Vertiv Avocent - Page 86

Figure 6.8 Firewall Flow
ITEM DESCRIPTION
1 Outside.
2 Inside.
3 Input filter on an inside interface.
4 Input filter on an outside interface.
5 Output filter on an inside interface.
6 Output filter on an outside interface.
Table 6.5 Firewall Flow Table Descriptions
Firewall and NATflow
Traffic flowing through the appliance which is expected to be both translated and filtered will require both NATand firewall
rules designed to match the traffic patterns appropriately. Translation happens before filtering when traffic is entering the
appliance and filtering happens before translation when traffic is exiting the appliance.
For example, if input traffic passes through an incoming NATrule, which has translated the destination address, then the
only way for the filter rule to match a destination address is to have the filter rule match the pattern of the translated
destination address and not the original destination address of the traffic. This is because the address was translated before
it could be filtered.
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