Instruction manual

46 UltraLink 2 DVI Installation and Operation Manual
Five buttons are used to modify the Access Control list.
Add – The Add button adds a new entry to the list.
Remove – The Remove button removes a selected entry from the list.
Up – Each press of the Up button moves a selected entry one step up in the list.
Down – Each press of the Down button moves a selected entry one step down the list.
Edit – The Edit button allows the selected entry to be changed.
The Add and Edit buttons display the Host IP Address Filter Screen for adding a new IP address range, or
modifying an existing entry.
Figure 59. Host IP Address Filter Screen
Network/Address:
Enter an IP address to be granted or denied access into this field. If the entry is to be a range of addresses,
one address in the range must be entered here. The complete range will be defined by the net mask.
Mask:
The Mask field holds a net mask used to specify the range of IP addresses along with the IP address entered
in the Network/Address field. A detailed explanation of how these two fields are used to specify an IP address
range follows below.
Access – Allow, Deny:
The Access field determines whether the specified IP range should be allowed or denied access to the
UL2-DVI. Allow puts a + in front of the range to denote that access is allowed. Deny puts a – in front of the
range to indicate that these addresses are not allowed to access the unit.
The IP access control function uses IP address and net mask notation to specify both single locations and
ranges of addresses. In order to use this function correctly, the mask must be calculated so that that it
accurately encompasses the required IP addresses.
Specifying a single address to be allowed or denied access is simple. Enter the desired IP address into the
Network/Address field, and then enter 255.255.255.255 as the Mask. When the number 255 is used
throughout the mask, it means that each bit of the IP address attempting to connect will be compared to the IP
address in the field. Only one address will exactly match the one in the Network/Address field.
To generate a range encompassing ALL addresses, simply use 0.0.0.0 as the mask. This means that none of
the bits of the IP address attempting to connect will be compared to the Network/Address value, so all
addresses are valid. By default, the IP Access Control field includes +0.0.0.0/0.0.0.0 as the first entry. The
purpose of this entry is to allow access to all IP addresses. It is possible to exclude all addresses by using the
Deny option, but this should not be done. It would block all network access, and require resetting the unit to
factory defaults to recover.
The Mask can also be used to define different sized ranges of IP addresses. For any given address,
neighboring addresses can be encompassed in blocks whose sizes are a power of 2 (2
1
= 2, 2
2
= 4, 2
3
= 8, 2
4
= 16, 2
5
= 32, 2
6
= 64, 2
7
= 128), and these must fall on particular boundaries.