PTP configuration and mode limitations

• The Cisco PTP implementation supports only two-step clock operation in BC mode; one-step clock is not supported.

• In transparent clock mode, the switch converts any one-step Sync message received from the grandmaster clock into a two-step message.

• Cisco PTP supports multicast PTP messages only.

• The switch and the grandmaster clock must be in the same PTP domain.

• When Power Profile mode is enabled, the switch drops the PTP announce messages that do not include these two Type, Length, Value (TLV) message extensions: Organization_extension and Alternate_timescale.

  If the grandmaster clock is not compliant with PTP and sends announce messages without these TLVs, configure the switch to process the announce message by entering the PTPallow-without-TLV command.

  Refer to Configure PTP power profile mode on the switch for a complete description of this command.

• When the switch is in Power Profile mode, only the peer_delay mechanism is supported.

  To change to boundary clock mode and the peer_delay mechanism, enter the PTPmodeboundarypdelay-req command.

• In Default Profile mode, only the delay_request mechanism is supported.

  To change to boundary clock mode with the delay_request mechanism, enter the PTP mode boundary delay-req command.

• The packet format for PTP messages can be 802.1q tagged packets or untagged packets.

• The switch does not support 802.1q QinQ tunneling.

• In switch Power Profile mode:

  • When the PTP interface is configured as an access port, PTP messages are sent as untagged, Layer 2 packets.

  • When the PTP interface is configured as a trunk port, PTP packets are sent as 802.1q tagged Layer 2 packets over the port native VLAN.

• Time recipient IEDs must support tagged and untagged packets.

• When PTP packets are sent on the native VLAN in E2E transparent clock mode, they are sent as untagged packets. To configure the switch to send them as tagged packets, enter the global VLANdot1qtagnative command.

• Sets the PTP VLAN on a trunk port. The range is from 1 to 4094. The default is the native VLAN of the trunk port.

• In boundary mode, only PTP packets in PTP VLAN will be processed, PTP packets from other VLANs will be dropped.

• Before configuring the PTP VLAN on an interface, the PTP VLAN must be created and allowed on the trunk port.

• Most grandmaster clocks use the default VLAN 0. In Power Profile mode, the switch default VLAN is VLAN 1 and VLAN 0 is reserved. When you change the default grandmaster clock VLAN, it must be changed to a VLAN other than 0.

• When VLAN is disabled on the grandmaster clock, the PTP interface must be configured as an access port.

• All PHY PTP clocks are synchronized to the grandmaster clock. The system clock of the switch is not synchronized during PTP configuration or operation.

• When VLAN is enabled on the grandmaster clock, it must be in the same VLAN as the native VLAN of the PTP port on the switch.

• Grandmaster clocks can drop untagged PTP messages when a VLAN is configured on the grandmaster clock. To force the switch to send tagged packets to the grandmaster clock, enter the global VLANdot1qtagnative command.

Boundary Clock Mode

• You can enable this mode when the switch is in Power Profile mode (Layer 2) or in Default Profile mode (Layer 3).

Forward Mode

• You can enable this mode when the switch is in Power Profile mode (Layer 2) or in Default Profile mode (Layer 3).

• When the switch is in Forward mode, the only global configuration available is the CLI command to switch to a different PTP mode (that is, boundary, e2etransparent, or p2ptransparent).

E2E Transparent Clock Mode

• You can enable this mode only when the switch is in Default Profile mode (Layer 3).

• When the switch is in E2E Transparent mode, the only global configurations available from CLI commands are to switch to a different PTP mode (boundary, forward, or GMC-BC), and change the domain.

P2P Transparent Clock Mode

• You can enable this mode only when the switch is in Power Profile mode (Layer 2).

GMC-BC Clock Mode

• You can enable this mode when the switch is in Default Profile mode or in Power Profile mode.

Adaptive mode (ptp transfer filter adaptive ) is not available in Power Profile mode.

PTP clock mode limitations with EtherChannels and VLANs.

The NTP to PTP feature supports the Default E2E Profile and Power Profile.

To mitigate potential CRC errors on the Cisco IE3105 platform following a device reload, ensure that autonegotiation settings are consistent across both ends of the link (either enabled or disabled on both sides). We also recommend either replacing the speed auto 100 command with speed 100 duplex full or configuring speed auto 100 at both ends.