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Cisco ASA 5500 Series Configuration Guide using ASDM
Chapter57 Configuring Connection Settings
Configuring Connection Settings
Step8 Click OK.
Configuring Connection Settings
To set connection settings, perform the following steps.
Guidelines and Limitations
Depending on the number of CPU cores on your ASA model, the maximum concurrent and embryonic
connections may exceed the configured numbers due to the way each core manages connections. In the
worst case scenario, the ASA allows up to n-1 extra connections and embryonic connections, where n is
the number of cores. For example, if your model has 4 cores, if you configure 6 concurrent connections
and 4 embryonic connections, you could have an additional 3 of each type. To determine the number of
cores for your model, enter the show cpu core command.
Detailed Steps
Step1 Configure a service policy on the Configuration > Firewall > Service Policy Rules pane according to
Chapter 36, “Configuring a Service Policy.”
You can configure connection limits as part of a new service policy rule, or you can edit an existing
service policy.
Step2 On the Rule Actions dialog box, click the Connection Settings tab.
Step3 To set maximum connections, configure the following values in the Maximum Connections area:
•TCP & UDP Connections—Specifies the maximum number of simultaneous TCP and UDP
connections for all clients in the traffic class, up to 65,536. The default is 0 for both protocols, which
means the maximum possible connections are allowed.
•Embryonic Connections—Specifies the maximum number of embryonic connections per host up to
65,536. An embryonic connection is a connection request that has not finished the necessary
handshake between source and destination. This limit enables the TCP Intercept feature. The default
is 0, which means the maximum embryonic connections. TCP Intercept protects inside systems from
a DoS attack perpetrated by flooding an interface with TCP SYN packets. When the embryonic limit
has been surpassed, the TCP intercept feature intercepts TCP SYN packets from clients to servers
on a higher security level. SYN cookies are used during the validation process and help to minimize
the amount of valid traffic being dropped. Thus, connection attempts from unreachable hosts will
never reach the server.
•Per Client Connections—Specifies the maximum number of simultaneous TCP and UDP
connections for each client. When a new connection is attempted by a client that already has opened
the maximum per-client number of connections, the ASA rejects the connection and drops the
packet.
•Per Client Embryonic Connections—Specifies the maximum number of simultaneous TCP
embryonic connections for each client. When a new TCP connection is requested by a client that
already has the maximum per-client number of embryonic connections open through the ASA, the
ASA proxies the request to the TCP Intercept feature, which prevents the connection.
Step4 To configure connection timeouts, configure the following values in the TCP Timeout area: