Cisco ASR 920 series, Руководство по настройке Ethernet-маршрутизатора

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C H A P T E R
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Configuring IEEE 802.1ad
Provider networks handle traffic from a large number of customers. It is important that one customer
’
s traffic
is isolated from the other customer ’ s traffic.
IEEE 802.1ad enables the service providers to use the architecture and protocols of IEEE 802.1Q to offer
separate LANs, bridged local area networks, or virtual bridged local area networks to a number of customers,
with minimal cooperation or no cooperation between each customer and the service provider.
IEEE 802.1ad implements standard protocols for double tagging of data. The data traffic coming from the
customer side are double tagged in the provider network where the inner tag is the customer-tag (C-tag) and
the outer tag is the provider-tag (S-tag). The control packets are tunneled by changing the destination MAC
address in the provider network.
A service provider's Layer 2 network transports the subscriber's Layer 2 protocols transparently. Provider
Bridge allows the service provider switches to transparently carry customer Layer 2 control frames, such as
spanning tree Bridge Protocol Data Units (BPDUs) or Cisco proprietary protocol frames such as Cisco
Discovery Protocol (CDP) without mixing the service provider's own traffic and with other customer traffic
in the service provider's network. A provider bridge is just like a standard 802.1Q bridge, but it imposes a
set of requirements, defined by IEEE 802.1ad standards, on a port in a provider bridge which interfaces to
customer. This port is a UNI Port. 802.1ad Provider Bridge thus achieves the same functionality as being
addressed with L2PT and QinQ.
When Connectivity Fault Management (CFM) is configured on 802.1ad interfaces, all CFM, Link Ethernet
Operations, Administration, and Maintenance (OAM), Enhanced Local Management Interface (ELMI) or
Y.1731 performance monitoring packets have their own peer or data rules depending on the type of 802.1ad
port configured.
• Finding Feature Information, page 402
• Prerequisites for 802.1ad, page 402
• Restrictions for 802.1ad, page 402
• Information About 802.1ad, page 403
• How to Configure 802.1ad, page 409
• Verifying IEEE 802.1ad, page 416
• Additional References, page 417
• Feature Information for IEEE 802.1ad, page 418
Carrier Ethernet Configuration Guide (Cisco ASR 920 Series)
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