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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
118 ServerIron ADX Security Guide
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Configuring Syn-Proxy
5
• Virtual server lever – configures the TCP MSS value for all virtual ports under a specified virtual
server
• Virtual port level – configures the TCP MSS value for a specified virtual port
• Destination IP – configures the TCP MSS value for pass-through traffic to a specified
destination IP address
NOTE
tcp-mss will work when syn-proxy is enabled. If syn-proxy is turned off, tcp-mss will not take effect.
If the configured mininum MSS is larger than the client's actual MSS value, the ServerIron ADX will
use the client's MSS value in SYN-ACK.
Hierarchy of operation
When multiple levels of the minimum MSS value are configured, the MSS value used by the
ServerIron ADX is determined by the following hierarchy.
1. Virtual Port Level – Values configured at this level take precedence over any other MSS setting
on the ServerIron ADX.
2. Virtual Server level – Only values configured at the Virtual Port level take precedence over MSS
values configured at this level.
3. Global level – Values configured at this level take effect over all SYN-ACK packets generated by
a ServerIron ADX unless the MSS value is configured at one of the levels previous described in
1, 2 or 3.
Setting the MSS value at the global level
To globally set the MSS value for all SYN-ACK packets generated by a ServerIron ADX, use the
following command:
ServerIronADX(config)# tcp-mss 128
Syntax: [no] tcp-mss <mss-value>
The <mss-value> variable specifies MSS value for all SYN-ACK packets generated by the ServerIron
ADX regardless of the client’s MSS value. This value can be from 64 to 9216. Make sure that the IP
MTU of the interfaces is always greater than the MSS value.
NOTE
When tcp-mss is configured at the global level, the same value will work for both IPv4 traffic and IPv6
traffic.
Setting the MSS value at the virtual server level
To set the MSS value for all of the ports under a virtual server on a ServerIron ADX, use the
following command:
ServerIronADX(config)# server virtual-name-or-ip v1
ServerIronADX(config-vs-v1)# tcp-mss 128
Syntax: [no] tcp-mss <mss-value>