host is directly

8

connected to the router.Ref: Number of references to this route. (Not used in the Linux kernel.)Use: Count of lookups for the route.Iface: Interface to which packets for this route will be sent. In this case thehost only has one interface(eth0).

This host has learned two routes: 0.0.0.0 is the default route, a default routeis used when no other routes for the destination are found in the routing table;and 10.0.6.0 which is the local network.

Question 6

Assume that the administrator wants to change the time interval by which are generatedthe RIP updates messages. What command could be used for this purpose?

To change the time interval we use the command timer basic A B C inside a Routerterminal in config mode, where A, B and C are as follows:

• A: The value in seconds to which the routing table must update (30 as default).

• B: The value in seconds to which the information times out (180 as default).

• C: The value in seconds for the garbage collection (120 as default).

Has an example of the chain of commands necessary we used R1 as test subject:

R1# configure terminalR1(config)# router ripR1(config-router)# timer basic 30<5-2147483647> Routing table update timer value in second. Default is 30.

R1(config-router)# timer basic 60<5-2147483647> Routing information timeout timer. Default is 180.

R1(config-router)# timer basic 60 360<5-2147483647> Garbage collection timer. Default is 120.

R1(config-router)# timer basic 60 360 240

Question 7

Through the configuration console of the routers shutdown one (or more) interconnec-tion links/interfaces in order to originate two distinct scenarios:

1. Even with the disabled interface(s) all routers/networks of the topology canmaintain connectivity

2. Some of the routers/networks have no available paths to reach other routers/net-works of the topology.

Item 1 ProofMISSING

9

Item 2 ProofTo cut the connection from one router with the rest of the topology we chose the routerR2. Initially, we did a path test between R1 and PC-C2 and obtained Figure 3.

Figure 3: Connection path between R1 and PC-C2

We can see that R1 chooses R2 as a path to reach PC-C2. Now, to alienate R2 we cutboth of R2’s interfaces. We do this by going to the R2 terminal, entering configurationmode, selecting the interface we desire to change and apply the shutdown command. Werepeat this step for both of R2’s interfaces. To undo this command we can run noshutdown.After shutting down the interfaces we run show interface and verify that both are downas we can see in Figure 4.

Now if we run show ip route we see that the next hop to reach the network 10.0.6.0/24is through R4:

R1# sh ip routeCodes: K - kernel route, C - connected, S - static, R - RIP,

O - OSPF, o - OSPF6, I - IS-IS, B - BGP, A - Babel,> - selected route, * - FIB routeC>* 10.0.0.0/24 is directly connected, eth0C>* 10.0.1.0/24 is directly connected, eth1C>* 10.0.2.0/24 is directly connected, eth2R>* 10.0.4.0/24 [120/2] via 10.0.2.2, eth2, 00:02:07R>* 10.0.5.0/24 [120/3] via 10.0.2.2, eth2, 00:00:06R>* 10.0.6.0/24 [120/4] via 10.0.2.2, eth2, 00:00:06C>* 127.0.0.0/8 is directly connected, lo

Question 8

Configure one of the routers of the topology so that the traffic that it transmitsto a particular destination network not cross the path with the smaller number of

10

Figure 4: Confirmation that both of R2’s interfaces are shutdown.

hops, but another alternative path (i.e. in the example in Figure 1, to send trafficto “rede B” the “router y” will use the path that passes through the “router x. Forall other destinations the path with the least number of hops will continue to be thechosen one). [hint: in the theoretical lectures a specific command that solves thisissue was mentioned]

MISSING

Question 9

Assume that your network will be connected to another external network via router x(see Figure 2). Present and explain the configuration command(s) that will be usedto assure that all traffic directed to external networks leave the domain using therouter x.

First we added an external network to the topology and after we used the commandip route 0.0.0.0 0.0.0.0 10.0.7.2 in the R4. This command sets the gateway of lastresort to 10.0.7.2 which means all traffic that is not local will be sent to thisrouter. Onde the topology is set to redirect to the external networks via 10.0.7.2 weran default-information originate, with this we advertise the default route to therest of the topology. In the end we did various connectivity tests from differentrouters to the external network.

11

Figure 5: Traceroute from R5 to the external host


12


Figure 8: Ping from PC-B1 to the external host

13

Figure 9: Ping from PC-C1 to the external host

14

Engineering

Rip and OSPF assignment (RIP ба OSPF дасгал ажил)