Changing The Shortest Path Tree (Spt) Threshold - Dell PowerConnect B-RX Configuration Manual

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Changing the Shortest Path Tree (SPT) threshold

BigIron RX(config-pim-router)#show ip pim sparse
Global PIM Sparse Mode Settings
Hello interval : 30 Neighbor timeout : 105
Bootstrap Msg interval: 60 Candidate-RP Advertisement interval: 60
Join/Prune interval : 60 SPT Threshold : 1
Inactivity interval : 180 SSM Enabled : No
Hardware Drop Enabled : Yes
Route Selection : mc-non-default uc-non-default mc-default uc-default
---------+----------------+----+---+----------------------+------+-------------+
Interface|Local
---------+----------------+----+---+----------------------+------+-------------+
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.
•
•
By default, the device switches from the RP to the SPT after receiving the first packet for a given
PIM Sparse group. The BigIron RX maintains a separate counter for each PIM Sparse source-group
pair.
After the BigIron RX receives a packet for a given source-group pair, the BigIron RX starts a PIM
data timer for that source-group pair. If the BigIron RX 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's recommendation, the timer is 210
seconds and is not configurable. The counter is reset to zero each time the BigIron RX receives a
packet for the source-group pair.
You can change the number of packets that the BigIron RX sends using the RP before switching to
using the SPT.
To change the number of packets the BigIron RX sends using the RP before switching to the SPT,
enter commands such as the following.
BigIron RX(config)# router pim
BigIron RX(config-pim-router)# spt-threshold 1000
Syntax: [no] spt-threshold infinity | <num>
606
|Address
v12 100.4.8.2
v13 100.16.8.2
v124 124.0.0.1
v125 125.0.0.1
v126 126.0.0.1
v127 127.0.0.1
l1 1.0.8.1
Path through the RP – This is the path the BigIron RX 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 BigIron RX
to the receiver.
Shortest Path – Each PIM Sparse router 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
BigIron RX itself as the root of the tree. The first time a BigIron RX is configured as a PIM router
and receives a packet for a PIM receiver, the BigIron RX sends the packet to the RP for the
group. The BigIron RX also calculates the SPT from itself to the receiver. The next time the
BigIron RX receives a PIM Sparse packet for the receiver, the BigIron RX sends the packet
toward the receiver using the shortest route, which may not pass through the RP.
|Mode|Ver| Designated Router
| | |Address
SM V2 Itself
SM V2 Itself
SM V2 Itself
SM V2 Itself
SM V2 Itself
SM V2 Itself
SM V2 Itself
|TTL |Multicast
Port |Thresh|Boundary
1 None
1 None
1 None
1 None
1 None
1 None
1 None
BigIron RX Series Configuration Guide
53-1001986-01
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