1. CISCO NETWORKING ACADEMY Chabot College ELEC 99.05 Addressing & Routing Foundation Concepts

2. CISCO NETWORKING ACADEMY Switches & Bridges (review) Layer-2 device Reduce large collision domains Uses MAC address table to determine whether or not to forward a frame

3. CISCO NETWORKING ACADEMY Switches & Bridges (review) Make “low level” decisions Flood the network if address unknown Always forwards broadcasts –Excess broadcast traffic can result

4. CISCO NETWORKING ACADEMY Layer 2 Switch Limitations Switches & Bridges: Don’t handle device moves well Can’t control broadcast traffic Lack path determination abilities Have limited address capacity

5. CISCO NETWORKING ACADEMY Layer 2 Switch Limitations Switch doesn’t handle device moves well. –When a device is moved from one switch port to another, the switch’s MAC address table will be wrong until it is “flushed” or “ages out”.

6. CISCO NETWORKING ACADEMY Layer 2 Switch Limitations Switch can’t control broadcast traffic. –Switches (and bridges) always forward broadcast traffic, which is essential to LAN operation. –Broadcasts only stop at the edge of the network. –Excess broadcast traffic can result.

7. CISCO NETWORKING ACADEMY Layer 2 Switch Limitations Path determination abilities –Almost no ability to determine paths when there are multiple routes from source to destination. –No ability to change paths when a route becomes unavailable.

8. CISCO NETWORKING ACADEMY Layer 2 Switch Limitations Limited address capacity –There are 10’s of millions of MAC addresses in the world, but the typical switch can store only a few thousand MACs. –Fine for LANs, but inadequate for internetworks (networks of networks). –This is the key limitation!

9. CISCO NETWORKING ACADEMY Layer 3 solves these problems! Allows device moves through logical addresses. Uses routers to control broadcast propagation. Provides path determination through routing. Uses hierarchical addresses to support world-wide addressing. 3

10. CISCO NETWORKING ACADEMY Logical Order In order to impose logical order on a network, a different kind of address needs to be used. Data Link Layer Physical Layer Network Layer No address Physical Address (Hardware) Logical Address (Software)

11. CISCO NETWORKING ACADEMY Physical v. Logical Address Physical Address –Layer 2 –aka MAC address, hardware address, Ethernet address –burned in card –can’t be changed without changing card –flat scheme (like Social Security Numbers) –Analogy: your name

12. CISCO NETWORKING ACADEMY Physical v. Logical Address Logical Address –Layer 3 –aka protocol address –set by administrator in software –can be easily changed –hierarchical scheme like Phone Numbers (area code, prefix) or ZIP codes –Analogy: your mailing address

13. CISCO NETWORKING ACADEMY Layer 3 addresses Logical or Layer 3 addresses come in different flavors, depending on the layer-3 protocol used: –TCP/IP = IP address –Novell IPX = IPX address –AppleTalk = AT address etc.

14. CISCO NETWORKING ACADEMY Addresses at Layers Data Link Layer Physical Layer Network Layer Session Layer Transport Layer Presentation Layer Application Layer TCP/IP or IPX/SPX or AppleTalk Ethernet MAC address Logical address

15. CISCO NETWORKING ACADEMY Logical Address Composition Though the exact length and format of a logical (layer 3) address differs depending on the protocol, all logical addresses share this basic formula: NETWORK NUMBER HOST NUMBER

16. CISCO NETWORKING ACADEMY Logical Addresses Explained Phone Numbers: 510-723-7464 = Alameda County 510-723-7464 = Hayward Exchange 510-723-7464 = Particular Hayward Phone

17. CISCO NETWORKING ACADEMY Logical Addresses Examples AppleTalk address network 400, host 22 IPX (Novell) network 4b39, host 00c0.4f31.03d2 IP (Internet) network 207.81.104, host 15 400:22 4b39.00c0.4f31.03d2 207.81.104.15

18. CISCO NETWORKING ACADEMY Logical Addresses Explained AppleTalk address network 400, host 22 IPX (Novell) network 4b39, host 00c0.4f31.03d2 IP (Internet) network 207.81.104, host 15 400:22 4b39.00c0.4f31.03d2 207.81.104.15

19. CISCO NETWORKING ACADEMY Logical Addresses Explained AppleTalk address network 400, host 22 IPX (Novell) network 4b39, host 00c0.4f31.03d2 IP (Internet) network 207.81.104, host 15 400:22 4b39.00c0.4f31.03d2 207.81.104.15

20. CISCO NETWORKING ACADEMY Routers Routers: –internetworking devices that work at Layer 3 –understand and use logical addresses –keep tables of information about networks –can make path determinations –don’t normally forward broadcasts –can support multiple layer 3 protocols (TCP/IP, IPX, AppleTalk) at the same time

21. CISCO NETWORKING ACADEMY Routers at work RR RR A Z NETWORK 1NETWORK 2NETWORK 3 NETWORK 4 NETWORK 5NETWORK 6NETWORK 7 Don’t know Z, but I know net #7. Node 1.A is sending to Node 7.Z

22. CISCO NETWORKING ACADEMY The IP Address IP addresses are made up of 32 bits: 10101001110001110100010110001001

23. CISCO NETWORKING ACADEMY Binary IP Addresses In the binary numbering system, each digit has two possible values: 0 or 1

24. CISCO NETWORKING ACADEMY Binary IP Addresses Each value is a binary digit, or bit for short. 01111000 Eight bits together make a unit called a byte. In IP addresses, bytes are called octets (group of eight).

25. CISCO NETWORKING ACADEMY Binary IP Addresses An octet that is all zeros has a decimal value of 0: Binary = 00000000 Decimal = 0

26. CISCO NETWORKING ACADEMY Binary IP Addresses An octet that is all ones has a decimal value of 255: Binary = 11111111 Decimal = 255

27. CISCO NETWORKING ACADEMY Binary IP Addresses In decimal, each place value is a power of ten. We read the number 2342 as two- thousand three-hundred forty-two. 1101001000 2432 10 0 10 1 10 2 10 3

28. CISCO NETWORKING ACADEMY Binary IP Addresses In binary, each place value is a power of two. The octet 11001111 is equivalent to 207 in decimal. 124 111 81632 100 64128 11 2020 21212 2323 2424 2525 2626 2727

29. CISCO NETWORKING ACADEMY Binary IP Addresses The 32 bits of an IP address are grouped into 4 bytes: 10101001110001110100010110001001

30. CISCO NETWORKING ACADEMY IP Addresses We use dotted notation to represent the value of each byte (octet) of the IP address in decimal. 10101001 11000111 01000101 10001001 169 199 69 137

31. CISCO NETWORKING ACADEMY IP Addresses An IP address has two parts: –network number –host number

32. CISCO NETWORKING ACADEMY IP Addresses Which bits refer to the network number? Which bits refer to the host number?

33. CISCO NETWORKING ACADEMY IP Addresses The answers to these questions vary. To find out for a specific address, you need to know how to convert decimal numbers to binary numbers (and back again).