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104 ServerIron ADX Security Guide
53-1002440-03
Translation timeouts
4
ServerIronADX(config)# nat-forward-no-session
Syntax: [no] nat-forward-no-session
Translation timeouts
The NAT translation table contains all the currently active NAT translation entries on the device. An
active entry is one the ServerIron ADX creates for a private address when the client at that address
sends traffic.
NAT performs the following steps to provide an address translation for a source IP address:
• NAT looks in the translation table for an active NAT entry for the translation. If the table
contains an active entry for the session, the ServerIron ADX uses that entry.
• If NAT does not find an active entry in the NAT translation table, NAT creates an entry and
places the entry in the table. The entry remains in the table until the entry times out.
Each NAT entry remains in the translation table until the entry ages out.
After the configuration of a NAT timeout the following occurs:
• Existing entries of the modified protocol remain in the translation table.
• If existing session entries send or receive packets then the timeout value is updated to the new
configured value.
• If existing session entries do not process any traffic they will continue to age out in accordance
with the old timeout value.
• When the timeout (age of the session) expires, forward and reverse sessions in the ServerIron
ADX are deleted with no further actions. If traffic is received on this flow the ServerIron ADX
drops the packets because it will not find sessions related to that particular flow.
Configuring the NAT translation aging timer
Use the ip nat translation command to alter the NAT translation aging timer.
The NAT translation table contains all the currently active NAT translation entries on the device. An
active entry is one that the ServerIron ADX created for a private address when that client at that
address sent traffic to the Internet. NAT performs the following steps to provide an address
translation for a source IP address:
• The feature looks in the NAT translation table for an active NAT entry for the translation. If the
table contains an active entry for the session, the ServerIron ADX uses that entry.
• If NAT does not find an active entry in the NAT translation table, NAT creates an entry and
places the entry in the table. The entry remains in the table until the entry times out.
ServerIronADX(config)# ip nat translation tcp-timeout 1800
Syntax: [no] ip nat translation dns-timeout | finrst-timeout | icmp-timeout | syn-timeout |
tcp-timeout | udp-timeout <secs> maximum
Syntax: [no] ip nat translation max-entries <number-of-entries>
The dns-timeout keyword indicates connections to a Domain Name Server (DNS). The default is
120 seconds.