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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | NOTES | SEE ALSO | COLOPHON |
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NAT action in tc(8) Linux NAT action in tc(8)
nat - stateless native address translation action
tc ... action nat DIRECTION OLD NEW
DIRECTION := { ingress | egress }
OLD := IPV4_ADDR_SPEC
NEW := IPV4_ADDR_SPEC
IPV4_ADDR_SPEC := { default | any | all |
in_addr[/{prefix|netmask}]
The nat action allows one to perform NAT without the overhead of
conntrack, which is desirable if the number of flows or addresses
to perform NAT on is large. This action is best used in
combination with the u32 filter to allow for efficient lookups of
a large number of stateless NAT rules in constant time.
ingress
Translate destination addresses, i.e. perform DNAT.
egress Translate source addresses, i.e. perform SNAT.
OLD Specifies addresses which should be translated.
NEW Specifies addresses which OLD should be translated into.
The accepted address format in OLD and NEW is quite flexible. It
may either consist of one of the keywords default, any or all,
representing the all-zero IP address or a combination of IP
address and netmask or prefix length separated by a slash (/)
sign. In any case, the mask (or prefix length) value of OLD is
used for NEW as well so that a one-to-one mapping of addresses is
assured.
Address translation is done using a combination of binary
operations. First, the original (source or destination) address
is matched against the value of OLD. If the original address
fits, the new address is created by taking the leading bits from
NEW (defined by the netmask of OLD) and taking the remaining bits
from the original address.
There is rudimental support for upper layer protocols, namely
TCP, UDP and ICMP. While for the first two only checksum
recalculation is performed, the action also takes care of
embedded IP headers in ICMP packets by translating the respective
address therein, too.
tc(8)
This page is part of the iproute2 (utilities for controlling
TCP/IP networking and traffic) project. Information about the
project can be found at
⟨http://www.linuxfoundation.org/collaborate/workgroups/networking/iproute2⟩.
If you have a bug report for this manual page, send it to
[email protected], [email protected]. This page was
obtained from the project's upstream Git repository
⟨https://git.kernel.org/pub/scm/network/iproute2/iproute2.git⟩ on
2024-06-14. (At that time, the date of the most recent commit
that was found in the repository was 2024-06-11.) If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better or more up-to-date source for
the page, or you have corrections or improvements to the
information in this COLOPHON (which is not part of the original
manual page), send a mail to [email protected]
iproute2 12 Jan 2015 NAT action in tc(8)
Pages that refer to this page: tc-actions(8)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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