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Chabot CollegeChabot College

ELEC 99.08ELEC 99.08ping & traceroute

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ICMPICMP

• ICMP = Internet Control Message Protocol• Layer 3• Part of TCP/IP suite of protocols

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Ethernet

IPARP

ICMP(includes Ping & Traceroute)

TCP(connection-oriented)

FTP:21

HTTP:80

UDP(connectionless)

DNS:53

TFTP:69Layer 7

Layer 4

Layer 3

Layer 1 & 2 FDDIToken Ring

ICMPICMP

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ICMP Echo RequestICMP Echo Request

• Called “ping”• Important network testing tool• Tests connectivity at layers 3-1• Most TCP/IP hosts can send pings

– PCs

– routers

• All TCP/IP hosts will reply to pings (unless configured to discard them for security reasons.)

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DOS Ping DisplayDOS Ping DisplayC:\WINDOWS>ping 172.28.118.1

Pinging 172.28.118.1 with 32 bytes of data:

Reply from 172.28.118.1: bytes=32 time=1ms TTL=255

Reply from 172.28.118.1: bytes=32 time=1ms TTL=255

Reply from 172.28.118.1: bytes=32 time=1ms TTL=255

Reply from 172.28.118.1: bytes=32 time=1ms TTL=255

Ping statistics for 172.28.118.1:

Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),

Approximate round trip times in milli-seconds:

Minimum = 1ms, Maximum = 1ms, Average = 1ms

Key results

Successful replies

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Cisco IOS Ping DisplayCisco IOS Ping Display

• Differs in format from DOS display

• Contains same information

• You’ll work with IOS ping in an upcoming lab.

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ICMP Echo RequestICMP Echo Request

• To check the configuration of layer 3-1 on your PC, you can ping a special internal test address - the loopback address.

• Try it now - – Open a DOS window– >ping 127.0.0.1

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ICMP Echo RequestICMP Echo Request

• To check the configuration of layer 3-1 between your PC and another host, you can ping that host’s address.

• Try it now - – Open a DOS window– >ping 172.28.118.10

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ICMP Echo RequestICMP Echo Request

• You can also use hostnames in the ping command (if DNS is running, or host tables are enabled).

• Try it now - – Open a DOS window– >ping academy1

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TracerouteTraceroute

• Tool used to trace path from source to destination host.

• TCP/IP not designed for traceroute, so it is sometimes unpredictable.

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Traceroute PacketsTraceroute Packets

• Most traceroute programs, including the Cisco IOS traceroute, send UDP packets (User Datagram Protocol).

• Micrososft tracert sends ICMP echo request (ping) packets.

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Traceroute CommandTraceroute Command

• Unix: traceroute• Cisco IOS: traceroute (trace)• DOS: tracert

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Traceroute OperationTraceroute Operation

• Transmits packets with small Time-To-Live (TTL) values.– First packets have TTL = 1– Second have TTL = 2– Third have TTL = 3– etc.

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Time to Live FieldTime to Live Field

TTL

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Traceroute OperationTraceroute Operation• Generates messages from each router used along

the path.• Every router that handles a packet subtracts one from

the packet's TTL. If the TTL reaches zero, the packet has expired and is discarded.

• At that point, most routers send an ICMP Time Exceeded message back to the sender - traceroute uses this message.

• A TTL value of one should produce a message from the first router; two from the second; etc.

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Traceroute OperationTraceroute Operation

Sender Target

TTL = 1 TTL = 2 TTL = 3 TTL = 4

Traceroute returns these IP addresses& hostnames (via reverse lookup)

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Traceroute DocumentationTraceroute Documentation

• Cisco has documented the operation and use of traceroute at http://www.cisco.com/warp/public/105/traceroute.shtml

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DOS Traceroute DisplayDOS Traceroute DisplayC:\WINDOWS>tracert www.husd.k12.ca.us

Tracing route to www.husd.k12.ca.us [206.110.193.5]

over a maximum of 30 hops:

1 1 ms 1 ms 1 ms 192.168.0.1

2 23 ms 32 ms 32 ms adsl-63-198-176-254.dsl.snfc21.pacbell.net [63.198.176.254]

3 20 ms 19 ms 21 ms core4-g3-0.snfc21.pbi.net [216.102.187.130]

4 20 ms 19 ms 19 ms ded2-fa12-0-0.snfc21.pbi.net [209.232.130.5]

5 25 ms 51 ms 21 ms vip-Alameda-Co.cust-rtr.pacbell.net [216.102.184.2]

6 44 ms 37 ms 43 ms 206.110.252.174

7 47 ms 40 ms 40 ms www.husd.k12.ca.us [206.110.193.5]

Trace complete.

Round trip timeHop Router

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DOS TracerouteDOS Traceroute

• Try it now - – Open a DOS window:– >tracert porter– >tracert www.husd.k12.ca.us

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Cisco IOS Traceroute DisplayCisco IOS Traceroute Display

• Differs in format from DOS display

• Contains same information

• You’ll work with IOS trace in an upcoming lab.

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Cisco IOS TracerouteCisco IOS Traceroute

• Try it now - – Start Router e-SIM– Give all your routers a configuration:

• click SHOW DONE

• in the row of SET buttons at the bottom, click A, B, C, D, E

• click HIDE DONE

– Login - Password - cisco

– Lab_A> trace Lab_E– Lab_A> trace 210.93.105.2– click SHOW TOPOLOGY and compare to the trace results...