SSH/TELNET

Fine-Tune SSH/telnet CLI Parameters

The IP Fabric's discovery is primarily using Command Line Interface (CLI) to discover network elements. There are certain default CLI parameters that can be found in Settings → Advanced → SSH/TELNET.

Network Device Login Timeout

Timeout before the logging prompt is received. It may take longer for remote branches over low-speed lines, or destined to overloaded devices.

Network Device Session Timeout

Too many Command Timeout errors during the Discovery process may indicate that Network device session timeout is too short and it may be necessary to expect a delay for a response to arrive.

Maximum Number Of Parallel Sessions

To prevent flooding your network with too many SSH/TELNET sessions set Maximum number of parallel sessions. This setting can be also helpful if the AAA server (TACACS/Radius) has a limit of parallel AAA requests for users.

In rare cases, the Cisco ISE or similar systems may rate limit the command authorization. When there are too many authorization failures and Cisco ISE is in place, try to limit the number of parallel sessions down to 10 and steadily increase.

Basic Failure

How many times to retry a connection for any error, except authentication failure.

Authentication Failure

Authentication failure can occur even if a user is authorized to login but may happen, for example, when an AAA server is overloaded or an authentication packet is lost.

Command Authorization Failure Retries

If you see many examples of Authentication error during the Discovery process, please adjust Authentication failure and Command Authorization Failure retries.

Example Of Error Message In Connectivity Report

According to the summary of issues in the very first completed snapshot, the CLI Settings can be adjusted. Here are some of the most common errors and adjustments:

Error	Error Type	How To Mitigate
connect ETIMEDOUT XX.XX.XX.XX:22	Connection error	Received no response from the destination.
connect ECONNREFUSED XX.XX.XX.XX:22	Connection error	The connection to the destination is being blocked by an access-list or firewall.
All configured authentication methods failed	Authentication error	Unable to authenticate to the destination host
Authentication failed	Authentication error	Unable to authenticate to the destination host
Authentication failed - login prompt appeared again	Authentication error	Unable to authenticate to the destination host
SSH client not received any data for last 120000 ms! cmd => show vrrp  | e #^$	Command timeout	The command 'show vrrp  | e #^$' timed out. Increase device session timeout.
Can't detect prompt	Command timeout	Unable to detect CLI prompt. Increase network device login timeout.
Command "enable" authorization failed, tried 2x	Command authorization failure	The command wasn't authorized. Increase command authorization failure retries or increase the timer value (ms)

Setting Up Jumphost

Jumphost allows to set-up connection to the server which can be used as a proxy server for discovery purposes. IP Fabric uses an ssh connection to the jumphost server and python on the client and server side.

Python version on the jumphost
2.7	supported
3.5	supported
3.6	supported
3.7	supported
3.8	unsupported
3.9	unsupported

Warning

Please bear in mind, that once the connection is established, it will be enabled permanently, until disabled or removed! If there are any network issues, IP Fabric software will try to establish a connection periodically.

Important

At least one seed IP address has to be provided as a starting point behind Jumphost in seed configuration.

Adding New Jumphost

1. Open jumphost settings, using item Settings → Advanced → SSH/TELNET

2. At the bottom of the page, please select + Add button

   

3. Fill in all necessary data

   1. Label - the name for configuration (mandatory)
   2. Jump host Address - IP address of FQDN name (mandatory)
   3. IPv4 subnets - subnet in CIDR representation, allows adding more than open, separated with spaces (mandatory)
   4. Exclude IPv4 subnets - subnet to exclude in CIDR representation, allows to add more than open, separated with spaces (optional)
   5. Login type
      1. Use credentials - require to provide username and password
      2. Use SSH keys - if you copied ssh public key to the proxy server, it won’t require providing a password (please jump to the SSH key configuration section)
   6. Username - Username for authentication (mandatory)
   7. Password - password for authentication (mandatory if ‘Use credentials’ is used) i.e., refer to the picture below

4. Click + Add button

5. If a connection is open, you will see the Running status in Jumphost list

   

Warning

If you use 0.0.0.0/0 or another subnet that includes your network from which you are connecting to IP Fabric, make sure you put your network to "Exclude IPv4 subnet". Otherwise, your IP connection will be lost and you will have to recover from the console.

SSH Key Configuration

Info

Adding ssh key to proxy server allows you to avoid using passwords for authentication

1. Download ssh key from Jumphost settings

   

2. Save jumphost-public-key.pub

3. Copy file content to authorized_keys file of the user that will authenticate with Jumphost server. Please follow official documentation at https://www.ssh.com/ssh/authorized-key

4. Restart sshd service to apply settings

5. If the key has been copied you can use the option ‘Use SSH keys' while adding a new Jumphost server, instead of 'Use credentials’

Disabling Jumphost Connection

1. Edit configuration that needs to be disabled, i.e.\

   

2. Change the setting to Disabled,

3. Click the Update button

   

Remove Jumphost Configuration

1. On Jumphost servers list, check configuration that needs to be removed

2. Click Delete button

   

Discovery With Jumphost Issues

Only TCP connections work through the Jump host. Traceroute with ICMP is not supported so the discovery process might not be able to get over the unreachable part of the network (for example sites separated by the provider’s network). In this case, you will have to add at least one IP from each site to the seeds settings.

Custom SSH/Telnet Ports

Info

Custom SSH/Telnet ports settings enable the discovery process to use different than standard ports for connecting. The standard for SSH is port 22 and 23 for Telnet.

In the following example we configure the discovery process to use port 8080 for SSH connections to 192.168.168.10:

As a result of such configuration, we would create a new item under the Custom SSH/Telnet ports configuration, which will be applied to every new snapshot created by IP Fabric.

Telnet/SSH URL Handler On MS Windows 7 And Later

If you want to be able to connect directly to a device from the IP Fabric web interface, you need to register a Telnet/SSH URL handler. You will be touching Windows Registry, please be sure, that you know what you are doing, have appropriate backups and are comfortable in doing so.

Backup Windows Registry

1. Click Start, type regedit.exe in the search box, and then press Enter
2. In Registry Editor, click File → Export
3. In the Export Registry File box, select the location where you want to save the backup copy, name your back up file and click Save

Putty

Download Putty

1. Go to https://www.chiark.greenend.org.uk/~sgtatham/putty/latest.html
2. Download Putty
3. This tutorial expects Putty in C:\Program Files (x86)\putty.exe

Register Telnet/SSH URL Handler

1. Go to https://gist.github.com/sbiffi/11256316
2. Download putty.reg file
3. Edit path to Putty if differs from C:\Program Files (x86)\putty.exe
4. Download putty.vbs (save it to C:\putty.vbs or change this path in putty.reg above)
5. Edit path to Putty if differs from C:\Program Files (x86)\putty.exe
6. Launch putty.reg to associate ssh:// and telnet:// to this script

SecureCRT

Download SecureCRT

SecureCRT is not free software. To obtain SecureCRT license please visit https://www.vandyke.com/products/securecrt/

Register Telnet/SSH URL Handler

1. Download securecrt.reg
2. Edit path to SecureCRT if differs from C:\Program Files\VanDyke Software\SecureCRT\SecureCRT.exe
3. Launch securecrt.reg to associate ssh:// and telnet:// to this script