Brocade Communications Systems IPMC5000PEF manual Failover time in a multi-path topology

Failover time in a multi-path topology

Modifying graft retransmit timer

The graft retransmit timer defines the interval between the transmission of graft messages.

A graft message is sent by a device to cancel a prune state. When a device receives a graft message, the device responds with a Graft Ack (acknowledge) message. If this Graft Ack message is lost, the device that sent the graft message will resend it.

To change the graft retransmit timer from the default of 180 to 90 seconds, enter the following.

Device(config)# router pim

Device(config-pim-router)# graft-retransmit-timer 90

Syntax: [no] graft-retransmit-timer seconds

The default is 180 seconds. The range is from 60 to 3600 seconds.

Modifying inactivity timer

The device deletes a forwarding entry if the entry is not used to send multicast packets. The PIM inactivity timer defines how long a forwarding entry can remain unused before the device deletes it.

To apply a PIM inactivity timer of 90 seconds to all PIM interfaces, enter the following.

Device(config)# router pim

Device(config-pim-router)# inactivity-timer 90

Syntax: [no] inactivity-timer seconds

The default is 180 seconds. The range is from 60 to 3600 seconds.

Selection of shortest path back to source

By default, when a multicast packet is received on a PIM-capable interface in a multi-path topology, the interface checks its IP routing table to determine the shortest path back to the source. If the alternate paths have the same cost, the first alternate path in the table is picked as the path back to the source. For example, in the following example, the first four routes have the same cost back to the source. However, 137.80.127.3 is chosen as the path to the source since it is the first one on the list. The device rejects traffic from any port other than Port V11 on which 137.80.127.3 resides

Total number of IP routes: 19

Type Codes - B:BGP D:Connected I:ISIS S:Static R:RIP O:OSPF Cost - Dist/Metric

Destination	Gateway	Port	Cost	Type
..	137.80.127.3	v11	2	O
172.17.41.4
172.17.41.4	137.80.126.3	v10	2	O
172.17.41.4	137.80.129.1	v13	2	O
172.17.41.4	137.80.128.3	v12	2	O
172.17.41.8	0.0.0.0	1/2	1	D

Failover time in a multi-path topology

When a port in a multi-path topology fails, multicast devices, depending on the routing protocol being used, take a few seconds to establish a new path, if the failed port is the input port of the downstream device.

88	FastIron Ethernet Switch IP Multicast Configuration Guide
	53-1003085-02