Why the S series switches do not generate backup information for static routes or BGP routes after configuring IP FRRs

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The iterative route does not apply the IP FRR configuration directly, but inherits next-hop route through the backup outbound interface and the backup next hop generated by IP FRR. Static route or BGP route If it is an iterative route and the next hop route does not generate backup information of IP FRR, static route or BGP route does not generate backup information even if it matches IP FRR policy.

Other related questions:
Why cannot the backup information of a static route or a BGP route be generated after IP FRR is configured
IP FRR does not automatically take effect for iterated routes. Instead, an iterated route inherits the backup outbound interface and backup next hop of the route to the next hop that are generated through IP FRR. If the static route or BGP route is an iterated route and the IP FRR backup information of the next hop route is not generated, the backup information cannot be generated although the static route or BGP route matches the IP FRR policy.

On S series switches, how long does it take for BGP routes to expire after the static routes imported by BGP expire
If the static routes imported by an S series switch become invalid, the routes imported in the BGP routing table will be invalidated. The route imported through the network command must be active in the local routing table. Otherwise, it cannot be imported in the BGP routing table.

Why do not S series switches functioning as ASBRs generate equivalent routes
Question: Why do not ASBRs generate equivalent routes? Answer: Two areas are enabled on two S series switches supporting OSPF, for example: Switch A: Area 0: 10.5.5.5 Area 1: 10.4.4.4 Switch B: Area 0: 10.5.5.6 Area 1: 10.4.4.6 Then the switches set up an adjacency relationship. When Switch B imports a route from Switch A, the next-hop address of the route can be 10.5.5.5 or 10.4.4.4. However, only the route through Area 1 with the IP address 10.4.4.4 is displayed on Switch B. This is because when multiple equal-cost routes exist, the route with the largest area ID is preferentially selected.

How to configure BGP to import routes for S series switches
Background BGP itself cannot discover routes. Therefore, it needs to import other protocol routes, such as IGP routes, to the BGP routing table. In this manner, these imported routes can be transmitted within an AS or between ASs. BGP imports routes in either of the following ways: In import mode, BGP imports routes according to protocol types, such as RIP routes, OSPF routes, and IS-IS routes. To ensure validity of imported IGP routes, BGP can also import static routes and direct routes in import mode. In network mode, BGP imports routes in an IP routing table one by one, making it more precise than the import mode. Procedure Import mode: [HUAWEI] bgp 100 [HUAWEI-bgp] ipv4-family unicast //The IPv4 address family view is displayed. You can also enter other views as required. [HUAWEI-bgp-af-ipv4] import-rout static //Importing static routes is taken as an example. Importing routes of other protocols is similar. (Optional) Run the default-route import command to allow BGP to import the default route that already exists in the local IP routing table. By default, BGP does not add default routes to the BGP routing table. Network mode: [HUAWEI] bgp 100 [HUAWEI-bgp] ipv4-family unicast //The IPv4 address family view is displayed. You can also enter other views as required. [HUAWEI-bgp-af-ipv4] network 192.168.100.0 24 //Advertise routes to network segment 192.168.100.0 24. Precaution The network command is used to advertise exactly matched routes. That is, the routes whose destination addresses and prefix lengths exactly match the entries in the local routing table. If the network mask is not specified, routes are exactly matched according to the natural network segment. When using the undo network command to clear the existing configuration, you need to specify the correct mask.

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.

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