ZyXEL Communications ZyWall USG 2000 User Manual page 222

Chapter 10 Interfaces
200.200.200.100 on ge2. In this case, the ZyWALL creates the following entry in
the routing table.
Table 66 Example: Routing Table Entry for a Gateway
IP ADDRESS(ES)
0.0.0.0/0
The gateway is an optional setting for each interface. If there is more than one
gateway, the ZyWALL uses the gateway with the lowest metric, or cost. If two or
more gateways have the same metric, the ZyWALL uses the one that was set up
first (the first entry in the routing table). In PPPoE/PPTP interfaces, the other
computer is the gateway for the interface by default. In this case, you should
specify the metric.
If the interface gets its IP address and subnet mask from a DHCP server, the
DHCP server also specifies the gateway, if any.
Interface Parameters
The ZyWALL restricts the amount of traffic into and out of the ZyWALL through
each interface.
• Egress bandwidth sets the amount of traffic the ZyWALL sends out through the
interface to the network.
• Ingress bandwidth sets the amount of traffic the ZyWALL allows in through the
interface from the network.
If you set the bandwidth restrictions very high, you effectively remove the
restrictions.
The ZyWALL also restricts the size of each data packet. The maximum number of
bytes in each packet is called the maximum transmission unit (MTU). If a packet is
larger than the MTU, the ZyWALL divides it into smaller fragments. Each fragment
is sent separately, and the original packet is re-assembled later. The smaller the
MTU, the more fragments sent, and the more work required to re-assemble
packets correctly. On the other hand, some communication channels, such as
Ethernet over ATM, might not be able to handle large data packets.
DHCP Settings
Dynamic Host Configuration Protocol (DHCP, RFC 2131, RFC 2132) provides a way
to automatically set up and maintain IP addresses, subnet masks, gateways, and
some network information (such as the IP addresses of DNS servers) on
1. At the time of writing, the ZyWALL does not support ingress bandwidth management.
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DESTINATION
200.200.200.10
0
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ZyWALL USG 2000 User's Guide