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Manual Chapter: Working with Listeners
Manual Chapter
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Before you can fully configure the Link Controller system to handle name resolution requests, you must determine how you want to integrate the system into your existing network. Part of this integration includes identifying what network traffic is relevant to the Link Controller system and how you want the system to respond to this traffic. In general, you have two options when handling traffic with the Link Controller system:
The system receives the traffic, processes it locally, and sends the appropriate DNS response back to the querying server. Global Traffic Manager systems with this configuration are considered to be running in node mode.
The system receives the traffic and forwards it to either another part of the network or another DNS server. Global Traffic Manager systems with this configuration are considered to be running in either bridge mode or router mode, depending on where the system is forwarding network traffic.
To control how the Link Controller system handles network traffic, you configure one or more listeners. A listener is a specialized resource that is assigned a specific IP address and uses port 53, the DNS query port. When traffic is sent to that IP address, the listener alerts the system, allowing it to handle the traffic locally or forward the traffic to the appropriate resource.
Tip: If you are familiar with the Local Traffic Manager, it might be helpful to consider a listener as a specialized type of virtual server that is responsible for handling traffic for the Link Controller system.
You control how the Link Controller system responds to network traffic on a per-listener basis. For example, a single Link Controller system can be the authoritative server for one domain, while forwarding other requests to a separate DNS server. Regardless of how many listeners you configure, the system always manages and responds to requests for any wide IPs that you have configured on it.
Often, when you add a Link Controller system, you want the system to respond to at least a subset of your incoming DNS requests. These requests can be directed at wide IPs that you have configured on the Link Controller system, but you are not limited to wide IPs alone. You can also configure the Link Controller system to respond to DNS requests for other network resources that might not be associated with a wide IP.
When a Link Controller system is operating in node mode, you assign it a listener that corresponds to an IP address on the Link Controller system. If the Link Controller system is operating as a standalone unit, this IP address is the self IP address of the Link Controller system. If the Link Controller is part of a redundant system configuration for high availability purposes, this IP address is the floating IP address that belongs to both systems.
1.
On the Main tab of the navigation pane, expand Link Controller and then click Listeners.
The main listeners screen opens.
2.
Click the Create button.
The New Listener screen opens.
3.
In the Destination box, type the IP address on which the Link Controller system listens for network traffic.
In this case, the IP address that you add is either the self IP address of the system, or, in the case of a redundant system configuration, the floating IP address that corresponds to both systems.
4.
From the VLAN Traffic list, select a VLAN setting appropriate for this listener.
Typically, if the Link Controller system is handling traffic on this IP address locally, you would select All VLANs for this option
5.
Click the Finished button to save the new listener.
Another common configuration you can use with the Link Controller system is to integrate it with your existing DNS servers. In this scenario, the Link Controller system handles any traffic related to the wide IPs you assign to it, while sending other DNS requests to another DNS server on your network. When forwarding traffic in this manner, the system is considered to be operating in bridge or router mode, depending on how the traffic was initially sent to the Link Controller system. In this configuration, you assign a listener to the Link Controller system that corresponds to the IP address of the DNS server to which you want to forward to traffic.
Unlike the steps described in Creating a listener for local resolution, you can create more than one listener to forward network traffic. The number of listeners depends on your network configuration and the ultimate destination to which you want to send specific DNS requests.
1.
On the Main tab of the navigation pane, expand Link Controller and then click Listeners.
The main listeners screen opens.
2.
Click the Create button.
The New Listener screen opens.
3.
In the Destination box, type the IP address on which the Link Controller system listens for network traffic.
In this case, the IP address that you add is the IP address of the DNS server that you want to handle the DNS request.
4.
From the VLAN Traffic list, select a VLAN setting appropriate for this listener.
Typically, if the Link Controller system is handling traffic on this IP address locally, you would select All VLANs for this option
5.
Click the Finished button to save the new listener.
In some cases, you might want the Link Controller system to handle any traffic coming into your network, regardless of the destination IP address of the given DNS request. In this configuration, the Link Controller system continues to process and respond to requests for the wide IPs that you configure, but in addition it is responsible for forwarding any other DNS requests to other network resources, such other DNS servers. To accomplish this type of configuration, you assign a wildcard listener to the system. A wildcard listener is the same as a standard listener, except that it contains an asterisk (*) instead of an IP address.
1.
On the Main tab of the navigation pane, expand Link Controller and then click Listeners.
The main listeners screen opens.
2.
Click the Create button.
The New Listener screen opens.
3.
In the Destination box, type an asterisk (*).
4.
From the VLAN Traffic list, select a VLAN setting appropriate for this listener.
5.
Click the Finished button to save the new listener.
After you create a listener, you can access its settings, changing them as needed. Common instances in which you need to modify a listener include adding an additional VLAN, or modifying the IP address of the listener.
1.
On the Main tab of the navigation pane, expand Link Controller and then click Listeners.
The main listeners screen opens.
2.
Click the name of the listener.
The properties screen for that listener appears.
4.
Click the Update button to save your changes to the listener.
1.
On the Main tab of the navigation pane, expand Link Controller and then click Listeners.
The main listeners screen opens.
3.
Click the Delete button.
A confirmation screen appears.
4.
Click the Delete button to delete the listener.
One of the features of a BIG-IP® system is that you can create one or more VLANs and assign specific interfaces to the VLANs of your choice. By default, each BIG-IP system includes at least two VLANs, named internal and external. However, you can create as many VLANs as the needs of your network demands.
When you assign listeners to the Link Controller system, you must take into account any VLANs that you have created. For example, a listener that forwards traffic to another DNS server might only be appropriate for a specific VLAN, while a wildcard listener might be applicable to all VLANs. You can configure a listener to be applicable to all VLANs, enabled only on specific VLANs, or disabled on specific VLANs.
Note: For more information about BIG-IP systems and VLANs, see the TMOS® Management Guide for BIG-IP® Systems.
If the Link Controller system resides on a network segment that does not use VLANs, or if the IP address you assign as a listener is valid for all VLANs for which the system is responsible, you set the VLAN Traffic option to All VLANs.
1.
On the Main tab of the navigation pane, expand Link Controller and then click Listeners.
The main listeners screen opens.
2.
Click the Create button.
The New Listener screen opens.
3.
In the Destination box, type the IP address on which the Link Controller system listens for network traffic.
4.
From the VLAN Traffic list, select All VLANs.
5.
Click Finished.
If the Link Controller system manages traffic for only some of the VLANs available on the network segment, you set the VLAN Traffic option to Enabled on.
1.
On the Main tab of the navigation pane, expand Link Controller and then click Listeners.
The main listeners screen opens.
2.
Click the Create button.
The New Listener screen opens.
3.
In the Destination box, type the IP address on which the Link Controller system listens for network traffic.
4.
From the VLAN Traffic list, select Enabled on.
A new option, VLAN List, appears on the screen.
5.
Select the appropriate VLANs from the Available list and use the buttons provided to move them to the Selected list.
The listener only alerts the Link Controller system about traffic on the VLANs in the Selected list.
6.
Click the Finished button to save your changes.
In instances where the Link Controller system resides on a network segment with several VLANs, and you want to exclude some VLANs from listener, you set the VLAN Traffic option to Disabled on.
1.
On the Main tab of the navigation pane, expand Link Controller and then click Listeners.
The main listeners screen opens.
2.
Click the Create button.
The New Listener screen opens.
3.
From the VLAN Traffic list, select Disabled on.
A new option, VLAN List, appears on the screen.
4.
Select the appropriate VLANs from the Available list and use the buttons provided to move them to the Selected list.
The listener alerts the Link Controller system about traffic on all VLANs except those listed in the Selected list.
5.
Click the Finished button to save your changes.
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