Reason why the undo icmp host-unreachable send command does not take effect on S series switches

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On S series switches (except the S1700), the undo icmp host-unreachable send command does not take effect for private network routes. Switches running V100R006 and earlier versions do not support this command, and switches running V200R001 and later versions support this command.

Other related questions:
IPSG does not take effect on an S series switch. What are the possible causes
If IPSG does not take effect on an S series switch (except the S1700), possible causes include the following: 1. A binding entry is incorrect. a. A static binding table is created using the user-bind static command. If the binding entry of a valid host is not in the binding table, add the host's binding entry to the binding table. If the host's entry exists in the binding table, check whether the MAC address in the entry is the same as the host's MAC address. If the network card of the host is replaced, the MAC address in the entry may not be updated. Check whether the host's entry contains VLAN information. Only when the interface connected to this host has been added to the correct VLAN, the switch allows the packets from the host to pass. b. A dynamic binding table is generated only when DHCP snooping is enabled, the interface connected to the DHCP server is configured as a trusted interface, and then the PC obtains a new IP address. 2. IPSG is not enabled in the specified interface or VLAN view. 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 VLANs with IPSG disabled. 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. 3. IPSG is enabled in the VLAN to which the uplink interface belongs. IPSG is enabled on the user-side interface, namely, the downlink interface. If IPSG is enabled on the uplink interface, the packets returned by the gateway may be discarded. As a result, user service is interrupted. Solution: Disable IPSG in the VLAN to which the uplink interface belongs. 4. DHCP snooping is disabled or a DHCP snooping trusted interface is configured on the uplink interface or in the VLAN to which the uplink interface belongs. If DHCP snooping if disabled on an interface using the dhcp snooping disable command, or if a DHCP snooping trusted interface is configured on the interface using the dhcp snooping trusted command, the IPSG function on the interface or in the VLAN to which the interface belongs does not take effect. 5. Hardware ACL resources are insufficient. The hardware ACL resources are used 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 cause is that hardware ACL resources are insufficient. 6. A QoS traffic policy conflicts with IPSG. 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. In this situation, you need to modify service configurations.

The reason of S series switches TUNNEL port MTU does not take effect
S series switches (except S1700) MTU of the TUNNEL port is valid only for the uplink control plane and the packets sent from the control plane. The MTU does not take effect for the data packets directly forwarded at the hardware level. The hardware level MTU need to configure the MTU value of the physical interface.

Why does the egress policy configured on an RR not take effect on S series switches
Q: Why does the egress policy configured on an RR not take effect? A: The route reflection attribute of the reflector is the route attribute determined by the ingress policy and is not affected by either the egress policy or the peer { group-name | ipv4-address | ipv6-address } next-hop-local command.

Why do configuration commands not take effect on CE series switches
After configuring commands in two-stage mode on CE series switches, you need to run the commit command to make the configurations take effect. In the two-stage mode, the system configuration process is divided into two stages: Stage 1: Enter a configuration command and edit the configuration. Stage 2: Run the commit command to submit the configuration so that the new configuration takes effect in the current system. In V100R003 and later versions, if a user modifies a configuration in two-stage mode but does not submit the configuration, the system prompt changes from ~ to *, reminding the user that the configuration has not been submitted. The system prompt will change back to ~ after the user runs the commit command. Uncommitted configurations will not be saved in the configuration file.

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