External routes imported using OSPF on a CE series switch cannot be viewed in the routing table

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This problem is caused by routing loop detection. By default, routing loop detection is enabled on a CE series switch. When OSPF VPN multi-instance is deployed on a Multi-VPN-Instance CE (MCE) device, and DN Bit is set in Type 3, Type 5, or Type 7 LSAs, corresponding routes cannot be calculated and viewed in the routing table because routing loop detection is performed during OSPF route calculation. To address this problem, run the vpn-instance-capability simple command on the MCE device to disable routing loop detection of the OSPF instance.

Other related questions:
Precedence of external routes imported by OSPF on S series switches
When an S series switch runs OSPF, you can run the import-route command in the OSPF process view to import external routes. The routes imported using this method are OSPF ASE routes and default precedence is 150.

Why cannot OSPF on S series switches import BGP routes
Question: Why cannot OSPF import BGP routes? Answer: As defined in RFC 1364, routes learned via IBGP must not be imported into OSPF. That is, OSPF cannot import IBGP routes. PEs can import IBGP routes. Most VPNv4 routing tables contain BGP routes, but the routes cannot be imported into OSPF processes. This is because the vpn-instance-capability simple command is configured in the OSPF processes. After the command is configured, the PE role is disabled on a device and the device acts as an MCE. To enable the PE role on a device, run the undo vpn-instance-capability command.

USG2000 / 5000 Configure OSPF to import external routes
USG2000 & 5000 Configure OSPF to import external routes as follows: 1. Configure the basic parameters of each interface to implement interworking. 2. Configure OSPF on the USG. 3. Configure the OSPF area on the USG and add the Internet segment on the USG to the OSPF area. 4. Configure OSPF to import direct routes on the egress gateway.

Why cannot OSPF import BGP routes
As defined in RFC 1364, OSPF cannot import IBGP routes. Routes learned via IBGP must not be imported into OSPF OSPF, however, can import IBGP routes on a PE. BGP routes exist in a VPNv4 routing table on a device functioning as a PE but cannot be imported to OSPF. This is because the role of the device changes from a PE to an MCE after the vpn-instance-capability simple command in run in the OSPF process. Solution: If the device needs to function as a PE, you need to run the undo vpn-instance-capability command on the device.

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