Terminating Stale Pppoa Subscribers And Restarting Lcp Negotiations - Juniper JUNOSE SOFTWARE FOR E SERIES 11.3.X - LINK LAYER CONFIGURATION GUIDE 2010-10-13 Configuration Manual

JunosE 11.3.x Link Layer Configuration Guide

Terminating Stale PPPoA Subscribers and Restarting LCP Negotiations

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In configurations of dynamic IP over dynamic PPP over a static ATM 1483 subinterface,
as shown in Figure 47 on page 526, any of the following conditions might cause the static
ATM 1483 subinterface to transition to a dormant state as the result of an ungraceful
subscriber logout:
Rebooting the router
Rebooting a line module
Transitioning the physical (for example, SONET) interface, ATM major interface, or
ATM AAL5 interface from up to down to up again
Transitioning the ATM 1483 subinterface or the ATM PVC from up to down to up again
Any other lowerLayerDown operational status condition that affects the dynamic PPP
interface; a lowerLayerDown status indicates that a lower-layer interface below the
dynamic PPP interface is down
When the ATM 1483 subinterface transitions to a dormant state as a result of any of
these conditions, the router tears down the dynamic PPP interface column. The dynamic
PPP interface is unable to send an LCP terminate request to its peer because its own
lower-layer interface is down. This action causes a loss of connectivity between the
router and the PPPoA customer premises equipment (CPE). If the CPE supports the PPP
keepalive feature, it can detect the loss of connectivity and restart Link Control Protocol
(LCP) negotiations in order to initiate a new connection. However, if the CPE does not
support PPP keepalive, it cannot detect that the connection is down, and continues to
send PPP data packets to the router.
On receipt of an IPv4-over-PPP data packet or an IPv6-over-PPP data packet from the
CPE when the ATM 1483 subinterface transitions to a dormant state, the router sends
an LCP terminate request packet to the CPE. Receipt of the LCP terminate request packet
causes the CPE to restart LCP negotiations in order to initiate a new connection. After
the CPE restarts LCP negotiations, the router recreates the dynamic PPP and IP
upper-layer interfaces above the static ATM 1483 subinterface. This behavior is always
in effect on the router and does not require CLI or SNMP configuration.
Sending an LCP terminate request packet in response to receipt of an IPv4-over-PPP
data packet or an IPv6-over-PPP data packet from a PPPoA CPE device offers the
following benefits:
For CPEs that support PPP keepalive, receipt of an LCP terminate request packet from
the router restarts the LCP negotiations more quickly.
For CPEs that do not support PPP keepalive, receipt of an LCP terminate request packet
from the router enables the CPE to detect the connection termination and restart LCP
negotiations in response.
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