There could be various reasons why you may experience network connectivity issues with Skytap VMs. Although Skytap environments by default have access to the public Internet, inbound access is blocked and can be controlled by configuring a sharing portal or assigning a public IP or published service. By default, each environment is isolated from other environments. Inter-Configuration Network Routing (ICNR) connects the networks in multiple Skytap environments, which allows VMs on those networks to communicate with one another. Additionally, multiple networks within an environment are isolated from each other and you need to manually enable routing between networks if you wish to have networking between them.
This KB documents the most common network connectivity issues seen within Skytap and provides suggestions and recommendations that may help to troubleshoot and resolve these issues.
Unable to connect from one Skytap VM to another in the same environment
- Check network adapter settings and verify that the IP address, subnet mask, default gateway and DHCP server are correct and that they match the Skytap settings for an automatic network. In an automatic network, the DHCP and DNS server IP address is the same as the gateway address.
If using a manual network, ensure that the guest OS has the correct IP address and subnet configured and that your DNS server is up and running and serving requests.
Windows: Run ipconfig /all
Linux: Run ifconfig -a/ip a
AIX: ifconfig -a
Display resolver configuration:
IBMi: CFGTCP-> Option 1 "Work with TCP/IP interfaces"
If the VM is connected to an automatic network and the VM is not getting a valid IP address but an APIPA address (e.g. 169.254.xxx.xxx), try disabling the network interface and re-enabling:
Windows: Run ncpa.cpl Right-click the adapter, disable and then re-enable
Linux/AIX:
Using ifconfig - If your interface is eth0, run sudo ifconfig eth0 downto disable and sudo ifconfig eth0 upto enable
Using ip - Run sudo ip link set eth0 downto disable and sudo ip link set eth0 upto enable
Make sure to replace "eth0" with the name of the network interface you want to disable or enable.
IBMi: Run CFGTCP -> Option 1 "Work with TCP/IP interfaces" -> Option 5 "Display" and ensure the "Interface Status" is Active. Note the Line Description (e.g ETHLINE) and run WRKHDWRSC TYPE (*CMN) Select Option 5 "Work with configuration descriptions" on the Ethernet Port Resource and then option 8 "Work with configuration status" on the Line Description. Vary off (Option 2) the Line description and then Vary it back on (Option 1)
- Disconnect and re-connect the network adapter in the Skytap UI:
Click on the gear icon for the VM and click on Network Adapters
Click on Disconnect:
Then click on Connect:
- Ensure the VMs can ping their gateway address. To determine the gateway address, click on the Network settings for the environment in the Skytap UI and the gateway address(es) will be displayed: e.g.
- If the VMs are connected to different networks in the same environment and you're unable to connect from one network to another, you need to ensure that routing has been enabled between these networks via the network setting:
"Allow all traffic between networks in this environment"
If this setting is not enabled:
First suspend or shutdown the VMs in the environment.
Then navigate to the Network Settings page.
Click the checkbox next to Allow all traffic between networks in this environment and restart the VMs.
Unable to ping to/from a Skytap VM
- If you are unable to ping another VM, check to see if any firewall is enabled and configured in the Operating System that may be blocking ICMP requests.
For Windows, you can either open up the firewall and check the inbound/outbound rules manually or you can run netsh advfirewall firewall show rule name=allto check for existing rules:
For Linux, you can check current firewall rules by running sudo iptables -L or sudo firewall-cmd --zone=zone_name --list-all
For AIX, you can check for any existing firewall rules by running /usr/sbin/lsfilt -v 4 –O
Unable to connect from one Skytap VM to another in a different environment
- Inter-Configuration Network Routing (ICNR) lets you connect multiple environments together.
Review the following instructions on how to connect different environments using (ICNR):
https://help.skytap.com/connecting-multiple-environments.html
- Determine if it's only a specific VM in the remote environment that cannot be connected to or if all VM's are affected. If it's only a specific VM that is affected, run through the previous troubleshooting steps listed above. If none of the VMs in the remote network can be connected to, try to disconnect and reconnect the ICNR connection:
NOTE! If you have NAT configured, this operation will cause NAT IP mapping to change!
- If it's possible, suspend ALL VMs in the environment, wait 5 minutes, and then run the VMs. This operation will result in a deployment of a new gateway router for the environment. This operation may need to be done on both sides of the ICNR
Unable to connect to a service or application port on a Skytap VM via published service or public IP
Check to see if the connection is being made to the actual published service:
- Check and confirm that the guest OS is not blocking connections via a firewall. Even if you add a published service to a VM, you may not be able to connect to the VM unless you change the firewall rules to permit access to the IP address and port assigned to the VM. If using a published service, ensure that you are connecting to the correct published service port and that it is being directed to the correct service/application port:
- Confirm that the service/application is running (using commands ps -ef, netstat) and that it is listening on the correct port:
The following examples show that the SSH service is running and listening on port 22
AIX:
Linux:
IBMi: NETSTAT *CNN
If the service/application is not running even after restarting it, check the Operating System logs to see if the reason can be determined. If the service/application is configured to restart automatically after a restart, try restarting the VM.
- Run telnet to connect to the specific published service port to check connectivity:
Example successful connections will show results similar to the following:
If the service is not running, or not listening on the correct port, or if networking is not correctly configured on the host, running telnet to the port will either hang or report an error similar to the following:
In these instances, check the configuration of the application/service in the guest OS as well as any appropriate logging to determine the cause.
Reference links
- Port blocked by firewall: https://help.skytap.com/port-blocked-by-firewall-rule.html
- Connecting multiple environments: https://help.skytap.com/connecting-multiple-environments.html
- Troubleshooting public IP addresses: https://help.skytap.com/troubleshooting-public-ip-addresses.html
- Accessing VMs with published services: https://help.skytap.com/accessing-vms-with-published-services.html
- Routing between networks in the same environment: https://help.skytap.com/routing-between-networks-in-the-same-environment.html
- Controlling public Internet access to VMs: https://help.skytap.com/controlling-public-internet-access-to-vms.html
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