KB.15.15

[no]vlanvidip pim

Enables multicast routing on the VLAN interface to which the CLI is currently set.

The no form disables PIM on the VLAN.

Default: Disabled

Specifying the IP address to use as the source address for PIM protocol packets

outbound on the VLAN

Syntax:

[no]ip pim-dense [ ip-addr any | sourceip-address ]

[no]vlan[vid]ip pim-dense [ ip-addr | any |

sourceip-address ]

In networks using multinetted VLANs, all routers on a given VLAN intended to route

multicast packets must have a least one common subnet on that VLAN. Use this

command when the VLAN is configured with multiple IP addresses (multinetting) to

specify the IP address to use as the source address for PIM protocol packets outbound

on the VLAN.

• Use ip-address to designate a single subnet in cases where multicast routers

on the same multinetted VLAN are not configured with identical sets of subnet

IP addresses.

• Use all if the multinetted VLAN is configured with the same set of subnet

addresses.

Default: the primary VLAN

Changing the frequency at which the routing switch transmits PIM hello messages on

the current VLAN

Syntax:

ip pim-dense [ hello-interval 5-30 ]

vlan [vid]ip pim-dense [hello-interval 5-30]

Changes the frequency at which the routing switch transmit PIM hello messages on

the current VLAN. The routing switch uses hello packets to inform neighboring

routers of its presence. The routing switch also uses this setting to compute the hello

hold time, which is included in hello packets sent to neighbor routers. hello hold

time tells neighbor routers how long to wait for the next hello packet from the routing

switch. If another packet does not arrive within that time, the router removes the

neighbor adjacency on that VLAN from the routing table, which removes any flows

running on that interface.

Shortening the hello interval reduces the hello hold time. This has the effect of

changing how quickly other routers will stop sending traffic to the routing switch if

they do not receive a new hello packet when expected.

NOTE: Not used with the [no]form of the ip pim-dense command.

Example:

If multiple routers are connected to the same VLAN and the routing switch requests

multicast traffic, all routers on the VLAN receive that traffic. (Those that have pruned

the traffic will drop it when they receive it.)

If the upstream router loses contact with the routing switch receiving the multicast

traffic (that is, fails to receive a hello packet when expected), the shorter hello

40 PIM-DM (Dense Mode)