Cisco 15327 - Manual (Page 143)

9-9
Ethernet Card Software Feature and Configuration Guide, R7.2
Chapter 9 Configuring IEEE 802.1Q Tunneling and Layer 2 Protocol Tunneling
Understanding Layer 2 Protocol Tunneling
interface POS1
no ip address
crc 32
!
interface POS1.1
encapsulation dot1Q 10
bridge-group 10
!
interface POS1.3
encapsulation dot1Q 30
bridge-group 30
Example 9-5 applies to ML-Series card C.
Example 9-5 ML-Series Card C Configuration
hostname ML-C
bridge 10 protocol rstp
!
!
interface GigabitEthernet0
no ip address
no ip route-cache
mode dot1q-tunnel
bridge-group 10
bridge-group 10 spanning-disabled
!
interface POS0
no ip address
no ip route-cache
crc 32
!
interface POS0.1
encapsulation dot1Q 10
no ip route-cache
bridge-group 10
Understanding Layer 2 Protocol Tunneling
Customers at different sites connected across a service-provider network need to run various Layer 2
protocols to scale their topology to include all remote sites, as well as the local sites. Spanning Tree
Protocol (STP) must run properly, and every VLAN should build a proper spanning tree that includes the
local site and all remote sites across the service-provider infrastructure. Cisco Discovery Protocol (CDP)
must discover neighboring Cisco devices from local and remote sites. VLAN Trunking Protocol (VTP)
must provide consistent VLAN configuration throughout all sites in the customer network.
When protocol tunneling is enabled, edge switches on the inbound side of the service-provider
infrastructure encapsulate Layer 2 protocol packets with a special MAC address and send them across
the service-provider network. Core switches in the network do not process these packets, but forward
them as normal packets. CDP, STP, or VTP Layer 2 protocol data units (PDUs) cross the
service-provider infrastructure and are delivered to customer switches on the outbound side of the
service-provider network. Identical packets are received by all customer ports on the same VLANs with
the following results:
• Users on each of a customer’s sites are able to properly run STP and every VLAN can build a correct
spanning tree based on parameters from all sites and not just from the local site.