Sniffter Quick Start Guide
Page 3
Test PC NIC
In addition to testing the network, it is possible to use the Sniffter to test a computer’s NIC (network
interface card). With the
Test PC NIC
menu option, you can check for a network link to the PC, see if the
PC attempts to dynamically acquire an IP address with DHCP, and find out whether the PC responds to
ping packets.
Note that this test will not work if the computer is configured to use a static IP address instead of DHCP.
It may be necessary to connect the cables and start the PC NIC Test on the Sniffter
before
turning on the
computer to test.
The Sniffter requires about 5 seconds to set itself up the first time you
run the PC NIC Test.
The Sniffter displays this screen until there is a physical connection to a
functional, powered PC NIC. Use a crossover Ethernet cable (like the
orange one that ships with the Sniffter) to connect the Sniffter’s network
jack directly to the Ethernet port on the PC’s NIC.
Once link is established (
Link
), the Sniffter waits for the PC to ask for
an IP address via DHCP (the Dynamic Host Configuration Protocol). It
will continue to display
can’t ping PC
until the PC responds to the
Sniffter’s ping packets.
The PC will initially broadcast a “DISCOVER” message, asking for an
IP address from any available DHCP server. The Sniffter emulates a
DHCP server and responds with an offer of 10.0.0.10. When the
Sniffter receives packets from the PC, it will show the PC’s 12-
character MAC address on the last line of the display.
If the PC accepts the DHCP server’s offer, it will request the address.
This screen shows the PC accepting the Sniffter’s offer and requesting
the address. If the display reads
IP REQUEST bad
, then the PC is asking
for a different, incorrect, IP address.
If the PC successfully configures itself with the IP address and starts
responding to the Sniffter’s ping packets, the display will show
PC config
tests good
. The test is complete and the PC should work fine on a
DHCP-based network.
Full Documentation online at http://sniffter.com/support.html
Page 4
Troubleshooting during the PC NIC Test
During the PC NIC Test, the Sniffter will attempt to ping the PC. For additional confirmation, you can
try pinging the Sniffter from the PC. On a Windows PC, bring up a command-line or DOS prompt and
type “ping 10.0.0.2”. If the PC receives responses from the Sniffter (i.e., the pings don’t time out), the
PC’s NIC and Internet (TCP/IP) configuration are good.
You can also try using the winipcfg and ipconfig utilities on Windows PCs to check the status of the
NIC and Internet (TCP/IP) settings.
Symptom
Explanation/Additional Troubleshooting Steps
1
Computer is on but
Sniffter is stuck on the
“Connect network jack”
screen (no link).
Make sure the crossover cable is wired properly (using Sniffter’s Cable
Test).
Make sure the crossover cable connects the Sniffter’s Network jack
(silver, left-hand side of tester) to the PC’s network jack.
Reboot the PC.
Reinstall the PC NIC drivers on the PC.
If possible, try installing a different type of NIC in the PC.
2
Testing doesn’t get past
Waiting for packet
.
Make sure the crossover cable is wired properly (using Sniffter’s Cable
Test).
Reboot the PC.
Check the Internet (TCP/IP) settings on the computer to confirm that it is
configured for DHCP (sometimes referred to as “Acquire an IP address
automatically”).
3
The PC has an IP
address starting with
169.254 (e.g.,
169.254.17.237).
When a computer set with DHCP is unable to contact a DHCP server, it
will default to an IP address on the 169.254.0.0 subnet. Any time a PC
has an address in this range, it has NOT connected to a DHCP server.
Try the troubleshooting steps for Symptom #1.
4
Sniffter displays
IP
REQUEST bad
.
For some reason, the PC is not accepting the Sniffter’s DHCP offers.
Reboot the PC.
If the test never shows
IP REQUEST good
, then there is a problem with the
PC.
5
Sniffter displays
IP
REQUEST good
, but the
ping test fails (
can’t ping
PC
).
The PC might have firewall software installed that blocks ping requests.
Try temporarily disabling the firewall software.
If you can ping the Sniffter from the PC (see instructions above), the PC
configuration is OK.
When the test is complete, turn off the Sniffter, reboot the PC, and reconnect it to the network. If the
network and PC have tested good, the PC should acquire an IP address from network DHCP servers and
be able to connect to your home page and other Internet servers.
