rymo's questions

When connecting to a misbehaving SSH server, is there a flag or config setting I can use to tell the client to give up earlier if an interactive console isn't reached in a short period of time?

I am aware of -o ConnectTimeout which will abort the connection when the host is unreachable. In this case, the host is reachable and the initial connection occurs quickly ("Server accepts key" in less than 1s) but then a breakdown in some layer of PAM means I may get an actual command prompt in 3 seconds, 12 seconds, or never. The connection stalls until I send Ctrl+C or wait 90 seconds for "Connection to [host] port 22 timed out"

Until the underlying cause is fixed (which I am not looking to solve with this question), is there anything I can do to mitigate the symptom? I want to automatically disconnect if we don't land at a useful prompt in 5 seconds.

I recently discovered a Windows 7 client that couldn't connect to one of our servers. It turned out the problem was both that the server was set for an MTU of 1514 and that the client was set to 1504.

The server runs CentOS and grep -i MTU /etc/sysconfig/network-scripts/ifcfg* shows nothing. The non-public interface eth1 was still 1500. None of our other machines on the server side have anything other than 1500 for an MTU.

On the client side, there was one other Windows 7 machine in the mix that also had 1504. Taking these machines off-site caused them to work again (but I don't know if that was in spite of the bad MTU, or if the new location caused Windows to select a valid one), but failed once brought back.

1. What would have caused these two Windows machines to have this non-standard MTU setting? How does Windows determine MTU settings?

2. Why would eth0 have had an MTU setting of 1514? How does Linux determine MTU settings?

3. Should I hard-code MTU=1500 into all my ifcfg files from now on for fear that something else will bump it higher? What would override the default of 1500?

I host an e-commerce website for a client who suddenly is unable to access it from his computer. He can ping the server, he can SSH in, but cannot load the website in any browser we've tried: IE, Firefox, Chrome, Opera. Other machines at this location can connect ok. DNS resolves fine, accessing direct with IP address does not work. Using Wireshark on the server side I can see the requests come in, and the responses leave our switch. Wireshark on the client end sees no reply.

Tried so far:

I find nothing in the client's router settings that would block the site for this one computer. He's had his public IP reassigned, and he's tried a different private IP to no avail.

This all seems to point to malware or an otherwise busted Windows 7 install.

The kicker: carry the machine off-site to a different Internet connection, and it works fine. I have never heard of malware that would deny only return responses from one specific server and only while working from a certain public IP address specific physical location (public IP changed, no difference).

In my experience when some sort of filter is the cause, either all the machines behind a single connection would be blocked, or a single machine would be blocked behind all connections. Here it seems neither applies.

What could be the problem? What do we test next?

Update

I noticed the initial redirect to www. was working before the hang, and that the favicon was coming through. Sure enough, both these requests were under 1k and it lead us to check the MTU values on the client and server. But why were they changed?

Is there a Linux utility that can create NTFS symbolic links? That is, a link on an NTFS partition that points to another NTFS folder - one that will work within Windows 7, specifically.

I wish to relocate a folder that is normally in-use while Windows is running. This machine can already dual-boot into Ubuntu, so I'd like to leverage that.

EDIT: To keep this from potentially turning into "which Windows Live CD is best", I will limit this question to "Is it possible with Linux, yes or no?"