Re: [cobalt-users] Strange IP Problem

[Gareth Bromley <gbromley@xxxxxxxxxxx>]

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Ethos Subscriptions wrote:
| We recently changed the ADSL provider we use at our office, and
through our
| new connection we can't properly access our server.
First thing I'd ask/check is, have all your access control/security
controls been updated to allow this new IP range through?

| The server has a main IP address used for all services, and a
secondary IP
| address which has only a couple of sites assigned to it.
| <IP ADDRESS 1> - main IP address. We can ping and traceroute this
address,
| but NOT access web sites, email, SSH or Telnet through it. This is our
| primary nameserver address.
| <IP ADDRESS 2> - second IP address. We can ping and traceroute this
address,
| and access the mail server, SSH and Telnet. We have only a couple of web
| sites set up at this IP address, but we can access them fine. This
is our
| secondary nameserver address.
This sounds awfully like firewalling issue on the local machine, or
maybe upstream at the provider.

| We get the above problem when accessing the Internet through our ADSL
| connection. However, our ADSL provider also offers us dial-up access
- - when
| we dial up to our account through a standard modem, there is no problem.
I take it the differences are IP address only? If web traffic is the
only thing affected I'd check that the provider is/isnt using WCCP
caching, however in you case you cant seem to get to any applications.


| Anyone have any ideas what's going on? Our ADSL connection appears to
| function flawlessly apart from this problem. We seem to be able to
access
| other web sites, including sites located on servers in the same data
centre.
As above, I'd say OS/application level firewall issue on the box?

| A client of ours reported the same problem a few months ago with a
different
| ISP, and it was never resolved. Our ISP is looking into it, but is
having
| difficulty locating a problem as they can access the server with no
problems
| at their office. To us, it sounds like there is a block being put on <IP
| ADDRESS 1> - but could it be a problem with the RaQ? If so what do
you think
| it is? If not, any ideas what the problem could be or tips on how we can
| further investigate?
Investigation is easy using tools like:
- - ping to test network connectivity
- - traceroute to see where the traffic fails
- - tcptraceroute to see what the failure is caused by i.e. firewall

Hope this helps,
- --
- --Gareth Bromley
CCIE Candidate CCDP CCNP CSS1 CCIP Security
CCSA CCSE NSA RHCE SCSA SCNA CISSP

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