Enabling The Distributed Periodic Packet Management Process For Vrrp - Juniper EX9200 Features Manual

High Availability Feature Guide for EX9200 Switches
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Enabling the Distributed Periodic Packet Management Process for VRRP

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Understanding VRRP on page 119
Typically, VRRP advertisements are sent by the VRRP process (vrrpd) on the master
VRRP router at regular intervals to let other members of the group know that the VRRP
master router is operational.
When the vrrpd process is busy and does not send VRRP advertisements, the backup
VRRP routers might assume that the master router is down and take over as the master
router, causing unnecessary flaps. This takeover might occur even though the original
master router is still active and available and might resume sending advertisements after
the traffic has decreased. To address this problem and to reduce the load on the vrrpd
process, Junos OS uses the periodic packet management process (ppmd) to send VRRP
advertisements on behalf of the vrrpd process. However, you can further delegate the
job of sending VRRP advertisements to the distributed ppmd process that resides on the
Packet Forwarding Engine.
The ability to delegate the sending of VRRP advertisements to the distributed ppmd
process ensures that the VRRP advertisements are sent even when the ppmd
process—which is now responsible for sending VRRP advertisements—is busy. Such
delegation prevents the possibility of false alarms when the ppmd process is busy. The
ability to delegate the sending of VRRP advertisements to distributed ppmd also adds
to scalability because the load is shared across multiple ppmd instances and is not
concentrated on any single unit.
NOTE: CPU-intensive VRRP advertisements, such as advertisements with
MD5 authentication, continue to be processed by the VRRP process on the
Routing Engine even when distributed ppmd is enabled.
NOTE: VRRP is supported by graceful Routing Engine switchover only in the
case that PPM delegation is enabled (the default).
NOTE: Aggregated Ethernet and integrated routing and bridging (IRB)
delegation is supported only for MPC line cards.
To configure the distributed ppmd process to send VRRP advertisements, include the
delegate-processing statement at the
[edit protocols vrrp]
delegate-processing;
[edit protocols vrrp] hierarchy level:
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