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Internet connection issue

Posted on 2006-11-19
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Last Modified: 2013-11-29
I have a computer that is used to connect to internet with no problem, but after ISA server was installed it can not connect to internet anymore.

the question is if I was not told that ISA server was installed, how would I find out the reason why the computer can not connect to internet , which tools should I use or should I have used to find out?

thanks
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Question by:jskfan
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by:dacz
ID: 17975078
get the IP address of your ISA server and make it your proxy server address to have an internet connection.
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by:dacz
dacz earned 35 total points
ID: 17975096
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by:_iskywalker_
_iskywalker_ earned 35 total points
ID: 17975181
first it is nice to know if you have an ip, then if you can ping your host or gateway, then you should contact the admin of the gateway to let you go through the internet. if you can you can ping www.experts-exchange.com and see if  it works, then you can traceroute this address and see which wroute it takes.
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by:jskfan
ID: 17975200
my question was:
 How do I know that it was ISA server  blocking access to internet if I was not told by someone else that ISA server was installed in the computer?



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lrmoore earned 180 total points
ID: 17975330
That depends. Do you mean as a single end-user only - how can you determine that something was blocking your Internet access?
or as a systems administrator, what tools can you use to determine why you can't get Internet access, and could have determined that ISA had been installed somewhere?
or as a systems administrator, what tools can you use to know when something gets installed on one of your servers without you knowing about it?

All of these are really tough questions without simple answers.
Basically, if your Internet access goes down, then start by using the good old 7-layer OSI model, ground up.
Start with Layer1 - check/test all cables, outlets, plugs, etc
Layer2 = protocol checks, vlans, packet errors (duplex mismatch) etc
Layer3 = IP subnets/routes - ping/traceroute/route print/ ipconfig
Layer4 = name resolution/DNS/ firewall rules / proxy rules - Sniffer/Ethereal
Layer5-7 = permissions, credentials and applications. What's wrong with credentials/login? What's new application wise? What changed in any applications? What's different in this system that works and that one that doesn't? Group Policy is new, etc.  Sniffer/Ethereal can help determine these type issues
Layer 8 - 9 = politics, money and religion. Who make the new rules without communicating them to the masses? What governs most changes? Money, politics and religion. (Religion in the way some are religous Microsoft fanatics, some are religously anti-Microsoft fanatics, Cisco fanantics, anti-Cisco fanatics, etc)

None of those tools may ever tell you that it was specifically an unexpected ISA server showing up that was causing the problem. You might determine the IP address/mac-address of whatever it is blocking traffic, then you'd have to manually look at that system to see what was happening.

Do you have a change management process? If you did, then it would never allow that something as potentially disruptive to production as installing ISA could happen without everyone knowing about it. There are other automated tools available to determine and report system changes.
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