Brocade Multi-Service IronWare Multicast Configuration Guide (Supporting R05.6.00) - Manual (Page 61)

Multi-Service IronWare Multicast Configuration Guide 49
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PIM Sparse
1
---------+---------------+----+---+---------------------+---+---------+-------+------+---------+
Interface|Local |Ver |St | Designated Router |TTL|Multicast| VRF | DR | Override
|Address | | |Address Port|Thr|Boundary | | Prio | Interval
---------+---------------+----+---+---------------------+---+---------+-------+------+---------+
v3 3.1.1.2 SMv2 Ena Itself 1 None default 1 3000ms
v4 4.1.1.2 SMv2 Ena Itself 1 None default 1 3000ms
v10 10.1.1.1 SMv2 Ena Itself 1 None default 1 3000ms
v12 12.1.1.1 SMv2 Ena Itself 1 None default 1 3000ms
v33 33.1.1.1 SMv2 Ena 33.1.1.2 1/14 1 None default 1 3000ms
l1 1.1.1.3 SMv2 Ena Itself 1 None default 1 3000ms
Total Number of Interfaces : 6
In this example, the route precedence selection is multicast non-default, then unicast non-default,
then multicast default, and then unicast default.
NOTE
In Brocade implemention, the LHR directly sends the PIM joins towards RP instead of DR in a
broadcast network. You are advised to enable PIM in all the routers in the broadcast domain
because the Unicast RTM currently only stores the BEST METRIC path towards a particular IP
address and that is all that Multicast has access to when it polls the RTM. If the next hop neighbor
for that path is NOT PIM enabled, then PIM will not know where to pick up the next available path
(since the RTM doesnt hold it).
Changing the Shortest Path Tree (SPT) threshold
In a typical PIM Sparse domain, there may be two or more paths from a DR (designated router) for
a multicast source to a PIM group receiver:
• Path through the RP – This is the path the device uses the first time it receives traffic for a PIM
group. However, the path through the RP may not be the shortest path from the device to the
receiver.
• Shortest Path – Each PIM Sparse device that is a DR for a multicast source calculates a
shortest path tree (SPT) to all the PIM Sparse group receivers within the domain, with the
device itself as the root of the tree. The first time a device configured as a PIM router receives
a packet for a PIM receiver, the device sends the packet to the RP for the group. The device
also calculates the SPT from itself to the receiver. The next time the device receives a PIM
Sparse packet for the receiver, the device sends the packet toward the receiver using the
shortest route, which may not pass through the RP.
By default, the device switches from the RP to the SPT after receiving the first packet for a given
PIM Sparse group. The device maintains a separate counter for each PIM Sparse source-group pair.
After the device receives a packet for a given source-group pair, it starts a PIM data timer for that
source-group pair. If the device does not receive another packet for the source-group pair before
the timer expires, it reverts to using the RP for the next packet received for the source-group pair. In
accordance with the PIM Sparse RFC recommendation, the timer is 210 seconds and is not
configurable. The counter is reset to zero each time the device receives a packet for the
source-group pair.
You can change the number of packets that the device sends using the RP before switching to
using the SPT by entering commands such as the following.
Brocade(config)# router pim
Brocade(config-pim-router)# spt-threshold 1000
Syntax: [no] spt-threshold infinity | num