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11-10
Using Authorized IP Managers
Building IP Masks
Configuring Multiple Stations Per Authorized Manager
IP Entry
The mask determines whether the IP address of a station on the network meets
the criteria you specify. That is, for a given Authorized Manager entry, the
switch applies the IP mask to the IP address you specify to determine a range
of authorized IP addresses for management access. As described above, that
range can be as small as one IP address (if 255 is set for all octets in the mask),
or can include multiple IP addresses (if one or more octets in the mask are set
to less than 255).
If a bit in an octet of the mask is “on” (set to 1), then the corresponding bit in
the IP address of a potentially authorized station must match the same bit in
the IP address you entered in the Authorized Manager IP list. Conversely, if a
bit in an octet of the mask is “off” (set to 0), then the corresponding bit in the
IP address of a potentially authorized station on the network does not have to
match its counterpart in the IP address you entered in the Authorized Manager
IP list. Thus, in the example shown above, a “255” in an IP Mask octet (all bits
in the octet are “on”) means only one value is allowed for that octet—the value
you specify in the corresponding octet of the Authorized Manager IP list. A “0”
(all bits in the octet are “off”) means that any value from 0 to 255 is allowed
in the corresponding octet in the IP address of an authorized station. You can
also specify a series of values that are a subset of the 0-255 range by using a
value that is greater than 0, but less than 255.
Figure 11-5. Analysis of IP Mask for Multiple-Station Entries
1st
Octet
2nd
Octet
3rd
Octet
4th
Octet
Manager-Level or Operator-Level Device Access
IP Mask 255 255 255 0 The “255” in the first three octets of the mask specify that only the exact
value in the octet of the corresponding IP address is allowed. However,
the zero (0) in the 4th octet of the mask allows any value between 0 and
255 in that octet of the corresponding IP address. This mask allows switch
access to any device having an IP address of 10.28.227.xxx, where xxx is
any value from 0 to 255.
Authorized
Manager IP
10 28 227 125
IP Mask 255 255 255 249 In this example (figure 11-6, below), the IP mask allows a group of up to
4 management stations to access the switch. This is useful if the only
devices in the IP address group allowed by the mask are management
stations. The “249” in the 4th octet means that bits 0 and 3 - 7 of the 4th
octet are fixed. Conversely, bits 1 and 2 of the 4th octet are variable. Any
value that matches the authorized IP address settings for the fixed bits is
allowed for the purposes of IP management station access to the switch.
Thus, any management station having an IP address of 10.28.227.121
, 123,
125
, or 127 can access the switch.
Authorized
IP Address
10 28 227 125