Cisco Systems Configuring a Bidirectional Neighbor Filter

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Cisco ASA 5500 Series Configuration Guide using ASDM
Chapter29 Configuring Multicast Routing
Customizing Multicast Routing
The Add/Edit/Insert Neighbor Filter Entry dialog box appears. The Add/Edit/Insert Neighbor Filter
Entry dialog box lets you create the ACL entries for the multicast boundary ACL. You can also delete a
selected PIM neighbor entry.
Step3 Choose the interface name from the Interface Name drop-down list.
Step4 From the Action drop-down list, choose Permit or Deny for the neighbor filter ACL entry.
Choosing Permit allows the multicast group advertisements to pass through the interface. Choosing
Deny prevents the specified multicast group advertisements from passing through the interface. When a
multicast boundary is configured on an interface, all multicast traffic is prevented from passing through
the interface unless permitted with a neighbor filter entry.
Step5 In the IP Address text field, enter the IP address of the multicast PIM group being permitted or denied.
Valid group addresses range from 224.0.0.0 to 239.255.255.255.255.
Step6 From the Netmask drop-down list, choose the netmask for the multicast group address.
Step7 Click OK.
Configuring a Bidirectional Neighbor Filter
The Bidirectional Neighbor Filter pane shows the PIM bidirectional neighbor filters, if any, that are
configured on the ASA. A PIM bidirectional neighbor filter is an ACL that defines the neighbor devices
that can participate in the DF election. If a PIM bidirectional neighbor filter is not configured for an
interface, then there are no restrictions. If a PIM bidirectional neighbor filter is configured, only those
neighbors permitted by the ACL can participate in the DF election process.
When a PIM bidirectional neighbor filter configuration is applied to the ASA, an ACL appears in the
running configuration with the name interface-name_multicast, in which the interface-name is the name
of the interface to which the multicast boundary filter is applied. If an ACL with that name already exists,
a number is appended to the name (for example, inside_multicast_1). This ACL defines which devices
can become PIM neighbors of the ASA.
Bidirectional PIM allows multicast routers to keep reduced state information. All of the multicast routers
in a segment must be bidirectionally enabled for bidir to elect a DF.
The PIM bidirectional neighbor filters enable the transition from a sparse-mode-only network to a bidir
network by letting you specify the routers that should participate in the DF election, while still allowing
all routers to participate in the sparse-mode domain. The bidir-enabled routers can elect a DF from
among themselves, even when there are non-bidir routers on the segment. Multicast boundaries on the
non-bidir routers prevent PIM messages and data from the bidir groups from leaking in or out of the bidir
subset cloud.
When a PIM bidirectional neighbor filter is enabled, the routers that are permitted by the ACL are
considered to be bidirectionally capable. Therefore, the following is true:
•If a permitted neighbor does not support bidir, then the DF election does not occur.
•If a denied neighbor supports bidir, then the DF election does not occur.
•If a denied neighbor does not support bidir, the DF election can occur.
To define the neighbors that can become a PIM bidirectional neighbor filter, perform the following steps:
Step1 In the main ASDM window, choose Configuration > Device Setup > Routing > Multicast > PIM >
Bidirectional Neighbor Filter.