bpdu-tunnel Configuration
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13. bpdu-tunnel Configuration
13.1
Introduction to bpdu-tunnel
BPDU Tunnel is a Layer 2 tunnel technology. It allows Layer 2 protocol packets of
geographically dispersed private network users to be transparently transmitted over
specific tunnels across a service provider network.
13.1.1
bpdu-tunnel function
In MAN application, multi-branches of a corporation may connect with each other by
the service provider network. VPN provided by the service provider enables the
geographically dispersed networks to form a local LAN, so the service provider needs to
provide the tunnel function, namely, data information generated by user‘s network is able
to inextenso arrive at other networks of the same corporation through the service provider
network. To maintain a local concept, it not only needs to transmit the data within the
user‘s private network across the tunnel, but also transmit layer 2 protocol packets within
the user‘s private network.
13.1.2
Background of bpdu-tunnel
Special lines are used in a service provider network to build user-specific Layer 2
networks. As a result, a user network is broken down into parts located at different sides of
the service provider network. As shown in Figure, User A has two devices (CE 1 and CE 2)
and both devices belong to
the same VLAN. User‘s network is divided into network 1 and
network 2, which are connected by the service provider network. When Layer 2 protocol
packets cannot implement the passthrough across the service provider network, the
user‘s network cannot process independent Layer 2 protocol calculation (for example,
spanning tree calculation), so they affect each other.