Juniper JUNOSE SOFTWARE 11.2.X - LINK LAYER CONFIGURATION GUIDE 7-7-2010 Configuration Manual page 307

ppp keepalive
Copyright © 2010, Juniper Networks, Inc.
Use to specify the IPCP netmask option (option 0x90) for each PPP interface. By
default, the IPCP netmask option is disabled on the interface.
The IPCP netmask option is a nonstandard option that enables a peer to request the
netmask associated with the assigned IP address.
The netmask can be specified via RADIUS attribute 9, Framed-Ip-Netmask. If the
netmask is 255.255.255.255, the option is not negotiated. See the radius ignore
framed-ip-netmask command.
You can enable the IPCP netmask option either in a profile or on a static interface.
Example
host1(config-subif)#ppp ipcp netmask
Use the no version to disable the IPCP netmask option on the interface.
See ppp ipcp netmask.
Use to specify the keepalive timeout value.
There are two keepalive modes of operation: high-density mode and low-density mode.
High-density keepalive mode is automatically selected if PPP is layered over ATM,
L2TP, or PPPoE.
Low-density keepalive mode is selected if PPP is layered over HDLC. Keepalive mode
selection is made per interface.
High-density mode—This mode is also known as smart keepalive. When the keepalive
timer expires, the interface first verifies whether any frames were received from the
peer in the prior keepalive timeout interval. If so, the interface does not send an LCP
echo request (keepalive). Keepalive packets are sent only if the peer is silent (that is,
no traffic was received from the peer during the previous keepalive timeout interval).
If both sides are configured with keepalive, receipt of an LCP echo request by one end
suppresses the transmission of an LCP echo request by that end. Smart keepalive is
disabled when the keepalive timeout value is at least 60 seconds, even when in
high-density mode. Smart keepalive is always disabled when in low-density mode.
This mode suppresses transmission of unnecessary LCP echo requests.
For high-density keepalive mode, the range is 30–64800 seconds. The default value
is 30 seconds.
Low-density mode—When the keepalive timer expires, the interface always sends an
LCP echo request, regardless of whether the peer is silent.
For low-density keepalive mode, the range is 1–64800 seconds for POS uplink
interfaces, and 10–64800 seconds for all other HDLC interfaces. The default value for
all interfaces is 30 seconds.
If the keepalive interval is 30 seconds, a failed link is detected between 90 and 120
seconds after failure.
Use ppp keepalive without a value to restore the default, 30 seconds.
Chapter 8: Configuring Point-to-Point Protocol
275