3Com 3C13612, Command Reference Manual

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3Com Router Command Reference Guide — V1.00
View
Tunnel interface view
Parameter
None
Description
Using the gre sequence-datagrams command, you can. configure sequence number
synchronization of datagram on tunnel interface. Using the undo gre
sequence-datagrams command, you can disable sequence number synchronization.
By default, Tunnel interface datagram does not use sequence number
synchronization.
RFC 1701 provides that: if sequence-datagram in the GRE header is set, then the
receiver and sender will undergo sequence number synchronization. Only
synchronous packets will be further processed, otherwise the packet will be
discarded.
The tunnel sequence number provides unreliable but orderly packets. The receiver
makes sequence numbers for the packets received locally and de-capsulated
successfully (the sequence number can be any integer, ranging from 0 to 2
32
–1, with
that of the first packet being 0). After the tunnel is set up, ,the sequence numbers will
be counted in an accumulative and cyclic manner. If the receiver receives a packet
whose sequence number is less than or equal to the sequence number of the last
packet, this packet is deemed to be an illegal packet. If a packet out of sequence is
received, it will be discarded automatically.
Only when gre sequence-datagrams or undo gre sequence-datagrams is set at
both ends of the tunnel can the tunnel be set up.
For related commands, see interface tunnel .
Example
# Set up a tunnel between RouterA and RouterB, whose interfaces are tunnel0 and
tunnel1, respectively. It is required to enable the check of packet sequence number.
[RouterA-Tunnel0] gre sequence-datagrams
[RouterB-Tunnel1] gre sequence-datagrams
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