notes: Cisco 360 Troubleshooting: Ping

basic ping concepts

test reachability, round trip time, packet loss,

note: rtt includes target processing delay.

- icmp echo is type 8, and icmp echo reply is type 0.
"!" means that the reply was received before the timeout expired
". "means that the reply was not received before the timeout expired.
- default 2 second timeout is configurable.
- default packet size is 100 bytes including the ip header.

ping 172.16.105.1 size 1400


I. to check for serial line problems.

- use extended ping to check for framing and clocking problems

ping 172.16.105.1 data 0000 validate
- sends all zeros as the data portion and check for accurate return data.

ping 172.16.105.1 data FFFF validate
- each hexadecimal F is 1111.
- sends a data pattern of all ones and checks for accurate return data.

ping 172.16.105.1 data AAAA validate
- each hexadecimal A is the binary pattern 1010.
- pattern of alternating ones and zeros and checks for accurate return data.

ping 172.16.105.1 size 1500 repeat 999999999 timeout 0
- timeout of zero - wont wait for reply - also good way to test qos


II. Mark traffic using the TOS Byte

set as an 8-bit decimal or hexadecimal

-multiply ip precedence by 32 to get ToS value
- IP precedence is coded in the most significant 3 bits
- IP precedence 5 is ToS value 160 (10100000)

- multiply DSCP by 4 to get Tos Value
- DSCP is coded in the most significant 6 bits
- DSP 46 is ToS 184 (10111000)

to mark traffic at layer 3

to ping using ip precedence of 5

MCMRTR01#ping
Protocol [ip]:
Target IP address: 172.16.11.1
Repeat count [5]:
Datagram size [100]:
Timeout in seconds [2]:
Extended commands [n]: y
Source address or interface: 172.25.254.1
Type of service [0]: 160
Set DF bit in IP header? [no]:
Validate reply data? [no]:
Data pattern [0xABCD]:
Loose, Strict, Record, Timestamp, Verbose[none]:
Sweep range of sizes [n]:
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.11.1, timeout is 2 seconds:
Packet sent with a source address of 172.25.254.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 260/261/264 ms

for ef packets:

MCMRTR01#ping
Protocol [ip]:
Target IP address: 172.16.11.1
Repeat count [5]:
Datagram size [100]:
Timeout in seconds [2]:
Extended commands [n]: y
Source address or interface: 172.25.254.1
Type of service [0]: 184
Set DF bit in IP header? [no]:
Validate reply data? [no]:
Data pattern [0xABCD]:
Loose, Strict, Record, Timestamp, Verbose[none]:
Sweep range of sizes [n]:
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.11.1, timeout is 2 seconds:
Packet sent with a source address of 172.25.254.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 256/263/276 ms


III. Investigate MTU and fragmentation:

ping 172.16.105.1 size 1501 df-bit

default packet size 100 byes, including 20-byte ip header
try 1500 then 1501

use sweep option with df-bit set
- enter the starting value, ending value and increment between test in bytes


IV. Automate testing with TCL

- tcl or tool command languange is a built-in scripting language
- create a simple script in notepad to ping all of the addresses
-easily capture network ip addresses
show ip alias
press and hold the alt key and drag-select in securecrt
-paste the script into the shell on each router


MCMRTR01(tcl)#foreach address {
+>172.16.11.1
+>172.16.55.1
+>} {ping $address}

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.11.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 260/261/264 ms
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.55.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 120/123/128 ms
MCMRTR01(tcl)#tclquit