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Whenever NAT rules are changed or added, the connection tracking table should be cleared otherwise NAT rules may seem to be not functioning correctly until connection entry expires. |
Types of NAT:
- source NAT or srcnat. This type of NAT is performed on packets that are originated from a natted network. A NAT router replaces the private source address of an IP packet with a new public IP address as it travels through the router. A reverse operation is applied to the reply packets traveling in the other direction.
- destination NAT or dstnat. This type of NAT is performed on packets that are destined for the natted network. It is most commonly used to make hosts on a private network to be accessible from the Internet. A NAT router performing dstnat replaces the destination IP address of an IP packet as it travels through the router towards a private network.
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| Tip |
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Though Source NAT and masquerading perform the same fundamental function: mapping one address space into another one, the details differ slightly. Most noticeably, masquerading chooses the source IP address for the outbound packet from the IP bound to the interface through which the packet will exit. |
Hairpin NAT
Hairpin network address translation (NAT Loopback) is where the device on the LAN is able to access another machine on the LAN via the public IP address of the gateway router.
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