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  #1  
Old 09-13-2018, 06:32 AM
jokerfmj jokerfmj is offline
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Forcing Sessions to specific IPs.

Hello, all.

I was recently upgraded to Windows 10 at work and immediately began having issues with my SecureCRT. Some sessions will not open when typing in their host name and can only be opened by typing their IP address in the "Enter Host" field.

When doing a packet capture I noticed that for some reason SecureCRT is now going to a different IP address on that device when trying to get their via the saved session and that interface does not permit those types of connections. This explains why it is failing. In other SSH/Telnet programs I am able to connect via hostname, but it does take longer than it used to, so they may just be making more DNS queries/attempts to different IPs than SecureCRT does.

I never had this problem with Windows 7, so I am not sure why it would be doing it.

Regardless, it seems that the easiest way to correct the issue would be to tell SecureCRT to open connections for that saved session on a specific IP. However, I cannot find a way to force it to do that. Is there a way to force SecureCRT to load certain hostnames on certain IP addresses?

I have tried deleting and recreating sessions, but I have had no luck thus far.

Thanks.
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  #2  
Old 09-13-2018, 02:37 PM
bgagnon bgagnon is offline
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Hi jokerfmj,
Quote:
When doing a packet capture I noticed that for some reason SecureCRT is now going to a different IP address on that device when trying to get their via the saved session and that interface does not permit those types of connections. This explains why it is failing. In other SSH/Telnet programs I am able to connect via hostname, but it does take longer than it used to, so they may just be making more DNS queries/attempts to different IPs than SecureCRT does.
What do you mean by "different IP address"?

Are you referring to IPv4 vs IPv6?

If so, we have some feature requests that might be appropriate such as "fallback to IPv4 if IPv6 fails".

In the long run, to get it working might take some collaboration between your network, firewall and admin teams. (More information on the "why" behind this behavior might be posted if requested.)

In the meantime:
  1. Run ping localhost in CMD.exe window to show that DNS is resolving to IPv6 addresses (::1 is what's pinged)

  2. Run the following in a CMD:Administrator window:
    reg add "HKLM\System\CurrentControlSet\Services\Tcpip6\Parameters" /v DisabledComponents /t REG_DWORD /d 32 /f
  3. Reboot the Windows machine

  4. Run ping localhost in CMD.exe window to show that DNS is resolving to IPv4 addresses (127.0.0.1 is what's pinged)

  5. Try connecting to SecureCRT saved sessions that failed before taking the above 4 steps
Success?
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Last edited by bgagnon; 09-13-2018 at 03:15 PM.
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  #3  
Old 09-13-2018, 02:47 PM
bgagnon bgagnon is offline
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Hi jokerfmj,

What version of SecureCRT are you using by the way?

This is likely the key piece of info you need if this is an IPv4 vs IPv6 issue.

Changes in SecureCRT 8.1 (Beta 1) -- October 27, 2016
-----------------------------------------------------
  • Hostname resolution now uses the first IP address returned by the system rather than preferring IPv4 over IPv6 addresses.
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  #4  
Old 09-17-2018, 07:10 AM
jokerfmj jokerfmj is offline
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By "Different IP address" I mean the device has about 50 IP addresses configured on it and I want SecureCRT to open a session on the first IP that is returned by the system, but it does not. Instead it is attempting to open a session with the 15th IP address returned by the system. I have verified this through Wiresharck packet captures.

I have added that registry key and have confirmed that "ping localhost" now returns the 127.0.0.1 IP address, but I have the same failed connection result in SecureCRT.

I am running version 7.2.5 build 550.
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  #5  
Old 09-17-2018, 09:04 AM
ekoranyi ekoranyi is offline
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Hi jokerfmj,

To get a better idea of what is happening I would like to review a log of a SecureCRT connection attempt and the resulting packet capture of the DNS query.

Please do not post the log/packet capture to the forums. Please attach them to in email to Support@VanDyke.com with "Attn: Eric Forum post 13250" in the subject line.

Can you take these steps and send me the resulting log file for analysis?

Video Link: https://youtu.be/kzEUhvxKvyY
- Launch SecureCRT and open SecureCRT's main "File" menu and select the "Trace Options" menu item.

- Open the "File" menu again and choose "Log Session..."
--> Specify a path to your Desktop folder and a name of the log file, such as SCRT_Log.txt.

- Now attempt your connection again.

- When the connection fails, open SecureCRT's "File" menu and look at the "Log Session" menu item. If it has a check-mark next to it, click on it to turn off logging.

- Go to your Desktop folder and locate the SCRT_Log.txt file. Please send the SCRT_Log.txt file to me as an attachment to your reply. Please don't paste the contents into the body of your message -- please attach it!
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  #6  
Old 09-17-2018, 12:12 PM
jokerfmj jokerfmj is offline
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See attached.

Last edited by ekoranyi; 09-17-2018 at 12:36 PM.
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  #7  
Old 09-17-2018, 12:53 PM
ekoranyi ekoranyi is offline
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jokerfmj,

In the future please DO NOT attach log files or packet captures directly to your forum post. This can lead to inadvertent exposure of sensitive data to public forums.

Generally when we see:

Code:
0 bytes sent, 0 bytes received
it indicates there is something preventing SecureCRT from reaching the remote host. In most cases it indicates that there is a firewall blocking the connection. Have you ensured that there is not something preventing the connection?

It appears that you/your organization has been working with us via email as well. As we will likely need additional logs I would suggest that we continue troubleshooting via email.
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--Eric

VanDyke Software
Technical Support
support@vandyke.com
(505) 332-5730
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  #8  
Old 09-17-2018, 01:11 PM
jokerfmj jokerfmj is offline
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Quote:
Originally Posted by ekoranyi View Post
jokerfmj,

In the future please DO NOT attach log files or packet captures directly to your forum post. This can lead to inadvertent exposure of sensitive data to public forums.

Generally when we see:

Code:
0 bytes sent, 0 bytes received
it indicates there is something preventing SecureCRT from reaching the remote host. In most cases it indicates that there is a firewall blocking the connection. Have you ensured that there is not something preventing the connection?

It appears that you/your organization has been working with us via email as well. As we will likely need additional logs I would suggest that we continue troubleshooting via email.
We can continue this via email, I have submitted my response to the technician in that thread.

Thank you.
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