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Table Of Contents
- Contents
- About This Document
- Network Security
- TCP SYN attacks
- IP TCP syn-proxy
- Granular application of syn-proxy feature
- Syn-def
- No response to non-SYN first packet of a TCP flow
- Prioritizing management traffic
- Peak BP utilization with TRAP
- Transaction Rate Limit (TRL)
- Understanding transaction rate limit
- Configuring transaction rate limit
- Configuring the maximum number of rules
- Saving a TRL configuration
- Transaction rate limit command reference
- Global TRL
- TRL plus security ACL-ID
- security acl-id
- Transaction rate limit hold-down value
- Displaying TRL rules statistics
- Displaying TRL rules in a policy
- Displaying IP address with held down traffic
- Refusing new connections from a specified IP address
- HTTP TRL
- Overview of HTTP TRL
- Configuring HTTP TRL
- Displaying HTTP TRL
- Display all HTTP TRL policies
- Display HTTP TRL policy from index
- Display HTTP TRL policy client
- Display HTTP TRL policy starting from index
- Display HTTP TRL policy matching a regular expression
- Display HTTP TRL policy client index (MP)
- Display HTTP TRL policy client index (BP)
- Display HTTP TRL policy for all client entries (BP)
- Downloading an HTTP TRL policy through TFTP
- HTTP TRL policy commands
- Logging for DoS Attacks
- Maximum connections
- clear statistics dos-attack
- Maximum concurrent connection limit per client
- Firewall load balancing enhancements
- Syn-cookie threshhold trap
- Service port attack protection in hardware
- Traffic segmentation
- DNS attack protection
- Access Control List
- How ServerIron processes ACLs
- Default ACL action
- Types of IP ACLs
- ACL IDs and entries
- ACL entries and the Layer 4 CAM
- Configuring numbered and named ACLs
- Modifying ACLs
- Displaying a list of ACL entries
- Applying an ACLs to interfaces
- ACL logging
- Dropping all fragments that exactly match a flow-based ACL
- Enabling ACL filtering of fragmented packets
- Enabling hardware filtering for packets denied by flow-based ACLs
- Enabling strict TCP or UDP mode for flow-based ACLs
- ACLs and ICMP
- Using ACLs and NAT on the same interface (flow-based ACLs)
- Displaying ACL bindings
- Troubleshooting rule-based ACLs
- IPv6 Access Control Lists
- Network Address Translation
- Syn-Proxy and DoS Protection
- Understanding Syn-Proxy
- Configuring Syn-Proxy
- DDoS protection
- Configuring a security filter
- Configuring a Generic Rule
- Configuring a rule for common attack types
- Configuring a rule for ip-option attack types
- Configuring a rule for icmp-type options
- Configuring a rule for IPv6 ICMP types
- Configuring a rule for IPv6 ext header types
- Binding the filter to an interface
- Clearing DOS attack statistics
- Clearing all DDOS Filter & Attack Counters
- Logging for DoS attacks
- Displaying security filter statistics
- Address-sweep and port-scan logging
- Secure Socket Layer (SSL) Acceleration
- SSL overview
- SSL acceleration on the ServerIron ADX
- Configuring SSL on a ServerIron ADX
- Basic SSL profile configuration
- Advanced SSL profile configuration
- Configuring Real and Virtual Servers for SSL Termination and Proxy Mode
- Configuration Examples for SSL Termination and Proxy Modes
- SSL debug and troubleshooting commands
- Displaying socket information
ServerIron ADX Security Guide 121
53-1002440-03
Configuring Syn-Proxy
5
The on-threshold-value variable is used with the on-threshold parameter and specifies the
number of TCP SYN packets received per-second. When this value is exceeded for an interval
time defined by the server syn-attack-detection-interval command, Syn Proxy is enabled on the
ServerIron ADX. This value should be set to a much higher value than the normal TCP SYN
packet arrival rate.
The off-threshold parameter is used to define the rate of syns per-second (specified by the
<off-threshold-value> variable) at which the Syn-proxy feature is disabled (after being previously
enabled) on the ServerIron ADX.
The off-threshold-value variable is used with the off-threshold parameter and specifies the
number of TCP SYN packets received per-second. When the rate received drops below this
value, the ServerIron ADX waits ten seconds and then disables Syn-proxy. The
<off-threshold-value >variable must be less than the <on-threshold-value> variable.
Setting the interval time for counting TCP SYN packets
The rate at which Syn-proxy is enabled and disabled is determined by the thresholds set in the ip
tcp syn-proxy on-threshold <on-threshold-value> off-threshold <off-threshold-value> command
over the time period specified in the server syn-attack-detection-interval command. This interval is
configured on the ServerIron ADX as shown in the following.
ServerIronADX(config)# server syn-attack-detection-interval 10
Syntax: server syn-attack-detection-interval <detection-interval-value>
The <detection-interval-value> variable defines the interval that is used to define the time for
counting TCP SYN packets. The range of settings for this interval is 1 to 10 with each level
representing 100 ms. Consequently, the interval can be from 100 ms to 1 second. If the interval
value is smaller, the reaction time for enabling Syn-proxy is shorter, and the measurement of the
TCP syn-packet arrival rate is less accurate. If the interval value is larger, the reaction time for
enabling syn-proxy is longer, and the measurement of TCP syn-packet arrival rate is more accurate.
The default interval value is 3 (in effect 300ms).
Displaying Syn-Proxy Commands
This section contains the following sections:
• “Displaying TCP Attack Information” on page 122
• “Displaying Server Traffic information” on page 122
• “Displaying SYN Cookie Information” on page 123