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.

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 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.

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 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.

Why does IPSG fail to take effect
The possible causes are as follows: --Invalid binding entries A static binding table is created using the user-bind static command. A dynamic binding table is generated only after the DHCP snooping function is enabled. --IPSG not enabled on the specified interface or VLAN After a binding table is generated, the IPSG function must be enabled in the interface or VLAN view using the ip source check user-bind enable command. IPSG takes effect only on the interface or VLAN where it is enabled, and IPSG check is not performed on the interfaces or VALNs without IPSG enabled. Therefore, if IPSG does not take effect on an interface or in a VLAN, the IPSG function may not be enabled on this interface or in this VLAN. --Insufficient hardware ACL resources The hardware ACL resources are shared by IPSG and other services. If the ACL resources are insufficient, IPSG cannot take effect. For example, you can run the display dhcp static user-bind all verbose command to view the IPSG status corresponding to static binding entries. If the value of IPSG Status is ineffective, IPSG of this entry does not take effect. The possible reason is that hardware ACL resources are insufficient. --Conflict between IPSG and QoS traffic policy This situation may only occur in V1R6C05. When a QoS traffic policy conflicts with IPSG, the traffic behavior in the QoS traffic policy takes effect.

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