Transcript Chabot College ELEC 99.08 ping & traceroute CISCO NETWORKING ACADEMY ICMP • ICMP = Internet Control Message Protocol • Layer 3 • Part of TCP/IP suite.

Chabot College
ELEC 99.08
ping & traceroute
CISCO NETWORKING ACADEMY
ICMP
• ICMP = Internet Control Message Protocol
• Layer 3
• Part of TCP/IP suite of protocols
CISCO NETWORKING ACADEMY
ICMP
Layer 7
Layer 4
FTP
HTTP
DNS
TFTP
:21
:80
:53
:69
TCP
UDP
(connection-oriented)
(connectionless)
ICMP
Layer 3
Layer 1 & 2
CISCO NETWORKING ACADEMY
ARP
Token Ring
IP
Ethernet
(includes Ping & Traceroute)
FDDI
ICMP 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.)
CISCO NETWORKING ACADEMY
DOS Ping Display
C:\WINDOWS>ping 172.28.118.1
Pinging 172.28.118.1 with 32 bytes of data:
Successful replies
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
Key results
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
CISCO NETWORKING ACADEMY
Cisco IOS Ping Display
• Differs in format from DOS display
• Contains same information
• You’ll work with IOS ping in an
upcoming lab.
CISCO NETWORKING ACADEMY
ICMP 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
CISCO NETWORKING ACADEMY
ICMP 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
CISCO NETWORKING ACADEMY
ICMP 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
CISCO NETWORKING ACADEMY
Traceroute
• Tool used to trace path from source to
destination host.
• TCP/IP not designed for traceroute, so it is
sometimes unpredictable.
CISCO NETWORKING ACADEMY
Traceroute Packets
• Most traceroute programs, including the
Cisco IOS traceroute, send UDP packets
(User Datagram Protocol).
• Micrososft tracert sends ICMP echo request
(ping) packets.
CISCO NETWORKING ACADEMY
Traceroute Command
• Unix: traceroute
• Cisco IOS: traceroute (trace)
• DOS: tracert
CISCO NETWORKING ACADEMY
Traceroute Operation
• Transmits packets with small Time-ToLive (TTL) values.
– First packets have TTL = 1
– Second have TTL = 2
– Third have TTL = 3
– etc.
CISCO NETWORKING ACADEMY
Time to Live Field
TTL
CISCO NETWORKING ACADEMY
Traceroute 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.
CISCO NETWORKING ACADEMY
Traceroute Operation
Traceroute returns these IP addresses
& hostnames (via reverse lookup)
Sender
Target
TTL = 1
CISCO NETWORKING ACADEMY
TTL = 2
TTL = 3
TTL = 4
Traceroute Documentation
• Cisco has documented the operation and use
of traceroute at
http://www.cisco.com/warp/public/105/traceroute.shtml
CISCO NETWORKING ACADEMY
DOS Traceroute Display
C:\WINDOWS>tracert www.husd.k12.ca.us
Hop
Tracing route to www.husd.k12.ca.us [206.110.193.5]
over a maximum of 30 hops:
Round trip time
1 1 ms 1 ms
2 23 ms 32 ms
3 20 ms 19 ms
4 20 ms 19 ms
5 25 ms 51 ms
6 44 ms 37 ms
7 47 ms 40 ms
Trace complete.
CISCO NETWORKING ACADEMY
1 ms
32 ms
21 ms
19 ms
21 ms
43 ms
40 ms
Router
192.168.0.1
adsl-63-198-176-254.dsl.snfc21.pacbell.net [63.198.176.254
core4-g3-0.snfc21.pbi.net [216.102.187.130]
ded2-fa12-0-0.snfc21.pbi.net [209.232.130.5]
vip-Alameda-Co.cust-rtr.pacbell.net [216.102.184.2]
206.110.252.174
www.husd.k12.ca.us [206.110.193.5]
DOS Traceroute
• Try it now – Open a DOS window:
– >tracert porter
– >tracert www.husd.k12.ca.us
CISCO NETWORKING ACADEMY
Cisco IOS Traceroute Display
• Differs in format from DOS display
• Contains same information
• You’ll work with IOS trace in an
upcoming lab.
CISCO NETWORKING ACADEMY
Cisco 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...
CISCO NETWORKING ACADEMY