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CSEE W4140 Networking Laboratory

CSEE W4140 Networking Laboratory. Lecture 3: IP Forwarding and ICMP Jong Yul Kim 02.04.2009. Application. Transport. Network. Link. Physical. IP in Internet Protocol Stack. IP network. 10.0.1.11. 128.59.16.1. Two functions of network layer. Routing

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CSEE W4140 Networking Laboratory

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  1. CSEE W4140Networking Laboratory Lecture 3: IP Forwarding and ICMP Jong Yul Kim 02.04.2009

  2. Application Transport Network Link Physical IP in Internet Protocol Stack

  3. IP network 10.0.1.11 128.59.16.1

  4. Two functions of network layer • Routing “Collective interactions of all routers to determine the paths that packets take on their trips from source to destination” • Forwarding “The transfer of a packet from an incoming link to an outgoing link within a single router.”

  5. Today’s topics

  6. Subnet (RFC 950) • Hard to define… • General recipe “Detach each interface from its host or router, creating islands of isolated networks, with interfaces terminating the end points of the isolated networks.Each of these isolated networks is called a subnet.”

  7. Subnet Exercise 1

  8. Subnet Exercise 2

  9. Netmask • Hosts and routers within a subnet use netmask to determine whether the other host is directly connected or not

  10. prefix Classless Interdomain Routing(RFC 4632) • Examples • 128.59.19.10  One host on CS net • 128.59.16.0/21  CS wired net • 128.59.0.0/16  Columbia wired net • Two parts to an address • Network part (first 21 bits of CS wired) • Host part (remaining 11 bits)

  11. IPv4 Datagram Format (RFC 791)

  12. Router Architecture

  13. Functional Components Control Datapath: per-packet processing

  14. Forwarding Table IP datagrams can be directly delivered (“direct”) or are sent to a router (“R4”)

  15. Delivery with forwarding tables to:20.2.1.2

  16. Longest Prefix Matching Rule 200.223.0.0/16 200.16.0.0/13 200.22.0.0/15 • Where would this packet go? Packet destination is: 200.23.146.51 11001000 00010111 10010010 00110011

  17. ICMP (RFC 792) • Used to communicate network info • Error reporting • Router advertisement and discovery • Has type and code • Type 8, code 0 = echo request • Type 0, code 0 = echo reply • Replies have original sender’s IP header + 64 bits of data • Used by • ping • traceroute

  18. IOS Command Mode Hierarchy Read the Introduction part 4 in textbook

  19. Main Points of Lab 3 • Setting up static routes on: • Linux machines • Cisco routers • Routing packets using: • Proxy ARP • ICMP Route Redirect • Netmasks Kermit not used  use picocom!

  20. Homework • Prelab 3 due on Friday (02.06.2009) • Lab report 2 due by beginning of lab 3 next week • Read • RFC 2453 “RIP Version 2” parts 1 ~ 3

  21. Announcements • In-class quiz next week • Basic ARP, subnets, and IP forwarding • Swipe Access • Apar, Hai, Eric, Aaron, Abhinav • Please check on Monday

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