Date created: Monday, October 7, 2019 8:01:06 AM. Last modified: Friday, January 12, 2024 5:50:50 PM

Ports, SAPs, Encap Type

Port Modes:

Access ports - Configured for customer facing traffic on which services are configured. If a Service Access Port (SAP) is to be configured on the port, it must be configured as an access port. When a port is configured for access mode, the appropriate encapsulation type must be configured to distinguish the services on the port. Once a port has been configured for access mode, one or more services can be configured on the port depending on the encapsulation value.

Access-uplink ports - With this option, the encap-type can be configured to only qinq. Access-uplink SAPs, which are QinQ SAPs, can only be configured on an access uplink port to allow the operator to differentiate multiple services being carried over a single access uplink port. This is the default mode when a node is operating in access-uplink mode.

Network ports - These ports participate in the service provider transport or infrastructure network. Dot1q is supported on network ports. This is default for nodes operating in network mode.

Hybrid ports - Configured for access and network facing traffic. While the default mode of an Ethernet port remains network, the mode of a port cannot be changed between the access/network/hybrid values unless the port is shut down and the configured SAPs and/or interfaces are deleted. Hybrid ports allow a single port to operate in both access and network modes. MTU of port in hybrid mode is the same as in network mode except for the 10/100 MDA. The default encap for hybrid port mode is dot1q, it also supports QinQ encapsulation on the port level. Null hybrid port mode is not supported.

Once the port is changed to hybrid, the default MTU of the port is changed to match the value of 9212 bytes currently used in network mode (higher than an access port); this is to ensure that both SAP and network VLANs can be accommodated. The only exception is when the port is a 10/100 fast Ethernet. In those cases, the MTU in hybrid mode is set to 1522 bytes, which corresponds to the default access MTU with QinQ, which is larger than the network dot1q MTU or access dot1q MTU for this type of Ethernet port...An Ethernet port configured in hybrid mode can have two values of encapsulation type: dot1q and QinQ. The NULL value is not supported since a single SAP is allowed and can be achieved by configuring the port in the access mode, or a single network IP interface is allowed, which can be achieved by configuring the port in network mode.


A Service Access Point (SAP) can only be configured on an access port. When a port is configured for access mode, the appropriate encap-type must be specified to distinguish the services on the port.


Encap Types and Ethertypes:
dot1q — Ingress frames carry 802.1Q tags where each tag signifies a different service.
null — Ingress frames will not use any tags to delineate a service. As a result, only one service can be
configured on a port with a null encapsulation type.
qinq — This encapsulation type is specified for QinQ access SAPs

Defaults VLAN Ethertypes:
If the encap-type is dot1p, then the default is 0x8100.
If the encap-type is qinq, then the default is 0x8100.

CLI from 7210 SAS-X:

show port x/x/x
Dot1Q Ethertype : 0x8100 QinQ Ethertype : 0x8100