Model 5601MSC
Model 5601MSC Master SPG/Master Clock System
MASTER CLOCK
Revision 2.2
Page - 151
4.5.13.2. Configuring the NTP Restrictions
Restrictions define which IP addresses will be ignored by the NTP server. There are 8 restriction entries
allowed, and they are additive. By default, all IP addresses are permitted to query the NTP server. Each
restriction can block an IP address or range of IP addresses.
Each restriction is specified by an IP address, and a mask. The mask is compared to the IP address in
binary format. Every bit that is set to a 0 in the mask acts as a “don’t care”. Note that 255 is equivalent
to 11111111 in binary. Some examples are given below:
To restrict a single IP address (e.g. 172.21.1.70), set the mask to all 1’s
Restrict IpAdd = 172.21.1.70
Restrict IpMsk=255.255.255.255
To restrict all IP addresses beginning with a certain prefix (e.g. 172.21.1.XXX):
Restrict IpAdd = 172.21.1.0
Restrict IpMsk=255.255.255.0
For the sake of simplicity in the manual, only the menu items for restriction 1 will be shown.
4.5.13.2.1.
Setting the NTP Restriction Mode
GENERAL
This item is used to enable or disable the current restriction rule. Set it to
permit
to effectively disable the rule, or set it to
deny
to apply the rule to
incoming NTP traffic.
NTP rules
NTP restricts1
Restrict mode
Restrict permit
Restrict deny
4.5.13.2.2.
Setting the NTP Restriction IP Address
GENERAL
This menu item is used to enter the IP Address portion of the restriction
rule. It is used with the IP Mask to determine the range of IP addresses that
will be ignored by the NTP server. Only effective when the Restrict mode is
set to
deny
.
NTP rules
NTP restricts1
Restrict IpAdd
Restrict IpAdd
172.21.1.70