Vorlesung Routingprotokolle. Lab time 1: Routing with RIPnG and IPv6. Target. Tasks

Transcription

1 Vorlesung Routingprotokolle Lab time 1: Routing with RIPnG and IPv6 Target Stand: 28. August 2014 Planning of IPv6 networks Assign correct IPv6 addresses to the correct router interface Configure a network with a preconfigured physical layout Gathering Know-How of basic (cisco-) router config commands Testing and troubleshooting skills Tasks Please read part A of this document and create a proper IPv6 address layout prior to the lab time It is strongly advised to read part B as well in order to know what is expected during the lab. This is especially recommended so that you will be able to finish the lab in time. Please note that it is your responsibility to know all required CISCO command line commands for this lab. IPv6_RIPRouting-Englisch.odt. Page 1 of 14

2 Part A: Preparation before the lab Scenario You are the network administrator of a small company. The picture shown below describes your network. Your ISP now assigns you a set of IPv6 addresses. It is your task to implement IPv6 inside your network with the address prefixes given to you. Also, all networks (and routers) should be reachable from everywhere in your network. That means that you should use RIPnG to distribute all addresses inside your network. We simulate the ISP to be in the LAN network of router C, that means you should create a default IPv6 route pointing to a fictious IPv6-address inside this network. A.1 Planning of IPv6 addresses Network topology Given prefix: 2001:41b8:9bf:fc10::/61 FA 0/0 S0/1/0 S0/1/1 FA 0/0 S0/1/1 S0/1/0 FA 0/0 FA 0/1 FA 0/1 FA 0/0 Be anware that the routers in the lab may have different names for their interfaces. I.e.instead of FastEthernet 0/0 it might be GigabitEthernet 0/0 or instead of Serial0/0 it might be Serial0/0/0. It is advised to examine every router for the correct interface names. This can be done with the command show ip interface brief. Page 2 of 14

3 Analysis of network requirements and distributing the address space. You must adhere to the following address rules: All LAN-interfaces of the routers must have manually assigned addresses. This should be the first possible address in the subnet All router-router interconnects should have appropriate addresses with a subnet size as small as possible All PCs will receive their addresses by stateless auto configuration Question: what subnet mask does the smallest possible IPv6 subnet have if it should be used for auto configuration? Your service provider assigned the address space 2001:41b8:9bf:fc10::/61 to your network. The following networks should receive a IPv6 subnet address (remember: PC's will have auto configuration) o LAN A, B, C and D o connection between Router C and B o connection between Router B and A o connection between Router A and D ID Network Prefix Router host address(es) LAN A LAN B LAN C LAN D Router A-D Router B-A Router C-B The router LAN interfaces should also receive the first possible link local address Planning for future network extensions The remaining address space should be assigned for the (not yet) existing network segments that might be set up in the future Complete the following address table for future extensions (it might be possible that there are fewer prefixes available than the table has lines) Page 3 of 14

4 ID Network Prefix Router host address reserved reserved reserved reserved Creation of interface addresses As mentioned previously, the LAN interface addresses should be according to this rule: Every router will receive the lowest possible address of the respective subnet, I.e. 2001:41b8:9bf:fc10::x (x being the lowest number) Question: How do the end systems (PCs) receive their address? Page 4 of 14

5 Part B Lab work B.1 create the physical connection according to the plan The majority of the cabling work might already be done. However it is strongly advised to check the cabling Attention: Every serial interface whose name ends with a 0 (i.e. Serial 0/0 or Serial1/0/0) must have the clock rate configured. This is a simulation of a real world physical connection. The correct command will be clockrate Physical connections to the router All cisco routers (and some switches) do have a so called console interface. This is a serial interface with direct access to the command line. You will use your PC as a terminal to connect to the routers and to create the configuration. This cabling is already done, you should NOT change that. Every PC has one connection to one of the routers. Picture 1: Example of a serial connection to the router In addition to that Every PC does have two red cables on the back. One of the cables is attached to the serial interfaces. DO NOT TOUCH THIS CABLE FOR OTHER PURPOSES THAN CHECKING FOR GOOD CONNECTION! The second red cable is an ethernet connection to your lab network. If the grey cable is attached the computer has connection to the university network. You must use the red cable to test your network. Serial connection We will use a program called PUTTY to connect to the console interface of the router Page 5 of 14

6 start PUTTY configure PUTTY as shown Click OK : If you configured correctly you should see some output from the router. If not, just press enter a few times and check the serial connection. You are now in user mode. This is indicated by the prompt ">". Change to priviledged mode. The command to use is enable If the router now asks for a password, try cisco or Cisco. If that fails ask the lab personal. If the command was successful, the prompt will change to #. Create the basic configuration. It is important that you delete all old configurations by typing Router#copy flash:start0-cfg startup-config Router#reload After the boot process (which may take a while) you should see the prompt "Router>". Now create the basic configuration, i.e. router hostname, passwords You also should implement your IPv6 address configuration now Tip: you may use a pre fabricated command set as a text file. You then can use cut&paste in PUTTY to deliver the commands to the router. The first line should be the command configure terminal. An example configuration is in Schedule 1. Be sure to be in the priviledged mode (with the command enable ). You should see the prompt Router#. Save the configuration with the command (copy run start). If you do not do this every power outage will remove all of your configuration work. Page 6 of 14

7 You can control your configurations with the following commands to check the interface status use: show ip interface brief respective show ipv6 interface brief Every active interface should have the status [up/up]. ISP#show ipv6 interface brief FastEthernet0/0 [up/up] FE80::21B:D4FF:FE3D:D :41B8:9BF:FC04::1 FastEthernet0/1 [up/up] FE80::21B:D4FF:FE3D:D :41B8:9BF:FC00::115 Serial0/1/0 [administratively down/down] unassigned Serial0/1/1 [up/up] FE80::21B:D4FF:FE3D:D :41B8:9BF:FC05::11 ISP# If not either your neighboring routers are not yet configured or do have the wrong configuration. Or there is a failure in the cabling. Try to find the fault before asking for help. Check the forwaring table (Routing Table) Use show ip route and document the result: Use show ipv6 route and document the result: As you should see right now, only the directly attached networks are present! Check the connection to the neighboring routers There will be no connectivity between the PCs yet. However, if configured correctly, shou should be able to connect to the neighboring router and to connect from the PC to the LAN router interface. It is mandatory that you are able to ping from router to router and from the PC to the local LAN gateway (router's LAN interface) If you try to ping some other PC you should fail. Question: Why does the ping from PC A to PC B (or others) fail? What is missing? If you are not sure, check the forwarding table... Page 7 of 14

8 B.2 Configuration of static routes Static routing Routers are used to interconnect networks. To be able to forward data packets they calculate the path to the know destination networks and forward the data packets along that path Static routing means that the path is not calculated but created by hand. The administrator configures every router with preset pathes. This is done by configuring static routes. Every destination network will be configured with a so called nex hop address pointing to the next router in the path to that destination. You do not need to configure the directly connected networks because S0/0 (DCE) they are already known by the router- In order to forward packets to a destination the router will make a lookup in the forwarding table to find the corresponding next hop for a destination address. It will look for the longest prefix match first. If a proper next hop address is found the packet will be sent to that address. If there is no corresponding entry in the forwarding table, the router will return a "ICMP destination unreachable" message back to the original sender and will discard the packet. To prevent this usually the administrator will create a default route. I will now explain what lines you should expect in the forwarding table for the network example as shown (BRANCH1 and BRANCH2) A local LAN with just one exit router is called a stub network. That means, the LAN of router BRANCH2 (BRANCH2-LAN) is such a stub network. In such a network there is nothing to decide. The PC can only forward the packets to the router BR2. Also, the router BR2 can forward the packets to the BR1 only. There is no other router in the network... In such cases, a simple default route is sufficient. For IPv6 the command is ipv6 route ::0/0 <next-hop address > The next hop address is (in this example) the IPv6 address of the S0/1 interface of router BR1. Please note that the lab does have different networks and interfaces. You should add exactly ONE static default route and this should point to an address in the range of the LAN of router C. Please consider that this address will be <PREFIX>::FF, with <PREFIX> as the prefix you've chosen for LAN C. Default route for the other routers As mentioned, the ISP should be connected inside the LAN of router C. In the previous task you configured the default route for router C. However, you now must configure all other routers with an appropriate default route. Create the default routes for all other routers BRANCH1-LAN BR1 S0/1 HQ-BR1 link BRANCH2-LAN Display the routing table and highlight the default static route in the box: S0/0 (DCE) S2 BR2 PC2 Page 8 of 14

9 Now do the following test: PC B does ping PC C. Successful? traceroute (tracert) from PC B to PC D. What kind of problem does exist? ([CTRL+C] does stop the tracert) Explain why both tests fail. What do you need to do to make these tests successful? Page 9 of 14

10 Configuration of RIPnG It is possible to create static routes in a network. However this wil be hard to maintain in larger environments. Therefore one should use a dynamic routing protocol. The following task will let you configure RIPnG as routing protocol in your network so that every node can connect with every other node. Important: All interfaces and all networks must be distributed by RIP. This includes the default route to the ISP. What commands are required for this task? Before configuring, display and record the IPV6 routing table After the configuration redisplay the routing table and record it here What did change and why? Test of the config Perform the following tests: PC B ping PC C (ping -6). Successful? traceroute (tracert -6) from PC B to PC D. Is there a problem? ([CTRL+C] does stop tracert) Page 10 of 14

11 Please make these tests with all other PCs in your network. If one or every test fails please troubleshoot your config. This should not happen. Now, create a permanent ping between PC B and PC D (ping -6 -t) When the ping is working, shutdown the interface on router A that is connected to router D. Check on 1. how long does it take after shutdown of the interface before the ping fails? 2. How long does it take before router C removes the entry of the LAN D from it's forwarding table? Check by continuously display the forwarding table (show ipv6 route) Now reconnect the interface (no shutdown) and 1. how long does it take until the ping starts working again? 2. How long does it take until router C has the entry for LAN D in it's forwarding table? Page 11 of 14

12 Schedule 1: Sample config Sample configuration: configure terminal hostname Router D enable secret class no ip domain lookup no ip name server ipv6 unicast routing interface FastEthernet0/0 ipv6 address 2003:AFFE:CAFFE:FC00::1/64 no shutdown interface FastEthernet0/1 ipv6 address 2003:AFFE:CAFFE:FC01::1/64 no shutdown interface Serial0/1/0 ipv6 address 2003:AFFE:CAFFE:FC02::1/64 clock rate no shutdown interface Serial0/1/1 no ip address shutdown line con 0 password cisco login! Sitzungsdauer 240 Minuten exec timeout 240 line vty 0 4 password cisco login! Sitzungsdauer 240 Minuten exec timeout 240 end copy running config startup config Page 12 of 14

13 Schedule 2: Useful router commands IOS commands Router#configure terminal Router(config)#enable secret class Router(config)#ipv6 unicast routing Router(config)#line console 0 Router(config line)#password login passwort Router(config line)#login Router(config)#line vty 0 4 Router(config line)#password login passwort Router(config line)#login Router(config)#interface interface name Router(config if)#ip address ipaddress subnetmask Router(config if)#ipv6 address ipv6address/prefixlength Router(config if)#shutdown Router(config if)#no shutdown Router(config if)#description text Router(config if)#clockrate frequency (e.g ) Router(config if)#ipv6 rip Processname enable Router(config)#ipv6 route DestNetwork_IP_Addr subnetmask nexthopinterfaceip Router(config)#ipv6 route ipv6 Destination net address interface name ipv6 nexthop address Router(config)#ipv6 router rip Processname Router(config)#no ipv6 router rip Processname Router#show running config Router#show startup config Router#show ipv6 interface Router#show ipv6 interface brief Router#show ip route Router#show ipv6 route Router#show ipv6 protocols Page 13 of 14

14 Router#clear ip route * Router#erase startup config Router#reload Router#copy running config startup config Page 14 of 14