Configuring The Encapsulation Type - Cisco ASR 1000 Series Software Configuration Manual

Configuring the Ethernet SPAs

Configuring the Encapsulation Type

By default, the interfaces on the Gigabit Ethernet SPAs support Advanced Research Projects Agency (ARPA)
encapsulation. They do not support configuration of service access point or SNAP encapsulation for transmission
of frames; however, the interfaces will properly receive frames that use service access point and SNAP
encapsulation.
The only other encapsulation supported by the SPA interfaces is IEEE 802.1Q encapsulation for virtual LANs
(VLANs).
Configuring the Autonegotiation on an Interface
Fast Ethernet and Gigabit Ethernet interfaces use a connection-setup algorithm called autonegotiation.
Autonegotiation allows the local and remote devices to configure compatible settings for communication over
the link. Using autonegotiation, each device advertises its transmission capabilities and then agrees upon the
settings to be used for the link.
For the Gigabit Ethernet interfaces on the Cisco ASR 1000 Series Aggregation Services Routers, flow control
is autonegotiated when autonegotiation is enabled. Autonegotiation is enabled by default.
The following guidelines should be followed regarding autonegotiation:
• If autonegotiation is disabled on one end of a link, it must be disabled on the other end of the link. If
• Autonegotiation is not supported on the 10-Port Gigabit Ethernet SPA on the Cisco ASR1000-SIP10.
• Flow control is enabled by default.
• Flow control will be on if autonegotiation is disabled on both ends of the link.
Disabling Autonegotiation
Autonegotiation is automatically enabled and can be disabled on the Fast Ethernet and Gigabit Ethernet
interfaces on the Cisco ASR1000-SIP10. During autonegotiation, advertisement for flow control, speed, and
duplex occurs, depending on the media (fiber or copper) in use. If the interface is connected to a link that has
autonegotiation disabled, autonegotiation should either be re-enabled on the other end of the link or disabled
on the Fast Ethernet or Gigabit Ethernet SPA, if possible. Both ends of the link will not come up properly if
only one end of the link has disabled autonegotiation.
Speed and duplex configurations can be advertised using autonegotiation. However, the only values that are
negotiated are:
• For Fast Ethernet SPAs—100 Mbps for speed and full-duplex mode.
• For Gigabit Ethernet SPAs using RJ-45 copper interfaces—1000 Mbps for speed and full-duplex mode.
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one end of a link has autonegotiation disabled while the other end of the link does not, the link will not
come up properly on both ends.
Link speed is not negotiated when using fiber interfaces.
Cisco ASR 1000 Series Aggregation Services Routers SIP and SPA Software Configuration Guide, Cisco IOS XE
Configuring the Encapsulation Type
Everest 16.5
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