On S series switches, why cannot inter-area OSPF route summarization take effect

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Question: Why cannot inter-area OSPF route summarization take effect?

Answer: As defined in RFC 2328, when an ABR summarizes inter-area routes, it directly generates a Type 3 LSA regardless of the configured range value. When the ABR summarizes intra-area routes, it generates a Type 3 LSA based on the configured range value.
However, route summarization can cause more LSAs being transmitted into the backbone area, making the network unstable.

Other related questions:
Why cannot OSPF inter-area route summarization take effect
According to RFC 2328, the inter-area Type-3 link-state advertisements (LSAs) generated by an Area Border Router (ABR) are directly processed into corresponding Type-3 LSAs regardless of the configured range. Summarization configuration is considered only in the case of intra-area routes. Such route aggregation, even if achieved, causes more LSAs to be advertised to the backbone area, making the network unstable.

Why static routes imported to OSPF on an S series switch fail to take effect
Question: Why do static routes imported to OSPF fail to take effect? Answer: If a static route imported to OSPF has a lower precedence than other routes, OSPF does not advertise this static route.

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.

Why do static routes imported to OSPF fail to take effect
If a static route imported to OSPF has a lower preference than other routes, OSPF does not advertise this static route.

Why do some routing policies not take effect for a routing protocol on S series switches
When a routing policy contains the routing attribute modification action, the routing policy does not take effect because the routes advertised by the routing protocol cannot carry the attribute. For example, a routing policy is configured to modify the next-hop attribute of OSPF external routes, the routing policy does not take effect because DD packets used to advertise routes do not carry the next-hop attribute. Some routing policies only take effect for certain protocols. For example, the policy where community attributes are matched can only be applied to BGP. In addition, the BGP protocol runs based on point-to-point neighbor relationships; therefore, some policies can be used only on a peer device.

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