Testing elusive network problems

In the past, I’ve had quite a few customers that have ‘mysterious’ network issues in their environment. In most cases, they are elusive and difficult to track down. Seriously, it could be anything from old wiring to a faulty switch to a bad network card, etc. The first step is to create a batch file to run at the command prompt to isolate the issue. I tend to run this from each of the machines. Once I’ve executed this, I’ll break out our Test-Um network Kit (http://www.test-um.com/validator/ ) and get serious about isolating the problem.

I've copied a sample run from my network below. Here's
the rundown. Feel free to substitute your addresses in
and run the pings on your network.

Step 1 pings 127.0.0.1 to make sure your network stack
is working. If this is hosed it's most likely a
Windows problem

Step 2 pings the LAN interface of my local machine.
This should show that the adaptor is up and working.
It may be disconnected or have other problems, tho.

Step 3 pings another machine on the local network.
Tests the hub/switch, isolates for possible server
problem.

Step 4 tests the local/backend interface of the
server. If step 3 is ok then look for a bad switch
port, cable to server, other network gear in the way,
or NIC on server.

Step 5 tests local naming.

Step 6 tests the front-end/Internet connection of your
SBS server or other router. This isolates the
connection to your dsl/cable/t1/ oc3 internet
connection.

Step 7 tests internet by IP address, isolating for DNS
problems. 4.2.2.1 is verizon/genuity/ level3/whoever
they are now's public DNS servers.

Step 8 tests for named connection to internet by
pinging google.

Here's output from a similar script on my network:

STEP 1: localhost/network stack
C:\Windows\system32 >ping 127.0.0.1

Pinging 127.0.0.1 with 32 bytes of data:

Reply from 127.0.0.1: bytes=32 time<1ms ttl="128" bytes="32" ttl="128" bytes="32" ttl="128" bytes="32" ttl="128" sent =" 4," received =" 4," lost =" 0" minimum =" 0ms," maximum =" 0ms," average =" 0ms">ping 192.168.9.118

Pinging 192.168.9.118 with 32 bytes of data:

Reply from 192.168.9.118: bytes=32 time<1ms ttl="128" bytes="32" ttl="128" bytes="32" ttl="128" bytes="32" ttl="128" sent =" 4," received =" 4," lost =" 0" minimum =" 0ms," maximum =" 0ms," average =" 0ms">ping 192.168.9.50

Pinging 192.168.9.50 with 32 bytes of data:

Reply from 192.168.9.50: bytes=32 time=2ms TTL=64
Reply from 192.168.9.50: bytes=32 time=2ms TTL=64
Reply from 192.168.9.50: bytes=32 time=2ms TTL=64
Reply from 192.168.9.50: bytes=32 time=2ms TTL=64

Ping statistics for 192.168.9.50:
Packets: Sent = 4, Received = 4, Lost = 0 (0%
loss),
Approximate round trip times in milli-seconds:
Minimum = 2ms, Maximum = 2ms, Average = 2ms

STEP 4: SBS be
C:\Windows\system32 >ping 192.168.9.101

Pinging 192.168.9.101 with 32 bytes of data:

Reply from 192.168.9.101: bytes=32 time=3ms TTL=128
Reply from 192.168.9.101: bytes=32 time=2ms TTL=128
Reply from 192.168.9.101: bytes=32 time=2ms TTL=128
Reply from 192.168.9.101: bytes=32 time=2ms TTL=128

Ping statistics for 192.168.9.101:
Packets: Sent = 4, Received = 4, Lost = 0 (0%
loss),
Approximate round trip times in milli-seconds:
Minimum = 2ms, Maximum = 3ms, Average = 2ms

STEP 5: SBS by name
C:\Windows\system32 >ping lilbro

Pinging lilbro.CharlandGrap hics.local [192.168.9.101]
with 32 bytes of data:

Reply from 192.168.9.101: bytes=32 time=1ms TTL=128
Reply from 192.168.9.101: bytes=32 time=63ms TTL=128
Reply from 192.168.9.101: bytes=32 time=2ms TTL=128
Reply from 192.168.9.101: bytes=32 time=1ms TTL=128

Ping statistics for 192.168.9.101:
Packets: Sent = 4, Received = 4, Lost = 0 (0%
loss),
Approximate round trip times in milli-seconds:
Minimum = 1ms, Maximum = 63ms, Average = 16ms

C:\Windows\system32 >

STEP 6: SBS fe
C:\Windows\system32 >ping 24.177.54.186

Pinging 24.177.54.186 with 32 bytes of data:

Reply from 24.177.54.186: bytes=32 time=15ms TTL=128
Reply from 24.177.54.186: bytes=32 time=36ms TTL=128
Reply from 24.177.54.186: bytes=32 time=2ms TTL=128
Reply from 24.177.54.186: bytes=32 time=2ms TTL=128

Ping statistics for 24.177.54.186:
Packets: Sent = 4, Received = 4, Lost = 0 (0%
loss),
Approximate round trip times in milli-seconds:
Minimum = 2ms, Maximum = 36ms, Average = 13ms

C:\Windows\system32 >

STEP 7: outside by IP
C:\Windows\system32 >ping 4.2.2.1

Pinging 4.2.2.1 with 32 bytes of data:

Reply from 4.2.2.1: bytes=32 time=27ms TTL=248
Reply from 4.2.2.1: bytes=32 time=17ms TTL=248
Reply from 4.2.2.1: bytes=32 time=16ms TTL=248
Reply from 4.2.2.1: bytes=32 time=17ms TTL=248

Ping statistics for 4.2.2.1:
Packets: Sent = 4, Received = 4, Lost = 0 (0%
loss),
Approximate round trip times in milli-seconds:
Minimum = 16ms, Maximum = 27ms, Average = 19ms

STEP 8: Outside by name
C:\Windows\system32 >ping news.google. com

Pinging news.l.google. com [64.233.179. 104] with 32
bytes of data:

Reply from 64.233.179.104: bytes=32 time=73ms TTL=239
Reply from 64.233.179.104: bytes=32 time=94ms TTL=239
Reply from 64.233.179.104: bytes=32 time=115ms TTL=239
Reply from 64.233.179.104: bytes=32 time=136ms TTL=239

Ping statistics for 64.233.179.104:
Packets: Sent = 4, Received = 4, Lost = 0 (0%
loss),
Approximate round trip times in milli-seconds:
Minimum = 73ms, Maximum = 136ms, Average = 104ms

C:\Windows\system32 >