Chapter 9 Interfaces
USG20(W)-VPN Series User’s Guide
216
9.10 Interface Technical Reference
Here is more detailed information about interfaces on the USG.
IP Address Assignment
Most interfaces have an IP address and a subnet mask. This information is used to create an entry
in the routing table.
Figure 143
Example: Entry in the Routing Table Derived from Interfaces
For example, if the USG gets a packet with a destination address of 100.100.25.25, it routes the
packet to interface lan1. If the USG gets a packet with a destination address of 200.200.200.200, it
routes the packet to interface wan1.
In most interfaces, you can enter the IP address and subnet mask manually. In PPPoE/PPTP
interfaces, however, the subnet mask is always 255.255.255.255 because it is a point-to-point
interface. For these interfaces, you can only enter the IP address.
In many interfaces, you can also let the IP address and subnet mask be assigned by an external
DHCP server on the network. In this case, the interface is a DHCP client. Virtual interfaces,
however, cannot be DHCP clients. You have to assign the IP address and subnet mask manually.
In general, the IP address and subnet mask of each interface should not overlap, though it is
possible for this to happen with DHCP clients.
In the example above, if the USG gets a packet with a destination address of 5.5.5.5, it might not
find any entries in the routing table. In this case, the packet is dropped. However, if there is a
default router to which the USG should send this packet, you can specify it as a gateway in one of
the interfaces. For example, if there is a default router at 200.200.200.100, you can create a
gateway at 200.200.200.100 on ge2. In this case, the USG creates the following entry in the
routing table.
Table 83
Example: Routing Table Entries for Interfaces
IP ADDRESS(ES)
DESTINATION
100.100.1.1/16
lan1
200.200.200.1/24
wan1
Table 84
Example: Routing Table Entry for a Gateway
IP ADDRESS(ES)
DESTINATION
0.0.0.0/0
200.200.200.100
lan1
wan1
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