CSEE W4140 Networking Laboratory Lecture 3: IP Forwarding and ICMP Jong Yul Kim 02.04.2009
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CSEE W4140Networking Laboratory
Lecture 3: IP Forwarding and ICMP
Jong Yul Kim02.04.2009
IP in Internet Protocol Stack
NetworkLayer
Link Layer
IP
ARPNetworkAccess
Media
ICMP IGMP
TransportLayer
TCP UDP
Physical
Link
Network
Transport
Application
IP network
10.0.1.11 128.59.16.1
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.”
Today’s topics
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.”
Subnet Exercise 1
Subnet Exercise 2
Netmask
Hosts and routers within a subnet use netmask to determine whether the other host is directly connected or not
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)
prefix
IPv4 Datagram Format (RFC 791)
Router Architecture
Interface Card
Interconnection Network
Interface Card Interface Card
Processor
CPUMemory
Functional Components
Control
Datapath:per-packet processing
forwardingtable
Routingfunctions
IP Forwarding
forwardng tablelookup
forwarding tableupdates
incoming IP datagrams
outgoing IP datagrams
routing protocol
routing protocol
Forwarding Table
Destination Next Hop
10.1.0.0/2410.1.2.0/2410.2.1.0/2410.3.1.0/2420.1.0.0/1620.2.1.0/28
directdirectR4direct R4R4
IP datagrams can be directly delivered (“direct”) or are sent to a router (“R4”)
D e s t i n a t i o n N e x t H o p 1 0 . 1 . 0 . 0 / 2 4 1 0 . 1 . 2 . 0 / 2 4 1 0 . 2 . 1 . 0 / 2 4 1 0 . 3 . 1 . 0 / 2 4 2 0 . 1 . 0 . 0 / 1 6 2 0 . 2 . 1 . 0 / 2 8
d i r e c t R 3 R 3 R 3 R 3 R 3
H 1
R 1 R 2
R 3 R 4
H 2
1 0 . 2 . 1 . 0 / 2 4
2 0 . 1 . 0 . 0 / 1 61 0 . 1 . 2 . 0 / 2 4
1 0 . 1 . 0 . 0 / 2 4 1 0 . 3 . 0 . 0 / 1 6
2 0 . 2 . 1 . 0 / 2 8
2 0 . 2 . 1 . 2 / 2 8
D e s t i n a t i o n N e x t H o p 1 0 . 1 . 0 . 0 / 2 4 1 0 . 1 . 2 . 0 / 2 4 1 0 . 2 . 1 . 0 / 2 4 1 0 . 3 . 1 . 0 / 2 4 2 0 . 1 . 0 . 0 / 1 6 2 0 . 2 . 1 . 0 / 2 8
d i r e c t d i r e c t R 4 d i r e c t R 4 R 4
D e s t i n a t i o n N e x t H o p 1 0 . 1 . 0 . 0 / 2 4 1 0 . 1 . 2 . 0 / 2 4 1 0 . 2 . 1 . 0 / 2 4 1 0 . 3 . 1 . 0 / 2 4 2 0 . 1 . 0 . 0 / 1 6 2 0 . 2 . 1 . 0 / 2 8
R 3 R 3 R 2 d i r e c t d i r e c t R 2
D e s t i n a t i o n N e x t H o p 1 0 . 1 . 0 . 0 / 2 4 1 0 . 1 . 2 . 0 / 2 4 1 0 . 2 . 1 . 0 / 2 4 1 0 . 3 . 1 . 0 / 2 4 2 0 . 2 . 0 . 0 / 1 6 3 0 . 1 . 1 . 0 / 2 8
R 3 d i r e c t d i r e c t R 3 R 2 R 2
D e s t i n a t i o n N e x t H o p 1 0 . 1 . 0 . 0 / 2 4 1 0 . 1 . 2 . 0 / 2 4 1 0 . 2 . 1 . 0 / 2 4 1 0 . 3 . 1 . 0 / 2 4 2 0 . 1 . 0 . 0 / 1 6 2 0 . 2 . 1 . 0 / 2 8
R 1 R 1 d i r e c t R 4 d i r e c t d i r e c t
D e s t i n a t i o n N e x t H o p 1 0 . 1 . 0 . 0 / 2 4 1 0 . 1 . 2 . 0 / 2 4 1 0 . 2 . 1 . 0 / 2 4 1 0 . 3 . 1 . 0 / 2 4 2 0 . 1 . 0 . 0 / 1 6 2 0 . 2 . 1 . 0 / 2 8
R 2 R 2 R 2 R 2 R 2 d i r e c t
to:20.2.1.2
Delivery with forwarding tables
Longest Prefix Matching Rule
Destination Next Hop
11001000 11011111 R2
11001000 00010 R4
11001000 0001011 Direct
Where would this packet go?
Packet destination is: 200.23.146.5111001000 00010111 10010010 00110011
200.223.0.0/16200.16.0.0/13
200.22.0.0/15
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
IOS Command Mode Hierarchy
Read the Introduction part 4 in textbook
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!
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
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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