How to solve the problem if the length of a packet encapsulated with the VXLAN header exceeds the MTU of an underlay network device


A CE series switch functions as the VXLAN gateway and adds VXLAN headers to data packets that enter the VXLAN tunnel. After VXLAN encapsulation, the encapsulated packets have 54 bytes more than original data packets. The length of encapsulated packets may exceed the MTU of the underlay network device. As a result, packets are discarded by the device. You can use one of the following methods or a combination of them based on the functions supported by the underlay network device: 1. Configure the maximum length of Jumbo frames allowed by the underlay network device so that the maximum length of Jumbo frames is larger than the length of VXLAN packets. 2. Configure the MTU of the underlay network device so that the MTU is larger than the length of VXLAN packets. 3. Deploy the VXLAN gateway on the device such as the CE6880EI that supports packet fragmentation and reassembly. The device then fragments and reassembles VXLAN packets so that VXLAN packets can be forwarded on the underlay network.

Other related questions:
How do I solve the DHCP configuration loss problem after device restart

After the device restarts, there is a low probability that the DHCP configuration is lost.

Auto-Config is enabled by default. About two and a half minutes after the device restarts, the Auto-Config module checks whether the configuration file exists and determine whether the Auto-Config process is executed. If the save command is used at this time, files conflict. As a result, the Auto-Config module determines that the configuration file does not exist, and incorrectly executes the Auto-Config process. In this case, information about option fields or intermediate file required for executing the Auto-Config process is not configured on the DHCP server. Consequently, the Auto-Config process is suspended, and the DHCP configuration (including the configuration during configuration recovery and the Auto-Config process) is deleted.

After the device restarts, run the undo autoconfig enable command in the system view to disable Auto-Config.

Differences between the MTU and frame length
Maximum transmission unit (MTU) refers to the length of a Layer 3 packet, that is, the length of an IP data packet. Frame length refers to the length of a Layer 2 Ethernet frame. The right figure uses a standard Ethernet frame to compare the MTU and frame length.

How to solve the problem that couldn't open U1900 webpage?
1.Some U1900 gateway versions support enabling http protocal by checking whether there is "config http switch on" command displayed in CLI printouts when type command "ls http". If exists,test after executing this command。 2.Else,make sure whether U1900 V100R001C01 does't support. 3.Reload webfile. a) Open TFTP service on PC, and put version files to TFTP server directory. b) Run command :config system hostip,the ip is TFTP server address. c) config download file webfile mode tftp d) config download file webrootcrt mode tftp e) config download file websrvcrt mode tftp f) config download file websrvkey mode tftp

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