Network Address Translation (NAT) involves translating the
source and or destination IP addresses of packets as they
traverse from one IP domain to another. NAT is usually
performed on packets that are routed, and there is a MIB
already defined for that, but the application addressed
here is for performing NAT for Layer 2 switched packets.
This MIB module defines objects and tables for Network
Address Translation (NAT) performed at layer 2. This
application is planned currently for Industrial Ethernet
switches, but this could be used for other applications.
This platform implements NAT using an FPGA which connects
to uplinks, so NAT is only applicable for packets
coming in from uplinks, and going out of uplinks.
There are 3 main logical modules that are referred in this MIB.
Global parameters : These provide statistics for the
entire platform.
L2NAT Instance Table : This table contains multiple
Layer 2 NAT instances. A Layer 2 NAT instance referred 
throughout this MIB is an entity that is defined with respect 
to the Layer 2 NAT feature, and is different from the concept 
of instance as used in SNMP. Each Layer 2 NAT instance has a 
unique number.
Each Layer 2 NAT instance consists of packets that are to be 
permitted or denied, as well as packets that are supposed to be 
fixed up. Fixup is a NAT concept which applies to certain 
applications which embed IP addresses in the payload. For these 
applications to work across NAT, the embedded IP addresses need 
to be translated along with the header IP addresses.
Each Layer 2 NAT instance also contains a list of source and/or 
destination IP address translations
An instance only becomes effective on traffic after being 
applied to an interface vlan combination. This table actually 
consists of these 2 MIB tables in order for indexing to work, 
cl2natInstanceTable and cl2natInstanceIpTable
L2NAT Interface Config Table : This table contains multiple
entries, where each entry contains configuration
for the instance applied to an interface vlan combination.
This table actually consists of these 2 MIB tables in order for 
indexing to work cl2natInterfaceConfigTable and 
cl2natInterfaceIpConfigTable.
L2NAT Interface Statistics Table : This table contains multiple
entries, where each entry contains stats for the instance 
applied to an interface vlan combination.
This table actually consists of these 2 MIB tables in order for 
indexing to work , cl2natInterfaceStatisticsTable and 
cl2natInterfaceIpStatisticsTable.