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FTOS Configuration Guide for the C-Series - Force10 Networks

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The DR is elected using hello messages. Each PIM router learns about its neighbors by periodically<br />

sending a hello message out of each PIM-enabled interface. Hello messages contain <strong>the</strong> IP address of <strong>the</strong><br />

interface out of which it is sent and a DR priority value. The router with <strong>the</strong> greatest priority value is <strong>the</strong><br />

DR. If <strong>the</strong> priority value is <strong>the</strong> same <strong>for</strong> two routers, <strong>the</strong>n <strong>the</strong> router with <strong>the</strong> greatest IP address is <strong>the</strong> DR.<br />

By default <strong>the</strong> DR priority value is 192, so <strong>the</strong> IP address determines <strong>the</strong> DR.<br />

• Assign a DR priority value using <strong>the</strong> command ip pim dr-priority priority-value from INTERFACE<br />

mode.<br />

• Change <strong>the</strong> interval at which a router sends hello messages using <strong>the</strong> command ip pim query-interval<br />

seconds from INTERFACE mode.<br />

• Display <strong>the</strong> current value of <strong>the</strong>se parameter using <strong>the</strong> command show ip pim interface EXEC<br />

Privilege mode.<br />

Creating Multicast Boundries and Domains<br />

A PIM domain is a contiguous set of routers that all implement PIM and are configured to operate within a<br />

common boundary defined by PIM Multicast Border Routers (PMBRs). PMBRs connect each PIM<br />

domain to <strong>the</strong> rest of <strong>the</strong> internet.<br />

Create multicast boundries and domains by filtering inbound and outbound Bootstrap Router (BSR)<br />

messages per interface, use <strong>the</strong> ip pim bsr-border command. This command is applied to <strong>the</strong> subsequent<br />

inbound and outbound updates. Already existing BSR advertisements are removed by timeout.<br />

Remove candidate RP advertisements using <strong>the</strong> clear ip pim rp-mapping command.<br />

PIM-SM Graceful Restart<br />

PIM-SM Graceful Restart is supported only on plat<strong>for</strong>m e<br />

When a PIM neighbor restarts and <strong>the</strong> livelness timer <strong>for</strong> that neighbor expires, <strong>the</strong> join/prune states<br />

received from <strong>the</strong> neighbor expire, and <strong>the</strong> corresponding interfaces are removed from <strong>the</strong> outgoing list of<br />

multicast entries. The effect of this is that active multicast sessions are brought down.<br />

<strong>FTOS</strong> supports PIM-SM graceful restart based on <strong>the</strong> GenID. Per RFC 4601, hello messages should<br />

contain a Generation_Identifier option, which contains a randomly generated value (GenID) that is<br />

regenerated each time PIM <strong>for</strong>warding is started or restarted on <strong>the</strong> interface, including when <strong>the</strong> router<br />

restarts. When a router receives from a neighbor a hello message with a new GenID, any old hello<br />

in<strong>for</strong>mation about that neighbor should be discarded and superseded by <strong>the</strong> in<strong>for</strong>mation from <strong>the</strong> new hello<br />

message.<br />

<strong>FTOS</strong> supports graceful restart based on <strong>the</strong> GenID. An <strong>Force10</strong> PIM router announces its graceful restart<br />

capability to its neighbors upfront as an option in its hello messages.<br />

632 PIM Sparse Mode

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