Table 84 Example: Routing Table Entry For A Gateway - ZyXEL Communications ZyWALL USG 100 Series User Manual

Chapter 10 Interface
In the example above, if the ZyWALL 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 ZyWALL 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 wan1. In this case, the ZyWALL creates the
following entry in the routing table.

Table 84 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 computers in the network. This
reduces the amount of manual configuration you have to do and usually uses available IP
addresses more efficiently.
1. At the time of writing, the ZyWALL does not support ingress bandwidth management.
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DESTINATION
200.200.200.100
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ZyWALL USG 100/200 Series User's Guide