Configuration Guide User guide

FastIron Configuration Guide 1529
53-1002494-02
PIM Dense
Due to the Highest IP RFP feature, the selection of the shortest path back to the source is based on
which Reverse Path Forwarding (RPF) neighbor in the IP routing table has the highest IP address, if
the cost of the routes are the same. For example, in the table above, Gateway 137.80.129.1 will be
chosen as the shortest path to the source because it is the RPF neighbor with the highest IP
address.
When choosing the RPF, the router first checks the Multicast Routing Table. If the table is not
available, it chooses an RPF from the IP Routing Table. Multicast route is configured using the ip
mroute command.
The Highest IP RFP feature is enabled by default.
Failover time in a multi-path topology
When a port in a multi-path topology fails, and the failed port is the input port of the downstream
router, a new path is re-established within a few seconds, depending on the routing protocol being
used.
No configuration is required for this feature.
Modifying the TTL
The time to live (TTL) defines the minimum value required in a packet for it to be forwarded out of
the interface.
For example, if the TTL for an interface is set at 10, it means that only those packets with a TTL
value of 10 or more will be forwarded. Likewise, if an interface is configured with a TTL Threshold
value of 1, all packets received on that interface will be forwarded. Possible TTL values are 1 to 31.
The default TTL value is 1.
Configuration notes for modifying the TTL
• If the TTL for an interface is greater than 1, PIM packets received on the interface are always
forwarded in software because each packet TTL must be examined. Therefore, Brocade does
not recommend modifying the TTL under normal operating conditions.
• Multicast packets with a TTL value of 1 are switched within the same VLAN. These packets
cannot be routed between different VLANs.
Total number of IP routes: 19
B:BGP D:Connected R:RIP S:Static O:OSPF *:Candidate default
Destination NetMask Gateway Port Cost Type
..
9 172.17.41.4 255.255.255.252*137.80.127.3 v11 2 O
172.17.41.4 255.255.255.252 137.80.126.3 v10 2 O
172.17.41.4 255.255.255.252 137.80.129.1 v13 2 O
172.17.41.4 255.255.255.252 137.80.128.3 v12 2 O
10 172.17.41.8 255.255.255.252 0.0.0.0 1/2 1 D