Services Are Abnormal Because the Upstream Interface Is Not Configured as a Trusted Interface

Procedure

1. Check whether the upstream interface belongs to the VLAN with IPSG enabled.

   If the upstream interface belongs to the VLAN, configure this interface as a trusted interface; otherwise, the return packets are discarded because they do not match the binding entries. As a result, user services are interrupted.

   In Figure 1, Host_1 and Host_2 belong to VLAN 10. IF3 allows the packets of VLAN 10 to pass. The static binding entries are configured on the switch for Host_1 and Host_2, and IPSG is enabled in VLAN 10. The hosts can communicate with each other, but cannot access the Internet. Host_1 is used as an example here to describe the fault symptom:

   • Host_1 sends a packet to the Internet. When the packet reaches IF1 of the switch, the switch detects that the packet matches a binding entry, and forwards it.
   • A packet is sent from the Internet to Host_1. When the packet reaches IF3, which belongs to VLAN 10, the switch detects that the packet does not match any binding entry, and discards the packet.
   Figure 1 Services are abnormal because the upstream interface is not configured as a trusted interface
   
   

2. Perform the following operations:
   1. Run the system-view command to enter the system view.
   2. Run the dhcp enable command to enable DHCP globally.
   3. Run the dhcp snooping enable command to enable DHCP snooping globally.
   4. Run the interface interface-type interface-number command to enter the IF3 interface view.
   5. Run the dhcp snooping trusted command to configure IF3 as a trusted interface.