Understanding Computer Networking: Routing Tables, Switching, and IP Addressing, Lab Reports of Computer Systems Networking and Telecommunications

Download Understanding Computer Networking: Routing Tables, Switching, and IP Addressing and more Lab Reports Computer Systems Networking and Telecommunications in PDF only on Docsity! LET'S ALL WELCOME THESE TWO LOVELY GENTLEMEN FROM THE FBI WHO ARE VISITING WITH US TODAY SO THAT THEY CAN ARREST GOMEONE KNOWN ONLINE AS "MAPUABOY" ... rte ork { ") rc 4 ra 5  208.16.2.1 201.3.4.4 Typical Student 110; E492 | lov 208.16.3.0 <<} ROUTER Lab Topology subnet #3 192.168.x.0 192.168.1.1 201.3.4.3 subnet 3640 oe 1/0 Boe 0/0 Linux SWITCH ; ROUTER ROUTER B 192.168.1.0 #2 subnet Station X 192.168.0.0 2916 SWITCH 10/23/2008 192.168.0.1 1/0 Core Edge subnet Windows SWITCH A ROUTER #1 192.168.0.0 subnet Computer Networking 201.3.4.2 0/0 10/23/2008 6 Computer Networking The LABS Every lab starts with these 4 steps: 1. Power up your equipment and log into your PCs. 2. Wire your network. 3. Configure PC1 and PC2, assigning to each an: (1)IP address (2)Netmask (3)DNS server IP address (usually optional) (4)Default gateway IP address -- Set each PC’s default gateway to its nearest router interface IP address. 4. Configure your router. Computer Networking 10/23/2008 7 Computer Networking The LABS 1. You will ALWAYS boot the Linux Knoppix CD on one of your PCs. To become root, enter: su 2. You will ALWAYS log in as Administrator on the Windows PC. The password is: baun212 3. You will ALWAYS assign to PC1 (Linux) the address a.b.c.10x where a.b.c.0 is the subnet address, 10x is the PC address, and x is your Station number. 4. You will ALWAYS assign to PC2 (Windows) the address d.e.f.20x where d.e.f.0 is the subnet address, 20x is the PC address, and x is your Station number. 5. You will ALWAYS assign IP addresses to your router’s interfaces in the following way: If the interface is on a subnet that only you use, it will be a 192.168.x.0 subnet. Assign the address 192.168.x.1, where x is your Station number. If the interface is on a subnet that you share with others, assign the address a.b.c.xx, where x is your Station number. Computer Networking Ethernet uses Manchester Data Encoding • No need for a centralized, global clock among the nodes! • Allows clocks in sending and receiving nodes to synchronize to each other • Every (Manchester) data transition equals a falling of the global clock – a data rising edge = 1; a data falling = 0 Computer Networking 10/23/2008 10Computer Networking 10/23/2008 11Computer Networking Ethernet -- CSMA/CD •Ethernet originally used a shared coaxial cable winding around a building or campus to every attached machine. •A scheme known as carrier sense multiple access with collision detection (CSMA/CD) governed the way the computers shared the channel. •When a computer want to send a frame to another computer, perform this Main Procedure: 1. Frame ready for transmission. 2. Is medium idle? If not, wait until it becomes ready and wait the inter-frame gap period (9.6 µs in 10 Mbit/s Ethernet). 3. Start transmitting. 4. Did a collision occur? If so, go to collision detected procedure. 5. Reset retransmission counters and end frame transmission. Computer Networking 10/23/2008 12Computer Networking Ethernet -- CSMA/CD (cont.) •Collision detected procedure 1. Continue transmission until minimum packet time is reached (jam signal) to ensure that all receivers detect the collision. 2. Increment retransmission counter. 3. Was the maximum number of transmission attempts reached? If so, abort transmission. 4. Wait random back-off period based on number of collision 5. Re-enter Main Procedure (previous slide) at stage 1. •This can be likened to what happens at a dinner party, where all the guests talk to each other through a common medium (the air). Before speaking, each guest politely waits for the current speaker to finish. If two guests start speaking at the same time, both stop and wait for short, random periods of time (in Ethernet, this time is generally measured in microseconds) and try again. Computer Networking 10/23/2008 15Computer Networking Computer Networking The Equipment Hub – a Layer 1 device • Yes, there are “smart” hubs (with microprocessors) that do switching, but ours are “dumb.” Switch – a Layer 2 device • Yes, there are some “Layer 3 switches” that do routing, but ours merely switch. Router – a Layer 3 device • To keep things simple, our hubs are pure Layer 1, our switches are pure Layer 2, and our routers are pure Layer 3 (except for the Ethernet interfaces = Layer 2). 10/23/2008 16 Computer Networking Routers learn IP address-interface pairings so… 1. Either you “teach” them by telling them on which interface each subnet can be reached 2. Or they learn from data collected by a dynamic routing protocol, such as RIP or OSPF Either way, the pairings are entered into a routing table Computer Networking 10/23/2008 17 Computer Networking Switches learn MAC address-port pairings autonomously 1. Switch receives frame from host C and makes a table entry noting that C is on interface 1 2. Because D is not in the table, switch forwards frame into all interfaces – that is, 2 and 3 3. Host D receives the frame 4. Switch receives response frame from D and makes a table entry noting that D is on interface 2 5. Because C is already in the table, switch forwards frame only to interface 1 Computer Networking Hubs cannot learn – no uP, no memory Switches isolate traffic – security! MAC address INTERNET Switch pc |[ Pc S/T 60 S/T pc || PC | PC} pc PC 10/23/2008 Computer Networking 20 10/23/2008 21 Computer Networking Configure PC1 for use in the 192.168.1.0 subnet. Open a terminal window and enter: # su
switch user to root (the default user to switch to) # ifconfig eth0 192.168.0.10x
x = your Station number # ifconfig eth0 netmask 255.255.255.0
eth0 = NIC # route add default gw 192.168.1.1
gw = gateway Computer Networking Your SWITCH Your ROUTER CON PC1 Linux PC2 Windows COM1 X-Over Serial Cable 192.168.1.0 subnet 192.168.0.0 subnet 192.168.0.0 subnet 10/23/2008 22 Computer Networking Configure PC2 for use in the 192.168.0.0 subnet. 1. Right click “My Network Places.” Left click “Properties.” Right click “Local Area Connection.” Left click “Properties.” Left click “Internet Protocol (TCP/IP).” Left click the “Properties” button. Left click “Use the following IP address.” 2. Set the IP address to 192.168.0.20x (where x is your Station number). Set the Subnet Mask to 255.255.255.0.
Logically AND IP address with mask to get the subnet. 3. Set the default gw to 192.168.0.1. This will be your router’s right interface IP address, which you will set in the next step. 4. In a DOS window, check config using ipconfig command. Computer Networking Your SWITCH Your ROUTER CON PC1 Linux PC2 Windows COM1 X-Over Serial Cable 192.168.1.0 subnet 192.168.0.0 subnet 192.168.0.0 subnet Computer Networking NVRAM • Exclusively used to store the starting configuration file (which is parsed on power-up) # sh start
show starting configuration • Contents are retained on power-down 10/23/2008 25Computer Networking Computer Networking FLASH • EEPROM (Electronically Erasable Programmable ROM) • Contents retained on power-down • May be off-board in the form of flashcards • Stores the IOS, so NEVER erase it! • Multiple versions of IOS may be stored at once 10/23/2008 26Computer Networking Computer Networking ROM • Generally installed in factory and never touched again • POST (power-on self test) • Bootstrap program that calls IOS • Bare-bones version of an IOS. If IOS load routine fails, it defaults back to this version, giving limited functionality 10/23/2008 27Computer Networking Computer Networking IOS (Internetworking Operating System) • Simply typing “?” will give you a complete list of the commands available to you in the mode you are in > en
Enter privileged EXEC (enabled) mode # ? • Typing the “?” character after a command gives you a list of options: # show ? # show ip ? • Typing the “?” character at some point during a word gives you a list of commands that start with what you have so far For instance, typing: # ac? Will ask the IOS what commands begin with “ac” 10/23/2008 30Computer Networking 10/23/2008 31 Computer Networking Configure your router. 1. Connect the COM1 port on PC2 (the Windows box) to your router’s CON port. Use an adaptor. 2. Run HyperTerminal: (See the Configuring your Router via HyperTerminal handout.) 3. Answer all of your router’s “yes/no” questions with a NO. The router comes up in User EXEC mode (with a ‘>’ prompt). You can’t do much in this mode. 4. Ensure there is no stored configuration by entering: > enable
Enter the privileged EXEC mode # sh start You should get a message saying there is no startup configuration. If you get a listing of a configuration, erase it so: # erase start
yes, you really want to do this Turn your router off/on to remove the running configuration. Computer Networking 10/23/2008 32 Computer Networking Configure your router. The serial cable is used to configure the router using PC2. Give your router a hostname, using “Routerx,” where x = your Station number. # config t
Enter the global config mode # hostname Routerx
Where x = Station number # <Ctrl-c>
Exits the Global config mode Computer Networking 10/23/2008 35 Computer Networking Okay, let’s see you if understand the rules…. (All networks are class C) Computer Networking 10/23/2008 36 Computer Networking Configuration Practice • The IP address of PC1 should be: _______________________ • The IP address of PC2 should be: _______________________ • The default gateway (route) for PC1 should be: ____________ This is the IP address of your router’s left interface! • The default gateway (route) for PC2 should be: ____________ This is the IP address of your router’s right interface! Computer Networking NOTE: You are the only user of your two router interfaces. 10/23/2008 37 Computer Networking Configuration Practice (assume Station 2) • PC1 is on subnet: ____________________________________ • PC2 is on subnet: ____________________________________ • The IP address of PC1 should be: _______________________ • The IP address of PC2 should be: _______________________ • The default gateway (route) for PC1 should be: ____________ • The default gateway (route) for PC2 should be: ____________ This is the IP address of your router’s right interface! Computer Networking NOTE: You are the only user of your two router interfaces. 10/23/2008 40 Computer Networking Configuration Practice (assume Station 6) • The IP address of PC1 should be: _______________________ • The IP address of PC2 should be: _______________________ • PC2 is on subnet: ____________________________________ • The default gateway (route) for PC1 should be: ____________ • The default gateway (route) for PC2 should be: ____________ Computer Networking NOTE: You share your router’s left interface via Core Switch A. 10/23/2008 41 Computer Networking Configuration Practice (assume Station 7) • The IP address of PC1 should be: _______________________ • The IP address of PC2 should be: _______________________ • The default gateway (route) for PC1 should be: _____________ • The default gateway (route) for PC2 should be: _____________ • The IP address of your router’s right interface should be: _____ Computer Networking 10/23/2008 42 Computer Networking Configuration Practice (assume Station 8) • The IP address of PC1 should be: _______________________ • The IP address of PC2 should be: _______________________ • The default gateway (route) for PC1 should be: _____________ • The IP address of your router’s left interface should be: ______ • The IP address of your router’s right interface should be: _____ Computer Networking Router Architecture Overview Two key router functions: J run routing algorithms/protocol (RIP, OSPF, BGP) oO ferwarding datagrams from incoming to outgoing link input port output port 4 [HOI . switching « . . s . input port fabric output port routing processor 10/23/2008 Computer Networking 45 10/23/2008 46 Computer Networking Static Routing Configuring Static Routes in Cisco Routers: ip route <network><mask><next hop|exit i/f> – network - the destination subnet (e.g. 236.16.3.0) – mask - the subnet mask for that network (e.g. 255.255.255.0) – next hop (IP address of the next hop router’s interface) or the exit interface – Examples: ip route 192.168.0.0 255.255.255.0 fa0/0 ip route 192.168.0.0 255.255.255.0 201.3.4.2 “Any subnet a router will not talk to does not require a route to.” Computer Networking 10/23/2008 47 Computer Networking The configuration of Edge Router #1 (must use next hop): ip route 192.168.1.0 255.255.255.0 201.3.4.3 ip route 192.168.2.0 255.255.255.0 201.3.4.3 ip route 192.168.3.0 255.255.255.0 201.3.4.3 ip route 192.168.4.0 255.255.255.0 201.3.4.3 ip route 192.168.5.0 255.255.255.0 201.3.4.3 ip route 192.168.6.0 255.255.255.0 201.3.4.3 ip route 192.168.7.0 255.255.255.0 201.3.4.3 ip route 192.168.8.0 255.255.255.0 201.3.4.3 ip route 208.16.3.0 255.255.255.0 201.3.4.4 Computer Networking 10/23/2008 50 Computer Networking What happens when PC1 pings PC2? 1. You can ping your router’s left interface; your router knows you 2. You can ping your router’s right interface; your router knows you 3. You can ping your Edge Router #2’s left interface • The router has a route to you 4. You cannot ping Edge Router #2’s right interface • Your router drops the packet – doesn’t know 201.3.4.0 Computer Networking 10/23/2008 51 Computer Networking For PC1 to ping Edge Router #2’s right interface, your router needs to know about the 201.3.4.0 subnet (the destination). So you ENTER: ip route 201.3.4.0 255.255.255.0 192.168.1.1
next hop If there were no other (student station) routers connected to Core Switch B, you could use: ip route 201.3.4.0 255.255.255.0 fa0/0
exit interface Computer Networking 10/23/2008 52 Computer Networking For PC1 to ping PC2, your router needs to know about the 192.168.0.0 subnet (the destination). So you ENTER: ip route 192.168.0.0 255.255.255.0 192.168.1.1
next hop If there were no other (student station) routers connected to Core Switch B, you could use: ip route 192.168.0.0 255.255.255.0 fa0/0
exit interface Computer Networking Computer Networking Dynamic Routing If one could count on a network operating in a static configuration with no failures and no changes ever being made, the routing problem would be simple: static tables could suffice as the basis for all routing decisions. For each packet destined to a particular destination, the next hop would be identified in the table, and the packet would be forwarded. However, in the real world, nodes are added to or deleted from networks, links fail, and topologies change. As networks get larger, administration and management headaches increase. Therefore, automated route management (dynamic routing) rapidly becomes a necessity. 10/23/2008 55Computer Networking Computer Networking The Internet architecture is based on the concept of the interconnection of many "Autonomous Systems." An Autonomous System (AS) (e.g. UOP, or an ISP) is characterized by a single management authority along with the use of a consistent routing architecture. Each AS is responsible for the maintenance of its own routing. The routing algorithms used within the AS are referred to as Interior Gateway Protocols. The routing algorithm used to connect the AS to the Internet is referred to as Exterior Gateway protocols. Several exterior gateway protocols are in use today, but the most popular is BGP4 (Border Gateway Protocol v4). 10/23/2008 56Computer Networking Computer Networking Interior Gateway Protocols use two types of dynamic routing algorithms. These are: – Vector-distance (or Distance-vector) • RIP (Routing Information Protocol) is the best example – it is built into IOS – Link-state • OSPF (Open Shortest Path First) is the best example – OSPF is perhaps the most widely-used interior gateway protocol in large enterprise networks – IS-IS (Intermediate System to Intermediate system), another link-state routing protocol, is more common in large service provider networks • IGRP (Interior Gateway Routing Protocol) is the link- state algorithm - it is built into Cisco’s IOS 10/23/2008 57Computer Networking 10/23/2008 60 Computer Networking Link-state: IGRP (Interior Gateway Routing Protocol) IGRP Configuration Practice: Edge Router #1: # config t
AS = Autonomous System # router igrp 1
Must give yourself an AS number # network 192.168.0.0
IGRP assumes classful routing # network 201.3.4.0 Computer Networking 10/23/2008 61 Computer Networking Link-state: IGRP (Interior Gateway Routing Protocol) IGRP Configuration Practice: Edge Router #2: # config t
AS = Autonomous System # router igrp 1
Must give yourself an AS number # net 201.3.4.0
IGRP assumes classful routing (class C) # net ___________
can use net for short Computer Networking 10/23/2008 62 Computer Networking Link-state: IGRP (Interior Gateway Routing Protocol) IGRP Configuration Practice Edge Router #3: # config t # router igrp 1 # net ___________
ER #3’s right interface (0/0) # net ___________
ER #3’s left interface (0/1 or 1/0) Computer Networking 10/23/2008 65 Computer Networking Vector-distance: RIP (Router Information Protocol) RIP Configuration Practice Edge Router #2: # router rip # net ________________ # net 201.3.4.0 Computer Networking 10/23/2008 66 Computer Networking Vector-distance: RIP (Router Information Protocol) RIP Configuration Practice Edge Router #3: # router rip # net ________________ # net 201.3.4.0 Computer Networking 10/23/2008 67 Computer Networking Vector-distance: RIP (Router Information Protocol) RIP Configuration Practice Your Router (assume Station 2): # router rip # network _______________
right interface # network _______________
left interface Computer Networking