Huawei v200r001 user manual Monitoring and Maintenance of GRE, Show interface tunnel tunnel-number

User Manual - Configuration Guide (Volume 3)	Chapter 3
Versatile Routing Platform	Configuration of GRE

compares it with the check sum in the message. If the two check sums are identical, the message will be further processed, or it will be discarded.

If only one end of the tunnel is configured to check with the check sum, the message will not be checked with check sum. Only when both ends of the tunnel are configured to check with the check sum, can the message be checked with the check sum.

Perform the following task in tunnel interface configuration mode.

Table VPN-3-7Set tunnel interface to check with check sum

Operation	Command
Set tunnel interface to check with check sum.	tunnel checksum
Disable tunnel interface to check with check sum.	no tunnel checksum

Disable tunnel interface to check with check sum by default.

3.2.9 Setting Tunnel Interface to Synchronize Datagram Serial Number

It is stipulated in RFC 1701 that: if “sequence-datagram” in GRE header is set, both receiving side and transmitting side will synchronize serial numbers. The synchronized message should be further processed, or it is discarded.

With the serial numbers, the message is unreliable but in order. The receiving end establishes serial numbers for the message which is received by local end and successfully de-encapsulated (The serial numbers are integers between 0 and 232–1 and the serial number of the first packet is 0). After the channel is established, the serial numbers will be accumulated and cyclically counted. If the receiving end receives a message whose serial number is less than or equal to that of the message received last time, the packet will be considered as illegal. If the receiving end receives an orderless message, the packet will be automatically discarded.

Only when the synchronization mechanism to set/disable serial numbers is established at both ends of the tunnel, can the channel be established.

Perform the following task in tunnel interface configuration mode.

Table VPN-3-8Set the tunnel to synchronize datagram serial numbers

Operation	Command
Set tunnel interface to synchronize serial numbers.	tunnel sequence-datagrams
Disable tunnel interface to synchronize serial numbers.	no tunnel sequence-datagrams

Disable tunnel interface to synchronize datagram serial numbers by default.

3.3 Monitoring and Maintenance of GRE

Perform the following task in privileged user mode.

Table VPN-3-9Monitoring and maintenance of GRE

Operation	Command
Show the working status of tunnel interface.	show interface tunnel [tunnel-number]

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