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Predefined user roles
network-admin
Usage guidelines
HDLC can transport the network layer protocols, such as IP and IPv6.
Examples
# Enable HDLC encapsulation on interface Serial 2/1/0.
<Sysname> system-view
[Sysname] interface serial 2/1/0
[Sysname-Serial2/1/0] link-protocol hdlc
timer-hold
Use timer-hold to set the keepalive interval.
Use undo timer-hold to restore the default.
Syntax
timer-hold seconds
undo timer-hold
Default
The keepalive interval is 10 seconds.
Views
POS interface view
Serial interface view
Predefined user roles
network-admin
Parameters
seconds: Specifies the keepalive interval, in the range 0 to 32767 seconds.
Usage guidelines
An HDLC-enabled interface can regularly check link status by sending keepalives to the peer at the
keepalive interval at the link layer. A keepalive carries the local sender sequence number and the
last received sequence number of the peer.
After sending a keepalive, an interface increments the sender sequence number by 1 in the next
keepalive when the following conditions exist:
• The interface receives a response within the keepalive interval.
• The response carries the sender sequence number in the sent keepalive.
After sending a keepalive, if the interface does not receive a response within the keepalive interval, it
resends the keepalive with an un changed sequence number. When the keepalive retry limit is
reached, the interface considers the link faulty and reports a link layer down event.
Link status check is disabled if you set the keepalive interval to 0.
As a best practice, set the same keepalive interval for the two ends of a link.
If the network has a long delay or is experiencing congestion, you can increase the keepalive interval
to prevent the link from being closed.
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