# Configure server availability monitoring

There are different methods for monitoring whether a server or a service running on a server is available.

##

For more details about the product and how to configure features, click Help or press F1.

## Steps

1. Select Configuration, then browse to SD-WAN.
2. Browse to Traffic Handlers.
3. Right-click a Server Pool element, then select Properties.
4. In the Frequency Check field on the Monitoring tab, define how often you want the availability to be checked.
5. From the Method drop-down list, select the method for monitoring the availability of the servers in the Server Pool.
6. (TCP or HTTP methods) Specify the additional options.

   The text in the Request field is sent by the firewall in the first packet after the TCP handshake. The text in the Response field is checked against the first data packet received from the server after the TCP handshake.

   Tip: The response is evaluated using a `begins with` pattern. It is not necessary to enter the complete text of the response.

   When using TCP, if the Request and Response fields are left empty, the Firewall only checks that a connection can be established.

   For example, to check for the HTTPS service, enter 443 as the port number, but leave the Request and Response fields empty. In this case, the firewall only checks that a connection to port 443 can be established.
7. Click OK.

## Server Pool Properties dialog box

Use this dialog box to define Server Pools.

Option | Definition
--- | ---
General tab
Name | The name of the element.
Category (Optional) | Includes the element in predefined categories. Click Select to select a category.
Comment (Optional) | A comment for your own reference.

Option | Definition
--- | ---
External Addresses section
NetLink | Specifies the NetLink you want to use.
IP Address | Specifies the external destination IP address for the Server Pool.
Status | Shows the NetLink status: Enabled or Disabled. Enabled NetLinks are used in the Server Pool.
Proxy ARP/Neighbor Discovery | When enabled, automatically generates a proxy ARP or neighbor discovery entry for the external IP address in the selected network.
Add | Opens the External Address dialog box.
Edit | Opens the External Address dialog box and allows you to change the settings for the selected NetLink.
Remove | Removes the selected external address.
Enable Dynamic DNS Updates | Enables Dynamic DNS Updates from the Server Pool to the DNS Server.
DNS Server | Specifies the External DNS Server element to which the DDNS updates are sent. Note: Only IPv4 addresses are supported for DNS servers for DDNS updates. The External DNS Server element must have an IPv4 address.
FQDN | Specifies the fully qualified domain name (FQDN) for the Server Pool service (for example, “www.example.com”).

Option | Definition
--- | ---
Server Pool Members section
Element | Shows the names of the elements selected as pool members.
IP Address | Shows the IP addresses of the elements selected as pool members.
Add | Adds a row to the table.
Remove | Removes the selected row.
Up | Moves the selected row up.
Down | Moves the selected row down.
Allocate Traffic to Servers by | Defines how likely it is that traffic is redirected to a particular server. Usually it is best to select the least granular option that still produces an acceptable distribution of traffic. The options are (from least granular to most granular): Not Defined — Not Defined has the same effect as the Source Network option. Source Network — Directs traffic coming from the same C-class network to the same server. This option is a good choice when connections come from many different networks. Host — Directs traffic coming from the same IP address to the same server. This option is a good choice when a large portion of connections come from different hosts in the same C-class network. Connection — Makes a new traffic management decision for each new connection. This choice might be necessary if a large portion of connections uses just one IP address. Order — Allocates traffic based on the order of the elements on the list.

Option | Definition
--- | ---
Monitoring tab
Frequency Check | Specifies how often you want the availability to be checked.
Method | Specifies the method for monitoring the availability of the servers in the Server Pool. Ping — Uses ICMP echo request (ping) messages to monitor the availability of the servers. Agent — Uses the Server Pool Monitoring Agent feature. Before enabling this method, make sure that you have installed and configured the Monitoring Agents on all servers. TCP — Checks that a specific TCP service is available. HTTP — Checks that the HTTP service is available.

Option | Definition
--- | ---
When Method is Agent
Port | Defines the port number.

Option | Definition
--- | ---
When Method is TCP
Port | Defines the port number.
Request (Optional) | Specifies the string of ASCII text that the firewall sends.
Response (Optional) | Specifies the string of ASCII text that you expect to receive.

Option | Definition
--- | ---
When Method is HTTP
Port | Defines the port number.
Path | Specifies the path to the webpage.
Host Header (Optional) | Specifies the host name of the web server.
Response (Optional) | Specifies the string of ASCII text that you expect to receive.