1

7

Ping Program

2

7

Introduction - Problem

How do I know if a host is reachable?

3

7

ICMP echo request / reply

Type ( 0 or 8 ) code ( 0 ) checksum

Optional data

0 7 8 15 16 31

identifier Sequence number

Ping program uses :

ICMP echo request (type 8)

ICMP echo reply (type 0)

4

7

Ping 131.107.7.29

IP Address = 131.107.7.28 IP Address = 131.107.7.293333

ICMP Reply

2222

1111

ping 131.107.7.29ping 131.107.7.29

ICMP Request

5

7

Ping output

D:\>ping www.cisco.com

Pinging cio-sys.cisco.com [192.31.7.130] with 32 bytes of data:

Reply from 192.31.7.130: bytes=32 time=190ms TTL=239

Reply from 192.31.7.130: bytes=32 time=180ms TTL=239

Reply from 192.31.7.130: bytes=32 time=180ms TTL=239

Reply from 192.31.7.130: bytes=32 time=180ms TTL=239

( Success rate is 100 percent (5/5), round-trip min/avg/max = 192/192/192ms ) (0% packet loss)

6

7

Ping options

Usage: ping [-t] [-a] [-n count] [-l size] [-f] [-i TTL] [-v TOS] [-r count] [-s count]

[[-j host-list] | [-k host-list]] [-w timeout] destination-list

Options:

-t Ping the specifed host until interrupted.

-a Resolve addresses to hostnames.

-n count Number of echo requests to send.

-l size Send buffer size.

-f Set Don't Fragment flag in packet.

-i TTL Time To Live.

-v TOS Type Of Service.

-r count Record route for count hops.

-s count Timestamp for count hops.

-j host-list Loose source route along host-list.

-k host-list Strict source route along host-list.

-w timeout Timeout in milliseconds to wait for each reply.

7

7

Exercise: Find out about the PING options