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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter 31 Configuring IP Unicast Routing
Configuring Multi-VRF CE
sites participate in the same VPN. Each VPN is mapped to a specified VRF. After learning local
VPN routes from CEs, a PE router exchanges VPN routing information with other PE routers by
using internal BGP (IBPG).
•
Provider routers or core routers are any routers in the service provider network that do not attach to
CE devices.
With multi-VRF CE, multiple customers can share one CE, and only one physical link is used between
the CE and the PE. The shared CE maintains separate VRF tables for each customer and switches or
routes packets for each customer based on its own routing table. Multi-VRF CE extends limited PE
functionality to a CE device, giving it the ability to maintain separate VRF tables to extend the privacy
and security of a VPN to the branch office.
shows a configuration where each Catalyst 3550 switch acts as multiple virtual CEs. This
scenario is suited for customers who have low bandwidth requirements for their VPN service, for
example, small companies. In this case, multi-VRF CE support is required in the Catalyst 3550 switches.
Because multi-VRF CE is a Layer 3 feature, each interface in a VRF must be a Layer 3 interface.
Figure 31-6 Catalyst 3550 Switches Acting as Multiple Virtual CEs
When the CE switch receives a command to add a Layer 3 interface to a VRF, it sets up the appropriate
mapping between the VLAN ID and the policy label (PL) in multi-VRF-CE-related data structures and
adds the VLAN ID and PL to the VLAN database.
When multi-VRF CE is configured, the Layer 3 forwarding table is conceptually partitioned into two
sections:
•
The multi-VRF CE routing section contains the routes from different VPNs.
•
The global routing section contains routes to non-VPN networks, such as the Internet.
VLAN IDs from different VRFs are mapped into different policy labels, which are used to distinguish
the VRFs during processing. If no route is found in the multi-VRF CE section of the Layer 3 forwarding
table, the global routing section is used to determine the forwarding path. For each new VPN route
learned, the Layer 3 setup function retrieves the policy label by using the VLAN ID of the ingress port
and inserts the policy label and new route to the multi-VRF CE routing section. If the packet is received
from a routed port, the port internal VLAN ID number is used; if the packet is received from an SVI, the
VLAN number is used.
VPN 1
VPN 2
VPN 1
VPN 2
CE
Catalyst
6000
Catalyst 3550
switch
Catalyst 3550
switch
Catalyst
6000
PE
PE
Service
provider
CE
CE = Customer edge device
PE = Provider edge router
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