Brocade Communications Systems ServerIron ADX 12.4.00a - Manual (Page 133)

ServerIron ADX Security Guide 119
53-1002440-03
Configuring Syn-Proxy
5
The <mss-value> variable specifies MSS value for all SYN-ACK packets generated by the ServerIron
ADX for this virtual server 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.
Setting the MSS value at the virtual port level
To set the MSS value for a specific virtual port on a ServerIron ADX, use the following command:
ServerIronADX(config)# server virtual-name-or-ip v1
ServerIronADX(config-vs-v1)# port http tcp-mss 128
Syntax: [no] port tcp-mss <mss-value>
The <mss-value> variable specifies MSS value for all SYN-ACK packets generated by the ServerIron
ADX for the port specified by the variable 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.
Setting the MSS value for pass-through traffic to a specified destination IP
address
To set the MSS value for ServerIron ADX pass-through traffic to a specified destination IP address,
use the following commands.
ServerIronADX(config)# tcp-mss 128 destination-ip 207.95.55.1
For IPv4
Syntax: [no] tcp-mss <mss-value> destination-ip <ip-address>
For IPv6
Syntax: [no] tcp-mss <mss-value> destination-ipv6 <ipv6-address>
The <mss-value> variable specifies MSS value for all SYN-ACK packets that are ServerIron ADX
pass-through traffic to a destination IP address specified by the <ip-address> variable. This value
can be from 64 to 9216. Make sure that the IP MTU of the interfaces is always greater than the
MSS value.
The <ip-address> or <ipv6-address> cannot be a Virtual server IP address.
Negotiated MSS value set
Once tcp-mss is configured with the minimum value, the ServerIron ADX will generate a negotiated
MSS value in SYN-ACK base on the configured minimum MSS value. This MSS value will be the
final MSS value after negotiation.
For example, if a user configures tcp-mss 1200, which is in the range of 1024 and 1440, a
ServerIron ADX will use the lower 1024 as the negotiated MSS value in the SYN-ACK.
TABLE 9 MSS values for IPv4, IPv6 and IPv4 jumbo
MSS value
IPv4 64, 256, 536, 966, 1024, 1440, 1452, 1460