The IP Mask parameter controls how the switch uses an Authorized manager IP value to recognize the IP addresses of authorized manager stations on your network.
This is the easiest way to apply a mask. If you have ten or fewer management and/or operator stations, you can configure them by adding the address of each to the Authorized manager IP list with 255.255.255.255 for the corresponding mask. For example, as shown in The show authorized-managers command with access method configured, if you configure an IP address of 10.28.227.125 with an IP mask of 255.255.255.255, only a station having an IP address of 10.28.227.125 has management access to the switch.
Analysis of IP Mask for Single-Station Entries
| 1st Octet | 2nd Octet | 3rd Octet | 4th Octet | manager-Level or operator-Level Device Access | |
|---|---|---|---|---|---|
| IP Mask | 255 | 255 | 255 | 255 | The “255” in each octet of the mask specifies that only the exact value in that octet of the corresponding IP address is allowed. This mask allows management access only to a station having an IP address of 10.33.248.5. |
| Authorized manager IP | 10 | 28 | 227 | 125 |
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.
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 (How the Bitmap in the IP Mask defines Authorized manager addresses, 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 manager IP | 10 | 28 | 227 | 125 |
Additional examples for authorizing multiple stations
| Entries for authorized manager list | Results | ||||
|---|---|---|---|---|---|
| IP mask | 255 | 255 | 0 | 255 | This combination specifies an authorized IP address of 10.33.xxx.1. It could be applied, for example, to a subnetted network where each subnet is defined by the third octet and includes a management station defined by the value of "1" in the fourth octet of the station's IP address. |
| Authorized manager IP | 10 | 33 | 248 | 1 | |
| IP mask | 255 | 238 | 255 | 250 | Allows 230, 231, 246, and 247 in the 2nd octet, and 194, 195, 198, 199 in the 4th octet. |
| Authorized manager IP | 10 | 247 | 100 | 195 | |