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Changing MTU size to improve network performance
To improve the performance of your internet connection, you can adjust the maximum transmission unit
(MTU) of the packets that the DFL-1000 transmits from its external interface. Ideally, you want this MTU
to be the same as the smallest MTU of all the networks between your machine and the Internet. If your
packets are larger, they get broken up or fragmented, which slows down transmission speeds.
Trial and error is the only sure way of finding the optimal MTU, but there are some guidelines that can
help. For example, the MTU of many PPP connections is 576, so if you connect to the Internet via PPP or
PPPoE, you might want to set the MTU of the DFL-1000 to 576. DSL modems may also have small MTU
sizes. Most ethernet networks have an MTU of 1500
If you connect to your ISP using DHCP to obtain an IP address for the external interface, you cannot set the
MTU below 576 bytes due to DHCP communication standards.
To change the MTU size of the packets leaving the external interface:
•
Go to System > Network > IP Address .
•
Click Fragment outgoing packets greater than MTU.
•
Set the maximum MTU size.
Set the maximum packet size in the range of 68 to 1500 bytes. The default MTU size is 1500.
Experiment by lowering the MTU to find an MTU size for maximum performance.
Setting DNS server addresses
Several functions of the DFL-1000, including sending alert emails and URL blocking, use DNS.
To set the DNS server addresses from the web-based manager:
•
Go to System > Config > DNS .
•
Change the primary and secondary DNS server addresses as required.
Controlling management access to the DFL-1000
Use the options on the Management Access page to control access to the DFL-1000 web-based
manager and the CLI through the Internal, External (from the Internet), and DMZ interfaces. Users access
the web-based manager using HTTPS. Users access the CLI remotely using SSH.
•
Go to System > Network > Access .
•
Configure the following parameters for each interface:
HTTPS To allow secure connections to the web-based manager.
PING
If you want the DFL-1000 to respond to pings. Use this setting to verify your installation and for testing.
SSH
If you want to allow secure SSH connections to the CLI.
Configuring any of these settings for the external interface allows remote administration of the DFL-
1000 from any location on the Internet.
•
Click Apply.
DFL-1000 User's Manual
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