HP 6125XLG R2306-HP 6125XLG Blade Switch IP Multicast Configuration Guide - Page 86

To guard against PIM message attacks, you can configure a legal source address range for hello messages on interfaces of routers to ensure the correct PIM neighboring relationships. To configure a hello message filter: Step 1. Enter system view. 2. Enter interface view. 3. Configure a hello message filter. Command system-view interface interface-type interface-number pim neighbor-policy acl-number Remarks N/A N/A By default, no hello message filter exists. If a PIM neighbor's hello messages cannot pass the filter, the neighbor is automatically removed when its maximum number of hello attempts is reached. Configuring PIM hello message options In either a PIM-DM domain or a PIM-SM domain, hello messages exchanged among routers contain the following configurable options: • DR_Priority (for PIM-SM only)-Priority for DR election. The device with the highest priority wins the DR election. You can configure this option for all the routers in a shared-media LAN that directly connects to the multicast source or the receivers. • Holdtime-PIM neighbor lifetime. If a router does not receive a hello message from a neighbor when the neighbor lifetime expires, it regards the neighbor failed or unreachable. • LAN_Prune_Delay-Delay of forwarding prune messages on a shared-media LAN. This option consists of LAN delay (namely, prune message delay), override interval, and neighbor tracking support (namely, the capability to disable join message suppression). The prune message delay defines the delay time for a router to forward a received prune message to the upstream routers. The override interval defines a period for a downstream router to override a prune message. If the prune message delay or override interval on different PIM routers on a shared-media LAN are different, the largest value takes effect. A router does not immediately prune an interface after it receives a prune message from the interface. Instead, it starts a timer (the prune message delay plus the override interval). If interface receives a join message before the override interval expires, the router does not prune the interface. Otherwise, the router prunes the interface when the timer (the prune message delay plus the override interval) expires. You can enable the neighbor tracking function (or disable the join message suppression function) on an upstream router to track the states of the downstream nodes that have sent the join message and the joined state holdtime timer has not expired. If you want to enable the neighbor tracking function, you must enable it on all PIM routers on a shared-media LAN. Otherwise, the upstream router cannot track join messages from every downstream routers. • Generation ID-A router generates a generation ID for hello messages when an interface is enabled with PIM. The generation ID is a random value, but only changes when the status of the router changes. If a PIM router finds that the generation ID in a hello message from the upstream router has changed, it assumes that the status of the upstream router has changed. In this case, it sends a join message to the upstream router for status update. You can configure an interface to 79