Table Of Contents
Configuring Clocking and Timing
Network Clocking Overview
Precision Timing Protocol (PTP)
Clock Synchronization
Synchronous Ethernet
Synchronous Ethernet ESMC and SSM
Configuring Clocking and Timing
Configuring PTP Clocking
Prerequisites for Configuring PTP Clocking
Configuring an Ordinary Clock
Configuring a Master Ordinary Clock
Configuring a Slave Ordinary Clock
Configuring a Boundary Clock
Configuring PTP Input and Output
Configuration Examples
Configuring Synchronous Ethernet
Configuring an External Clock Source
Configuring Synchronous Ethernet ESMC and SSM
Verifying Clock-Related Settings
Clocking Sample Configurations
Configuring Clocking and Timing
Clock synchronization is important for a variety of applications, including synchronization of radio cell towers. While legacy TDM protocols incorporate timing features, packet-switched networks such as Ethernet do not natively include these features. The Cisco ME 3600X 24CX Series Switch supports legacy TDM technologies while supporting a variety of technologies that distribute clocking information over packet-switched networks.
The following sections describe the clocking and timing features available on the Cisco ME 3600X 24CX Series Switch.
•
Network Clocking Overview
•Configuring Clocking and Timing
•Clocking Sample Configurations
Network Clocking Overview
Clocking is typically distributed from the core network outward to the BTS or Node B at the network edge. The Cisco ME 3600X 24CX Series Switch receives and transmits clocking information using any of the following ports:
•T1/E1
•GigabitEthernet
•BITS/SYNC port
•1PPS
•10Mhz
•ToD
The Cisco ME 3600X 24CX Series Switch supports the following clocking types:
•Precision Timing Protocol (PTP)
•Synchronous Ethernet
Precision Timing Protocol (PTP)
The Cisco ME 3600X 24CX Series Switch supports the Precision Time Protocol (PTP) as defined by the IEEE 1588-2008 standard. PTP provides for accurate time synchronization on over packet-switched networks. Nodes within a PTP network can act in one of the following roles:
•Ordinary clock—An ordinary clock is a 1588 clock with a single PTP port that can serve in one of the following roles:
–Master mode—Distributes timing information over the network to one or more slave clocks, thus allowing the slave to synchronize its clock to the master.
–Slave mode—Synchronizes its clock to a master clock. You can enable slave clocking on up to two interfaces simultaneously in order to connect to two different master clocks.
•Boundary clock—The device participates in selecting the best master clock and can act as the master clock if no better clocks are detected.
Note The Cisco ME 3600X 24CX Series Switch does not currently act as a transparent clock.
The 1588-2008 standard defines other clocking devices that are not described here.
Note When a shut/no shut is carried on the loopback interface, the PTP port is deleted and recreated. This causes the PTP counters to reset.
Clock Synchronization
PTP master devices periodically launch an exchange of messages with slave devices to help each slave clock recompute the offset between its clock and the master clock. Periodic clock synchronization mitigates any drift between the master and slave clocks.
Synchronous Ethernet
Synchronous Ethernet is a timing technology that allows the Cisco ME 3600X 24CX Series Switch switch to transport frequency information over Ethernet. Because frequency is embedded in Ethernet packets, synchronous Ethernet must be supported by each network element in the synchronization path. Synchronous Ethernet is defined in the ITU-T G.781, G.8261, G.8262, and G.8264, Telcordia GR-253-CORE, and Telcordia GR-1244-CORE standards.
Synchronous Ethernet ESMC and SSM
The Cisco ME 3600X 24CX Series Switch supports Ethernet Synchronization Message Channel (ESMC) and Synchronization Status Message (SSM) to provide clock synchronization on Synchronous Ethernet. For more information about Ethernet ESMC and SSM, see Chapter 5 "Configuring Clocking and Timing."
Note SSM is only supported on BITS interface.
Configuring Clocking and Timing
The Cisco ME 3600X 24CX Series Switch switch supports the following network clocking types:
•Precision Time Protocol (PTP)—Clocking and clock recovery based on the IEEE 1588-2008 standard; allows the Cisco ME 3600X 24CX Series Switch switch to receive clocking from another PTP-enabled device or provide clocking to a PTP-enabled device. To configure PTP clocking, see Configuring PTP Clocking.
•Synchronous Ethernet—Allows the network to transport frequency and time information over Ethernet. To configure synchronous Ethernet, see Configuring Synchronous Ethernet.
•Verifying Clock Settings—To verify a clocking configuration, see Verifying Clock-Related Settings.
Configuring PTP Clocking
This section describes how to configure PTP-based clocking on the Cisco ME 3600X 24CX Series Switch.
•Prerequisites for Configuring PTP Clocking
•Configuring an Ordinary Clock
•Configuring a Boundary Clock
Note The settings shown in this section are an example only; you must determine the appropriate PTP settings based upon your network clocking design.
Note The configuration sections describing the 1PPS and 10Mhz timing ports only apply to the Cisco ME 3600X-24CX switch.
Prerequisites for Configuring PTP Clocking
To enable PTP v2 Ordinary Slave Clock, one of the following base licenses must be installed on the switch:
•Metro IP Access
•Advanced Metro IP Access
An additional 1588 feature license is required to enable the Ordinary master clock and boundary clock functionality.
You must reload the switch to activate the license.
Configuring an Ordinary Clock
The followign sections describe how to cofigure the switch as an ordinary clock.
•Configuring a Master Ordinary Clock
•Configuring a Slave Ordinary Clock
Configuring a Master Ordinary Clock
Enter the following commands to configure the switch to act as a master ordinary clock:
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Command
|
Purpose
|
Step 1
|
enable
Example:
Switch> enable
|
Enables privileged EXEC mode.
•Enter your password if prompted.
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Step 2
|
configure terminal
Example:
Switch# configure terminal
|
Enters global configuration mode.
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Step 3
|
ptp clock {ordinary | boundary |
e2e-transparent} domain
domain-number [hybrid]
Example:
Switch(config)# ptp clock ordinary
domain 0
|
Configures the PTP clock. You can create the following clock types:
·Ordinary—A 1588 clock with a single PTP port that can operate in Master or Slave mode.
·Boundary—Participates in selecting the best master clock and can act as the master clock if no better clocks are detected.
Note The transparent clock and hybrid mode are not supported on the Cisco ME 3600X 24CX switch.
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Step 4
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priority1 priorityvalue
Example:
Switch(config-ptp-clk)# priority1
128
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Sets the preference level for a clock. Slave devices use the priority1 value when selecting a master clock: a lower priority1 value indicates a preferred clock. The priority1 value is considered above all other clock attributes.
Valid values are from 0-255. The default value is 128.
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Step 5
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priority2 priorityvalue
Example:
Switch(config-ptp-clk)# priority2
128
|
Sets a secondary preference level for a clock. Slave devices use the priority2 value when selecting a master clock: a lower priority2 value indicates a preferred clock. The priority2 value is considered only when the router is unable to use priority1 and other clock attributes to select a clock.
Valid values are from 0-255. The default value is 128.
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Step 6
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clock-port port-name {master | slave}
Example:
Switch(config-ptp-clk)# clock-port
Master master
Router(config-ptp-port)#
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Sets the clock port to PTP master or slave mode; in master mode, the port exchanges timing packets with PTP slave devices.
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Step 7
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transport ipv4 unicast interface interface-type interface-number [negotiation]
Example:
Switch(config-ptp-port)# transport ipv4 unicast interface loopback 0 negotiation
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Sets port transport parameters.
The negotiation keyword configures the router to discover a PTP master clock from all available PTP clock sources.
Note PTP redundancy is supported only on unicast negotiation mode.
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Step 8
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clock-destination destination-address
Example:
Switch(config-ptp-port)# clock-destination 8.8.8.1
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Specifies the IP address of a clock destination when the router is in PTP master mode.
•The destination-address parameter is required in master mode.
•The destination-address parameter is the loopback address of the slave clock.
Note The clock-destination command is not applicable in unicast negotiation mode.
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Step 9
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sync interval value
Example:
Switch(config-ptp-port)# sync interval 1
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Specifies the sync interval.
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Step 10
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announce timeout value
Example:
Switch(config-ptp-port)# announce timeout 8
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Specifies the number of PTP announcement intervals before the session times out. Valid values are 1-10.
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Step 11
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exit
Example:
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Exits configuration mode.
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Configuring a Slave Ordinary Clock
Follow these steps to configure the switch to act as a slave ordinary clock.
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Command
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Purpose
|
Step 1
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Switch# configure terminal
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Enter configuration mode.
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Step 2
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ptp clock {ordinary | boundary | e2e-transparent} domain domain-number [hybrid]
Example:
Switch(config)# ptp clock ordinary
domain 0
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Configures the PTP clock. You can create the following clock types:
•Ordinary—A 1588 clock with a single PTP port that can operate in Master or Slave mode.
•Boundary—Participates in selecting the best master clock and can act as the master clock if no better clocks are detected.
Note The transparent clock and hybrid mode are not supported on the Cisco ME 3600X 24CX switch.
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Step 3
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priority1 priorityvalue
Example:
Switch(config-ptp-clk)# priority1
128
|
Sets the preference level for a clock. Slave devices use the priority1 value when selecting a master clock: a lower priority1 value indicates a preferred clock. The priority1 value is considered above all other clock attributes.
Valid values are from 0-255. The default value is 128.
|
Step 4
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priority2 priorityvalue
Example:
Switch(config-ptp-clk)# priority2 128
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Sets a secondary preference level for a clock. Slave devices use the priority2 value when selecting a master clock: a lower priority2 value indicates a preferred clock. The priority2 value is considered only when the router is unable to use priority1 and other clock attributes to select a clock.
Valid values are from 0-255. The default value is 128.
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Step 5
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clock-port port-name {master | slave}
Example:
Switch(config-ptp-clk)# clock-port
Slave slave
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Sets the clock port to PTP master or slave mode; in slave mode, the port exchanges timing packets with a PTP master clock.
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Step 6
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transport ipv4 unicast interface interface-type interface-number [negotiation]
Example:
Switch(config-ptp-port)# transport
ipv4 unicast interface loopback 0
negotiation
|
Sets port transport parameters.
The negotiation keyword configures the router to discover a PTP master clock from all available PTP clock sources.
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Step 7
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clock-source source-address
Example:
Switch(config-ptp-port)#
clock-source 8.8.8.1
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Specifies the address of a PTP master clock.
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Step 8
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sync interval value
Example:
Switch(config-ptp-port)# sync interval 1
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Specifies the sync interval.
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Step 9
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announce timeout value
Example:
Switch(config-ptp-port)# announce
timeout 8
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Specifies the number of PTP announcement intervals before the session times out. Valid values are 1-10.
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Step 10
|
delay-req interval interval
Example:
Switch(config-ptp-port)# delay-req
interval 1
|
Configures the minimum interval allowed between PTP delay-request messages when the port is in the master state.
The intervals are set using log base 2 values, as follows:
•3—1 packet every 8 seconds
•2—1 packet every 4 seconds
•1—1 packet every 2 seconds
•0—1 packet every second
•-1—1 packet every 1/2 second, or 2 packets per second
•-2—1 packet every 1/4 second, or 4 packets per second
•-3—1 packet every 1/8 second, or 8 packets per second
•-4—1 packet every 1/16 seconds, or 16 packets per second.
•-5—1 packet every 1/32 seconds, or 32 packets per second.
•-6—1 packet every 1/64 seconds, or 64 packets per second.
•-7—1 packet every 1/128 seconds, or 128 packets per second.
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Step 11
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Router(config-ptp-port)# end
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Exit configuration mode.
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Configuring a Boundary Clock
Follow these steps to configure the switch to act as a boundary clock.
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Command
|
Purpose
|
Step 1
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Switch# configure terminal
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Enter configuration mode.
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Step 2
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Router(config)# ptp clock {ordinary | boundary | e2e-transparent} domain domain-number [hybrid]
Example:
Switch(config)# ptp clock boundary
domain 0
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Configures the PTP clock. You can create the following clock types:
•Ordinary—A 1588 clock with a single PTP port that can operate in Master or Slave mode.
•Boundary—Participates in selecting the best master clock and can act as the master clock if no better clocks are detected.
Note The transparent clock and hybrid mode are not supported on the Cisco ME 3600X 24CX switch.
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Step 3
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clock-port port-name {master | slave}
Example:
Switch(config-ptp-clk)# clock-port
SLAVE slave
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Sets the clock port to PTP master or slave mode; in slave mode, the port exchanges timing packets with a PTP master clock.
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Step 4
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transport ipv4 unicast interface interface-type interface-number [negotiation]
Example:
Switch(config-ptp-port)# transport
ipv4 unicast interface Loopback 0
negotiation
|
Sets port transport parameters.
The negotiation keyword configures the router to discover a PTP master clock from all available PTP clock sources.
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Step 5
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clock-source source-address [priority]
Example:
Switch(config-ptp-port)# clock
source 133.133.133.133
|
Specifies the address of a PTP master clock. You can specify a priority value as follows:
•No priority value—Assigns a priority value of 0.
•1—Assigns a priority value of 1.
•2—Assigns a priority value of 2, the highest priority.
Note This command is optional if PTP is configured in unicast negotiation mode.
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Step 6
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clock-port port-name {master | slave}
Example:
Switch(config-ptp-port)# clock-port
Master master
|
Sets the clock port to PTP master or slave mode; in master mode, the port exchanges timing packets with PTP slave devices.
Note The master clock-port does not establish a clocking session until the slave clock-port is phase aligned.
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Step 7
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transport ipv4 unicast interface interface-type interface-number [negotiation]
Example:
Switch(config-ptp-port)# transport
ipv4 unicast interface Loopback 1
negotiation
|
Sets port transport parameters.
The negotiation keyword configures the router to discover a PTP master clock from all available PTP clock sources.
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Step 8
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Switch(config-ptp-port)# end
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Exit configuration mode.
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Configuring PTP Input and Output
You can use the 1pps, 10Mhz and BITS timing ports on the Cisco ME 3600X-24CX to do the following:
•Provide or receive 1PPS time of day messages
•Provide output clocking at 10Mhz, 2.048Mhz, and 1.544Mhz
•Receive input clocking at 10Mhz, 2.048Mhz, and 1.544Mhz
Note This section applies only to the Cisco ME 3600X-24CX.
The following section describes how to configure time of day messages, output clocking, and input clocking in master clock mode.
•If you want to configure input clocking using the 10Mhz or BITS timing port, use the following command:
–Use the network-clock input-source command to enable input clocking at 10Mhz, 2.048Mhz, or 1.544Mhz.
Switch(config)# network-clock input-source 2 external 1/0/0 10m
Input clocking applies when the switch is in master mode.
•To configure output clocking using the 10Mhz or BITS timing port, use the network-clock output-source command to specify 10Mhz, 2.048Mhz, or 1.544Mhz output. Use this command when the switch is in slave mode.
Switch(config)# network-clock output-source system 2 external 1/0/0 10m
•To configure the switch to send time of day messages using the 1PPS port, use the output 1pps command. Use the input or output parameters to specify the direction.
Switch(config)# ptp clock ordinary domain 0
Switch(config-ptp-clk)# output 1pps 0/0
Note Input 1pps is only supported in master mode. Output 1pps configuration is supported in slave or boundary clock mode.
•To configure the time of day message format, use the tod command.
Switch(config)# ptp clock ordinary domain 0
Switch(config-ptp-clk)# tod 0/0 ubx
Configuration Examples
Use commands below for input and output.
network-clock input-source 2 external 1/0/0 10m
Switch(config)#network-clock input-source 2 external 1/0/0 ?
2048k Option 1 2048kHz on BITS/SSU port
Tod and 1pps configuration.
Master:
Switch(config)#ptp clock ordinary domain 0
Switch(config-ptp-clk)#input 1pps 0/0
Switch(config-ptp-clk)#tod 0/0 ?
cisco Set TOD format to CISCO
nmea Set TOD format to NMEA ZDA
ntp Set TOD format to NTP
ubx Set TOD format to UBX
Slave:
Switch(config)#ptp clock ordinary domain 0
Switch(config-ptp-clk)#output 1pps 0/0 ?
offset 1PPS output offset
pulse-width 1PPS output pulse width
Switch(config-ptp-clk)#tod 0/0 ?
cisco Set TOD format to CISCO
nmea Set TOD format to NMEA ZDA
ntp Set TOD format to NTP
ubx Set TOD format to UBX
Note To see further configuration examples for input and output timing, see Clocking Sample Configurations.
Configuring Synchronous Ethernet
The following sections describe how to configure synchronous Ethernet timing on the Cisco ME 3600X 24CX Series Switch switch.
Note Hybrid mode is not supported therefore, network-clock input-source command cannot be configured with Ordinary Slave mode or Boundary Clock mode.
Configuring an External Clock Source
To configure an external clock source using Synchronous Ethernet, use the network-clock input-source priority external 1/0/0 {{E1 {crc4 | cas |fas}} {T1 {d4 | sf | esf}} } command.
Switch(config)# network-clock input-source 1 external 1/0/0
Configuring Synchronous Ethernet ESMC and SSM
For instructions on how to configure synchronous Ethernet Synchronization Message Channel (ESMC)and Synchronization Status Message (SSM), see Configuring Synchronous Ethernet in Cisco ME 3800x and ME 3600x Switch Software Configuration Guide
Verifying Clock-Related Settings
Use the following commands to verify the clock settings:
•show ptp clock dataset
•show ptp port dataset
•show ptp clock running
•show platform ptp all
For more information about these commands, see the Cisco ME 3800X and ME 3600X Switch Command Reference, Release 15.2(4)S.
Clocking Sample Configurations
The following sections show a sample configurations for clocking features on the switch.
Ordinary Clock—Slave
ptp clock ordinary domain 0
transport ipv4 unicast interface loopback 0 negotiation
Ordinary Clock—Master
ptp clock ordinary domain 0
transport ipv4 unicast interface loopback 0 negotiation
Unicast Configuration—Slave Mode
ptp clock ordinary domain 0
transport ipv4 unicast interface loopback 0
Unicast Configuration—Master Mode
ptp clock ordinary domain 0
transport ipv4 unicast interface loopback 0
clock-destination 8.8.8.2
Unicast Negotiation—Slave
ptp clock ordinary domain 0
transport ipv4 unicast interface Loopback0 negotiation
Unicast Negotiation—Master
ptp clock ordinary domain 0
transport ipv4 unicast interface Loopback0 negotiation
Boundary Clock
ptp clock boundary domain 0
transport ipv4 unicast interface Loopback0 negotiation
transport ipv4 interface Loopback1 negotiation
Clock Selection Parameters
network-clock synchronization automatic
network-clock synchronization mode QL-enabled
network-clock input-source 1 external 1/0/0 10m
ToD/1PPS Configuration—Master
network-clock input-source 1 external 1/0/0 10m
ptp clock ordinary domain 0
transport ipv4 unicast interface loopback 0
ToD/1PPS Configuration—Slave
ptp clock ordinary domain 0
transport ipv4 unicast interface loopback 0 negotiation
Show Commands
Router# show ptp clock dataset ?
current currentDS dataset
default defaultDS dataset
time-properties timePropertiesDS dataset
Router#show ptp port dataset ?
foreign-master foreignMasterDS dataset
Router#show ptp clock running domain 0
PTP Ordinary Clock [Domain 0]
State Ports Pkts sent Pkts rcvd Redundancy Mode
ACQUIRING 1 98405 296399 Track one
Name Tx Mode Role Transport State Sessions Port
Addr
SLAVE unicast slave Lo0 Slave 1
8.8.8.8
Peer addr Pkts in Pkts out In Errs Out Errs
Router#show platform ptp all
Slave info : [Loopback0][0x38A4766C]
--------------------------------
Slave Port hdl : 486539266
Tx Mode : Unicast-Negotiation
Configured-Flags : 0x7F - Clock Port Stream
Config-Ready-Flags : Port Stream
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