OSPF Sham-Link Support for MPLS VPN
Supported Standards, MIBs, and RFCs
10
Cisco IOS Release 12.2(8)T
Supported Standards, MIBs, and RFCs
Standards
No new or modified standards are supported by this feature.
MIBs
No new or modified MIBs are supported by this feature.
To obtain lists of supported MIBs by platform and Cisco IOS release, and to download MIB modules,
go to the Cisco MIB website on Cisco.com at the following URL:
http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml
RFCs
No new or modified RFCs are supported by this feature.
Prerequisites
Before you can configure a sham-link in an MPLS VPN, you must first enable OSPF as follows:
•Create an OSPF routing process.
•Specify the range of IP addresses to be associated with the routing process.
•Assign area IDs to be associated with the range of IP addresses.
For more information on these OSPF configuration procedures, go to:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fiprrp_r/1rfospf.htm
Configuration Tasks
See the following sections for configuration tasks for the sham-link feature. Each task in the list is
identified as either required or optional.
•Creating a Sham-Link (required)
•Verifying Sham-Link Creation (optional)

Creating a Sham-Link

Before you create a sham-link between PE routers in an MPLS VPN, you must:
•Configure a separate /32 address on the remote PE so that OSPF packetscan be sent over the VPN
backbone to the remote end of the sham-link. The /32 address must meet the following criteria:
–
Belong to a VRF.
–
Not be advertised by OSPF.
–
Be advertised by BGP.
You can use the /32 address for other sham-links.
•Associate the sham-link with an existing OSPF area.