H3C MSR Series Command Reference Manual page 73

Predefined user roles
network-admin
Parameters
seconds: Link status polling interval (in seconds), in the range 0 to 32767.
Usage guidelines
HDLC can regularly check link status. If an interface uses HDLC as the link layer protocol, the link layer
sends keepalive packets to the peer at an interval specified by the timer-hold command. A keepalive
packet carries the local sending sequence number and the previous sending sequence number of the
peer. After an interface receives a keepalive packet that carries its previous sending sequence number,
it increments the previous sending sequence number by 1 in the keepalive packet to be sent next time.
Otherwise, it uses the previous sending sequence number. If an interface fails to receive keepalive
packets carrying its previous sending sequence number within five polling intervals, it considers the link
faulty and reports a link layer down event.
Setting the link status polling interval to 0 disables link status check.
H3C recommends that you set the same interval for the two ends of a link.
If the network has a long delay or is experiencing congestion, you can increase the polling interval to
prevent the link from being closed.
Examples
# Set the link status polling interval to 100 seconds on interface Serial 2/0.
<Sysname> system-view
[Sysname] interface serial 2/0
[Sysname-serial2/0] timer-hold 100
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