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Getting Started with Citrix NetScaler
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Deploy a Citrix NetScaler VPX instance
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Install a NetScaler VPX instance on Microsoft Hyper-V servers
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Install a NetScaler VPX instance on Linux-KVM platform
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Prerequisites for Installing NetScaler VPX Virtual Appliances on Linux-KVM Platform
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Provisioning the NetScaler Virtual Appliance by using OpenStack
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Provisioning the NetScaler Virtual Appliance by using the Virtual Machine Manager
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Configuring NetScaler Virtual Appliances to Use SR-IOV Network Interface
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Configuring NetScaler Virtual Appliances to use PCI Passthrough Network Interface
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Provisioning the NetScaler Virtual Appliance by using the virsh Program
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Provisioning the NetScaler Virtual Appliance with SR-IOV, on OpenStack
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Configuring a NetScaler VPX Instance on KVM to Use OVS DPDK-Based Host Interfaces
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Upgrade and downgrade a NetScaler appliance
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Persistence and persistent connections
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Advanced load balancing settings
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Gradually stepping up the load on a new service with virtual server–level slow start
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Protect applications on protected servers against traffic surges
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Use source IP address of the client when connecting to the server
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Set a limit on number of requests per connection to the server
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Configure automatic state transition based on percentage health of bound services
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Use case 2: Configure rule based persistence based on a name-value pair in a TCP byte stream
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Use case 3: Configure load balancing in direct server return mode
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Use case 6: Configure load balancing in DSR mode for IPv6 networks by using the TOS field
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Use case 7: Configure load balancing in DSR mode by using IP Over IP
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Use case 10: Load balancing of intrusion detection system servers
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Use case 11: Isolating network traffic using listen policies
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Use case 14: ShareFile wizard for load balancing Citrix ShareFile
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Configuring a CloudBridge Connector Tunnel between two Datacenters
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Configuring CloudBridge Connector between Datacenter and AWS Cloud
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Configuring a CloudBridge Connector Tunnel Between a Datacenter and Azure Cloud
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Configuring CloudBridge Connector Tunnel between Datacenter and SoftLayer Enterprise Cloud
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Configuring a CloudBridge Connector Tunnel Between a NetScaler Appliance and Cisco IOS Device
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CloudBridge Connector Tunnel Diagnostics and Troubleshooting
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Layer 3-4 SYN Denial-of-Service protection
Any NetScaler appliance with system software version 8.1 or later automatically provides protection against SYN DoS attacks.
To mount such an attack, a hacker initiates a large number of TCP connections but does not respond to the SYN-ACK messages sent by the victimized server. The source IP addresses in the SYN messages received by the server are typically spoofed. Because new SYN messages arrive before the half-open connections initiated by previous SYN messages time out, the number of such connections increases until the server no longer has enough memory available to accept new connections. In extreme cases, the system memory stack can overflow.
A NetScaler appliance defends against SYN flood attacks by using SYN cookies instead of maintaining half-open connections on the system memory stack. The appliance sends a cookie to each client that requests a TCP connection, but it does not maintain the states of half-open connections. Instead, the appliance allocates system memory for a connection only upon receiving the final ACK packet, or, for HTTP traffic, upon receiving an HTTP request. This prevents SYN attacks and allows normal TCP communications with legitimate clients to continue uninterrupted.
SYN DoS protection on the NetScaler appliance ensures the following:
- The memory of the NetScaler is not wasted on false SYN packets. Instead, memory is used to serve legitimate clients.
- Normal TCP communications with legitimate clients continue uninterrupted, even when the Web site is under SYN flood attack.
In addition, because the NetScaler appliance allocates memory for HTTP connection state only after it receives an HTTP request, it protects Web sites from idle connection attacks.
SYN DoS protection on your NetScaler appliance requires no external configuration. It is enabled by default.
Disable SYN Cookies
SYN cookies are enabled by default on a NetScaler appliance to prevent SYN attacks. If your deployment requires you to disable SYN cookies, for example, for server-initiated data connections or in cases where a connection is not established because the first packet is dropped or reordered, use one of the following methods to disable SYN cookies.
Disable SYN cookies by using the CLI
At the command prompt, type:
set nstcpprofile nstcp_default_profile -synCookie DISABLED
**Arguments**
synCookie
Enable or disable the SYNCOOKIE mechanism for TCP handshake with clients. Disabling SYNCOOKIE prevents SYN attack protection on the NetScaler appliance.
Possible values: ENABLED, DISABLED
Default: ENABLED
Disable SYN cookies by using the GUI
- Navigate to System > Profiles > TCP Profiles.
- Select a profile and click Edit.
- Clear the TCP SYN Cookie check box.
- Click OK.
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