Network layer  Basic routing
OSI model <ul><li>Network layer
How to connect different subnets
Logical addressing </li></ul>
Routers and subnets <ul><li>What is </li><ul><li>A router?
A subnet?
Logical addresses </li></ul><li>Switches are for later </li></ul>
Connection through routers
Routers and subnets How does packet go from PC A to B?
Inside a router
Routing tables <ul><li>Routing table on windows </li><ul><li>“route print” </li></ul><li>Routing table on my linux box </l...
SOHO network example <ul><li>What is needed for this network? </li></ul><ul><li>DHCP, NAT, IP, netmask addresses, gateway....
Exercise <ul><li>What is DHCP? </li><ul><li>Look it up. </li></ul><li>Use Wireshark to find DHCP packets. </li><ul><li>Wha...
Does it correspond to your network settings? </li></ul></ul>
Internet protocol <ul><li>Old protocol </li><ul><li>Like UDP and TCP </li></ul><li>Make sure you know how TCP/IP works. </...
IP addresses The IP address for the eth0 interface Broadcast is a reserved address. Used to send to all hosts on subnet Su...
Exercise <ul><li>Find the IP information for your PC </li><ul><li>Which interface is active?
Find the subnet IP range
How many IP addresses does it cover
DNS server? Default gateway </li></ul></ul>
Network configuration <ul><li>Always use DHCP </li><ul><li>Except (maybe) for servers </li></ul><li>DHCP allows centralize...
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ITET1 Routing Network layer.odp

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ITET1 Routing Network layer.odp

  1. 1. Network layer Basic routing
  2. 2. OSI model <ul><li>Network layer
  3. 3. How to connect different subnets
  4. 4. Logical addressing </li></ul>
  5. 5. Routers and subnets <ul><li>What is </li><ul><li>A router?
  6. 6. A subnet?
  7. 7. Logical addresses </li></ul><li>Switches are for later </li></ul>
  8. 8. Connection through routers
  9. 9. Routers and subnets How does packet go from PC A to B?
  10. 10. Inside a router
  11. 11. Routing tables <ul><li>Routing table on windows </li><ul><li>“route print” </li></ul><li>Routing table on my linux box </li></ul>(Using “route -n” instead of “ip route show table all” for readability)
  12. 12. SOHO network example <ul><li>What is needed for this network? </li></ul><ul><li>DHCP, NAT, IP, netmask addresses, gateway. </li></ul>
  13. 13. Exercise <ul><li>What is DHCP? </li><ul><li>Look it up. </li></ul><li>Use Wireshark to find DHCP packets. </li><ul><li>What do they contain?
  14. 14. Does it correspond to your network settings? </li></ul></ul>
  15. 15. Internet protocol <ul><li>Old protocol </li><ul><li>Like UDP and TCP </li></ul><li>Make sure you know how TCP/IP works. </li></ul>
  16. 16. IP addresses The IP address for the eth0 interface Broadcast is a reserved address. Used to send to all hosts on subnet Subnet mask is used with IP address to determine the subnet IP range Default route is another word for default gateway. Used when sending to hosts outside the local subnet Primary DNS is the server to ask when translating from exmaple.com to an IP address OSI layers 1 and 2
  17. 17. Exercise <ul><li>Find the IP information for your PC </li><ul><li>Which interface is active?
  18. 18. Find the subnet IP range
  19. 19. How many IP addresses does it cover
  20. 20. DNS server? Default gateway </li></ul></ul>
  21. 21. Network configuration <ul><li>Always use DHCP </li><ul><li>Except (maybe) for servers </li></ul><li>DHCP allows centralized administration. </li></ul>
  22. 22. DHCP in action Note the difference between first request and subsequent requests
  23. 23. Internet control message protocol <ul><li>Examples </li><ul><li>Echo request
  24. 24. Echo reply
  25. 25. Destination host unreachable
  26. 26. TTL expired </li></ul></ul>
  27. 27. ICMP exercise <ul><li>Ping </li><ul><li>Do a ping request to a local existing IP
  28. 28. Do a ping request to a local non-existing IP </li></ul><li>Traceroute </li><ul><li>What is traceroute?
  29. 29. Traceroute google.com
  30. 30. Traceroute sde.dk </li></ul></ul>Use wireshark to check requests and responses
  31. 31. Multiple routers <ul><li>What is required for PC A to talk to PC B?
  32. 32. Hint: </li><ul><li>It is all about routing tables. </li></ul></ul>
  33. 33. Manual configuration <ul><li>“ip route add 192.168.55.0/24 via 192.168.1.254 dev eth1”
  34. 34. Simple.
  35. 35. Why not do it manually: </li><ul><li>New subnet address
  36. 36. Subnet on different device
  37. 37. Many subnets makes this important issues </li></ul></ul>
  38. 38. Router autoconfiguration <ul><li>Two options </li><ul><li>Link-state </li><ul><li>Each router has a complete routing table, i.e. a complete image of the network </li></ul><li>Distance vector </li><ul><li>Router only retains keep a distance table with dst network, next router and distance (e.g. hop count) </li></ul></ul><li>Implementations </li><ul><li>OSPF (link-state)
  39. 39. RIP (Distance vector) </li></ul></ul>
  40. 40. IGP and EGP IGP (using RIP or OSPF) EGP (using BGP)
  41. 41. Border gateway protocol <ul><li>Live demo! </li><ul><li>Start here
  42. 42. Choose a server an telnet to it
  43. 43. “sho ip bgp summary”
  44. 44. “sho ip ngp <IP>” </li></ul></ul>

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