Now that we have added the license and configured most of the basic features, such as DNS, NTP, and SNMP, it's time to take a closer look at the different modes through which NetScaler can process traffic. The different modes can be found by navigating to System | Settings | Configure Modes.
Here, there are modes that we can configure depending on the following parameters:
How do we want NetScaler to process network traffic such as L2 and L3?
Where is NetScaler placed?
Not all the advanced features are covered here, as some of them are not relevant for every environment. Information about the remaining features can be found in the Citrix article at http://support.citrix.com/article/CTX121149. The different modes here decide how NetScaler should handle different kinds of traffic. So, a quick overview of the different modes is as follows:
Fast Ramp: This mode bypasses the slow-start mechanism of the TCP protocol and allows for a faster increment of TCP windowing, thereby allowing for faster packet transmission. This feature is enabled by default.
Layer 2 mode: This mode allows NetScaler to behave as a switch and should only be used if servers are directly attached to NetScaler, or if it is being used as a transparent bridge, for example, CloudBridge.
Use Source IP: By default, when NetScaler connects to a backend server, it uses one of its own addresses to establish a connection. By enabling the Use Source IP mode, the end client IP address is used to connect to the backend server. This should only be used in deployments where you need direct connections from the clients, or when you have an IDS environment. Make sure that when this feature is enabled, the backend servers must have one of NetScaler's IP addresses to be used as the Gateway IP address.
Client Keep-Alive: This feature is mostly useful when the backend server or service does not support client keep-alive. It allows clients to maintain connectivity to the appliance even if the backend server closes the connection. This eliminates the need to reestablish the connection between the client and the backend server, and will reduce the time needed for a client to reopen the connection. This feature should only be enabled if there are performance issues with a service.
TCP Buffering: This feature allows the adjustment of speed between a high-speed server and a slow client. If a backend server responds too fast for a client, the appliance will buffer the packets and adjust the speed based upon the speed of the client. This allows the backend server to devote the CPU resources to other tasks. This mode should be enabled if there are performance issues or if the TCP window scaling does not work, or shows high-packet loss.
MAC-based Forwarding: This mode allows NetScaler to return packets based upon the MAC address of the received packet. For example, in environments where you have multiple routers, and you need to make sure that the packets are returned through the same path, you need to enable the MAC-based Forwarding mode. If this feature is disabled, the return path is based upon the route lookup. By default, this feature is not enabled.
Edge Configuration: Enable this feature if clients are using the link load-balancing feature.
Use Subnet IP: This feature allows for the use of subnet IP addresses.
Layer 3 mode: When the Layer 3 mode is enabled, the NetScaler appliance performs route table lookups and forwards all packets that are not destined for any NetScaler-owned IP address. This mode is enabled by default, but it should be disabled if not used for security purposes.
Path MTU Discovery: This mode allows network devices to share information to determine the largest MTU size that can be allowed on a network, which reduces the amount of IP packet fragmentation. This mode is enabled by default.
Static Route Advertisement: This mode allows for the advertisement of static routes when using dynamic routing protocols.
Direct Route Advertisement: This mode allows for the advertisement of direct routes when using dynamic routing protocols.
Intranet Route Advertisement: This mode allows for the advertisement of intranet routes when using dynamic routing protocols.
IPv6 Static Route Advertisement: This mode allows for the advertisement of IPv6 static routes when using dynamic routing protocols.
IPv6 Direct Route Advertisement: This mode allows for the advertisement of IPv6 direct routes when using dynamic routing protocols.
Bridge BDPUs: This mode is used for the Spanning Tree Protocol, allowing NetScaler to participate or not participate in the STP state.
Media Classification: This mode is used to classify media content that is passed through NetScaler.