Best practice for resolving connectivity issues 1

[pbunyon]

What is the best practice in troubleshooting intranet access versa's internet access within an enterprises network?
Tracert seems to alway error out at proxy/ISA/firewall within an intranet when trying a trace on yahoo or any other accesable sites from within intranet.
Can I assume this test validates connectivity to the internet or not?
Or is the ICMP packets merely being blocked?
Any help is appreciated.


Paul

 

[mbrooks]

1. ping
2. tracert
3. check to see if the network cable is plugged in



M. Brooks

http://mbrooks.info

 

[Jamesfg02]

Try ping a public address by the public ip, like yahoo 216.109.112.135. That will tell you if you have ip connectivity.

Do an ipconfig and try to ping another workstation on the lan. That will tell you if you can talk to another pc on the lan.

 

[pansophic]

In all probability your ICMP packets are being blocked at the firewall, therefore the traceroute failure at the ISA server. You could turn this rule off, as an outbound ICMP request is normally not a security issue, nor is an inbound ICMP reply. But for some reason, most default rulesets block ICMP in both directions.

If you are *nix literate you can use hping to test connectivity over TCP, UDP or ICMP as your needs dictate. That will allow you to test Internet connectivity within the firewall ruleset.

And no, you cannot assume connectivity to the Internet unless you can get a host out there to respond to your packets. The fact that you get no responses or blocked responses when Internet connectivity works does not correspond to no responses or blocked responses means that the Internet connectivity is up (if that blocking is occuring at your firewall).

You can usually telnet to a web server at port 80 to determine if connectivity is up. Normally you would want to do this both by name and by IP address because it is possible that your connectivity is up, but your DNS server is not (or is busy). They are two completely different problems that will frequently yield the same result.


pansophic