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   SAME
       Similar to SNAT/DNAT depending on chain: it takes a range of addresses (‘--to 1.2.3.4-1.2.3.7’) and gives a client the  same  source-/destination-
       address for each connection.

       N.B.: The DNAT target’s --persistent option replaced the SAME target.

       --to ipaddr[-ipaddr]
              Addresses to map source to. May be specified more than once for multiple ranges.

       --nodst
              Don’t use the destination-ip in the calculations when selecting the new source-ip

       --random
              Port mapping will be forcibly randomized to avoid attacks based on port prediction (kernel >= 2.6.21).
(...)
   SNAT
       This target is only valid in the nat table, in the POSTROUTING chain.  It specifies that the source address of the packet should be modified  (and
       all future packets in this connection will also be mangled), and rules should cease being examined.  It takes one type of option:

       --to-source ipaddr[-ipaddr][:port[-port]]
              which  can specify a single new source IP address, an inclusive range of IP addresses, and optionally, a port range (which is only valid if
              the rule also specifies -p tcp or -p udp).  If no port range is specified, then source ports below 512 will be mapped to other ports  below
              512: those between 512 and 1023 inclusive will be mapped to ports below 1024, and other ports will be mapped to 1024 or above. Where possi‐
              ble, no port alteration will

              In Kernels up to 2.6.10, you can add several --to-source options. For those kernels, if you specify more than one  source  address,  either
              via  an  address  range  or  multiple  --to-source  options,  a  simple  round-robin (one after another in cycle) takes place between these
              addresses.  Later Kernels (>= 2.6.11-rc1) don’t have the ability to NAT to multiple ranges anymore.

       --random
              If option --random is used then port mapping will be randomized (kernel >= 2.6.21).

       --persistent
              Gives a client the same source-/destination-address for each connection.  This supersedes the SAME target. Support for persistent  mappings
              is available from 2.6.29-rc2.

iptables -t nat -A POSTROUTING -s 10.1.230.0/24 -j SNAT 1.2.3.4-1.2.3.5 --persistent
jest równoważne
iptables -t nat -A POSTROUTING -s 10.1.230.0/24 -j SAME 1.2.3.4-1.2.3.5

#uname -r
2.6.30.9-imq
(customized)

# cat /boot/config-$(uname -r) | grep -i sane
CONFIG_NF_CONNTRACK_SANE=m

# iptables -t nat -A POSTROUTING -s 10.1.230.0/24 -j SAME
iptables v1.4.5: SAME needs --to
Try `iptables -h' or 'iptables --help' for more information.