ASDM Book 1: Cisco ASA Series General Operations ASDM Configuration Guide, 7.2

Stub Multicast Routing

Stub multicast routing provides dynamic host registration and facilitates multicast routing. When configured for stub multicast routing, the ASA acts as an IGMP proxy agent. Instead of fully participating in multicast routing, the ASA forwards IGMP messages to an upstream multicast router, which sets up delivery of the multicast data. When configured for stub multicast routing, the ASA cannot be configured for PIM.

The ASA supports both PIM-SM and bidirectional PIM. PIM-SM is a multicast routing protocol that uses the underlying unicast routing information base or a separate multicast-capable routing information base. It builds unidirectional shared trees rooted at a single Rendezvous Point per multicast group and optionally creates shortest-path trees per multicast source.

PIM Multicast Routing

Bi-directional PIM is a variant of PIM-SM that builds bi-directional shared trees connecting multicast sources and receivers. Bi-directional trees are built using a DF election process operating on each link of the multicast topology. With the assistance of the DF, multicast data is forwarded from sources to the Rendezvous Point, and therefore along the shared tree to receivers, without requiring source-specific state. The DF election takes place during Rendezvous Point discovery and provides a default route to the Rendezvous Point.

Note If the ASA is the PIM Rendezvous Point, use the untranslated outside address of the ASA as the Rendezvous Point address.

Multicast Group Concept

Multicast is based on the concept of a group. An arbitrary group of receivers expresses an interest in receiving a particular data stream. This group does not have any physical or geographical boundaries—the hosts can be located anywhere on the Internet. Hosts that are interested in receiving data flowing to a particular group must join the group using IGMP. Hosts must be a member of the group to receive the data stream. For information about how to configure multicast groups, see Configuring a Multicast Group.

Multicast Addresses

Multicast addresses specify an arbitrary group of IP hosts that have joined the group and want to receive traffic sent to this group.

Clustering

Multicast routing supports clustering. In Layer 2 clustering, the master unit sends all multicast routing packets and data packets until fast-path forwarding is established. After fast-path forwarding is established, slave units may forward multicast data packets. All data flows are full flows. Stub forwarding flows are also supported. Because only one unit receives multicast packets in Layer 2 clustering, redirection to the master unit is common. In Layer 3 clustering, units do not act independently. All data and routing packets are processed and forwarded by the master unit. Slave units drop all packets that have been sent.

For more information about clustering, see Chapter9, “ASA Cluster”

Configuring Stub Multicast Routing and Forwarding IGMP Messages

Note Stub multicast routing and PIM are not supported concurrently.

An ASA acting as the gateway to the stub area does not need to participate in PIM. Instead, you can configure it to act as an IGMP proxy agent and forward IGMP messages from hosts connected on one interface to an upstream multicast router on another interface. To configure the ASA as an IGMP proxy agent, forward the host join and leave messages from the stub area interface to an upstream interface.

To forward the host join and leave messages, perform the following steps:

Step 1 In the main ASDM window, choose Configuration > Device Setup > Routing > Multicast.

Step 2 In the Multicast pane, check the Enable Multicast routing check box.

Step 3 Click Apply to save your changes.

Step 4 Choose Configuration > Device Setup > Routing > Multicast > IGMP > Protocol.

Step 5 To modify the specific interface from which you want to forward IGMP messages, select the interface and click Edit.

The Configure IGMP Parameters dialog box appears.

Step 6 From the Forward Interface drop-down list, choose the specific interface from which you want to forward IGMP messages.

Step 7 Click OK to close this dialog box, then click Apply to save your changes.

Configuring a Static Multicast Route

Configuring static multicast routes lets you separate multicast traffic from unicast traffic. For example, when a path between a source and destination does not support multicast routing, the solution is to configure two multicast devices with a GRE tunnel between them and to send the multicast packets over the tunnel.

When using PIM, the ASA expects to receive packets on the same interface where it sends unicast packets back to the source. In some cases, such as bypassing a route that does not support multicast routing, you may want unicast packets to take one path and multicast packets to take another.

Static multicast routes are not advertised or redistributed.

To configure a static multicast route or a static multicast route for a stub area, perform the following steps:

Step 1 In the main ASDM window, choose Configuration > Device Setup > Routing > Multicast > MRoute.

Step 2 Choose Add or Edit.

The Add or Edit Multicast Route dialog box appears.

Use the Add Multicast Route dialog box to add a new static multicast route to the ASA. Use the Edit Multicast Route dialog box to change an existing static multicast route.

Step 3 In the Source Address field, enter the IP address of the multicast source. You cannot change this value when editing an existing static multicast route.

Step 4 Choose the network mask for the IP address of the multicast source from the Source Mask drop-down list.

Step 5 In the Incoming Interface area, click either the RPF Interface radio button to choose RPF to forward the route or the Interface Name radio button, then enter the following:

• In the Source Interface field, choose the incoming interface for the multicast route from the drop-down list.
• In the Destination Interface field, choose the destination interface that the route is forwarded through from the drop-down list.

Note You can specify the interface or the RPF neighbor, but not both at the same time.

Step 6 In the Administrative Distance field, choose the administrative distance of the static multicast route. If the static multicast route has the same administrative distance as the unicast route, then the static multicast route takes precedence.

Step 7 Click OK.

Configuring IGMP Features

IP hosts use the Internet Group Management Protocol (IGMP) to report their group memberships to directly connected multicast routers.

IGMP is used to dynamically register individual hosts in a multicast group on a particular LAN. Hosts identify group memberships by sending IGMP messages to their local multicast router. Under IGMP, routers listen to IGMP messages and periodically send out queries to discover which groups are active or inactive on a particular subnet.

IGMP uses group addresses (Class D IP address) as group identifiers. Host group address can be in the range of 224.0.0.0 to 239.255.255.255. The address 224.0.0.0 is never assigned to any group. The address 224.0.0.1 is assigned to all systems on a subnet. The address 224.0.0.2 is assigned to all routers on a subnet.

When you enable multicast routing on the ASA, IGMP Version 2 is automatically enabled on all interfaces.

Note Only the no igmp command appears in the interface configuration when you use the show run command. If the multicast-routing command appears in the device configuration, then IGMP is automatically enabled on all interfaces.

This section describes how to configure optional IGMP setting on a per-interface basis and includes the following topics:

• Disabling IGMP on an Interface
• Configuring IGMP Group Membership
• Configuring a Statically Joined IGMP Group
• Controlling Access to Multicast Groups
• Limiting the Number of IGMP States on an Interface
• Modifying the Query Messages to Multicast Groups
• Changing the IGMP Version

Disabling IGMP on an Interface

You can disable IGMP on specific interfaces. This information is useful if you know that there are no multicast hosts on a specific interface and you want to prevent the ASA from sending host query messages on that interface.

To disable IGMP on an interface, perform the following steps:

Step 1 In the main ASDM window, choose Configuration > Device Setup > Routing > Multicast > IGMP > Protocol.

The Protocol pane displays the IGMP parameters for each interface on the ASA.

Step 2 Choose the interface that you want to disable and click Edit.

Step 3 To disable the specified interface, uncheck the Enable IGMP check box.

Step 4 Click OK.

The Protocol pane displays Yes if IGMP is enabled on the interface, or No if IGMP is disabled on the interface.

Configuring IGMP Group Membership

You can configure the ASA to be a member of a multicast group. Configuring the ASA to join a multicast group causes upstream routers to maintain multicast routing table information for that group and keep the paths for that group active.

Note If you want to forward multicast packets for a specific group to an interface without the ASA accepting those packets as part of the group, see Configuring a Statically Joined IGMP Group.

To have the ASA join a multicast group, perform the following steps:

Step 1 In the main ASDM window, choose Configuration > Device Setup > Routing > Multicast > IGMP > Join Group.

The Join Group pane appears.

Step 2 Click Add or Edit.

The Add IGMP Join Group dialog box allows you to configure an interface to be a member of a multicast group. The Edit IGMP Join Group dialog box allows you to change existing membership information.

Step 3 In the Interface Name field, choose the interface name from the drop-down list. If you are editing an existing entry, you cannot change this value.

Step 4 In the Multicast Group Address field, enter the address of a multicast group to which the interface belongs. Valid group addresses range from 224.0.0.0 to 239.255.255.255.

Step 5 Click OK.

Configuring a Statically Joined IGMP Group

Sometimes a group member cannot report its membership in the group because of some configuration, or there may be no members of a group on the network segment. However, you still want multicast traffic for that group to be sent to that network segment. You can have multicast traffic for that group sent to the segment by configuring a statically joined IGMP group.

In the main ASDM window, choose Configuration > Routing > Multicast > IGMP > Static Group to configure the ASA to be a statically connected member of a group. With this method, the ASA does not accept the packets itself, but only forwards them. Therefore, this method allows fast switching. The outgoing interface appears in the IGMP cache, but this interface is not a member of the multicast group.

To configure a statically joined multicast group on an interface, perform the following steps:

Step 1 In the main ASDM window, choose Configuration > Device Setup > Routing > Multicast > IGMP > Static Group.

The Static Group pane appears.

Step 2 Click Add or Edit.

Use the Add IGMP Static Group dialog box to statically assign a multicast group to an interface. Use the Edit IGMP Static Group dialog box to change existing static group assignments.

Step 3 In the Interface Name field, choose the interface name from the drop-down list. If you are editing an existing entry, you cannot change this value.

Step 4 In the Multicast Group Address field, enter the address of a multicast group to which the interface belongs. Valid group addresses range from 224.0.0.0 to 239.255.255.255.

Step 5 Click OK.

Controlling Access to Multicast Groups

To control the multicast groups that hosts on the ASA interface can join, perform the following steps:

Step 1 In the main ASDM window, choose Configuration > Device Setup > Routing > Multicast > IGMP > Access Group.

The Access Group pane appears. The table entries in the Access Group pane are processed from the top down. Place more specific entries near the top of the table and more generic entries further down. For example, place an access group entry that permits a specific multicast group near the top of the table and an access group entry below that denies a range of multicast groups, including the group in the permit rule. The group is permitted because the permit rule is enforced before the deny rule.

Double-clicking an entry in the table opens the Add or Edit Access Group dialog box for the selected entry.

Step 2 Click Add or Edit.

The Add Access Group or Edit Access Group dialog box appears. The Add Access Group dialog box lets you add a new access group to the Access Group Table. The Edit Access Group dialog box lets you change information for an existing access group entry. Some fields may be dimmed when editing existing entries.

Step 3 Choose the interface name with which the access group is associated from the Interface drop-down list. You cannot change the associated interface when you are editing an existing access group.

Step 4 Choose permit from the Action drop-down list to allow the multicast group on the selected interface. Choose deny from the Action drop-down list to filter the multicast group from the selected interface.

Step 5 In the Multicast Group Address field, enter the address of the multicast group to which the access group applies.

Step 6 Enter the network mask for the multicast group address, or choose one of the common network masks from the Netmask drop-down list.

Step 7 Click OK.

Limiting the Number of IGMP States on an Interface

You can limit the number of IGMP states resulting from IGMP membership reports on a per-interface basis. Membership reports exceeding the configured limits are not entered in the IGMP cache, and traffic for the excess membership reports is not forwarded.

To limit the number of IGMP states on an interface, perform the following steps:

Step 1 In the main ASDM window, choose Configuration > Device Setup > Routing > Multicast > IGMP > Protocol.

Step 2 Choose the interface you want to limit from the table on the Protocol pane, and click Edit.

The Configure IGMP Parameters dialog box appears.

Step 3 In the Group Limit field, enter the maximum number of host that can join on an interface. Valid values range from 0 to 500. The default value is 500. Setting this value to 0 prevents learned groups from being added, but manually defined memberships are still permitted.

Step 4 Click OK.

Modifying the Query Messages to Multicast Groups

The ASA sends query messages to discover which multicast groups have members on the networks attached to the interfaces. Members respond with IGMP report messages indicating that they want to receive multicast packets for specific groups. Query messages are addressed to the all-systems multicast group, which has an address of 224.0.0.1, with a time-to-live value of 1.

These messages are sent periodically to refresh the membership information stored on the ASA. If the ASA discovers that there are no local members of a multicast group still attached to an interface, it stops forwarding multicast packet for that group to the attached network, and it sends a prune message back to the source of the packets.

By default, the PIM designated router on the subnet is responsible for sending the query messages. By default, they are sent once every 125 seconds.

When changing the query response time, by default, the maximum query response time advertised in IGMP queries is 10 seconds. If the ASA does not receive a response to a host query within this amount of time, it deletes the group.

To change the query interval, query response time, and query timeout value, perform the following steps:

Step 1 In the main ASDM window, choose Configuration > Device Setup > Routing > Multicast > IGMP > Protocol.

Step 2 Choose the interface you want to limit from the table on the Protocol pane, and click Edit.

The Configure IGMP Parameters dialog box appears.

Step 3 In the Query Interval field, enter the interval, in seconds, at which the designated router sends IGMP host-query messages. Valid values range from 1 to 3600 seconds. The default value is 125 seconds.

Step 4 In the Query Timeout field, enter the period of time, in seconds, before which the ASA takes over as the requester for the interface after the previous requester has stopped doing so. Valid values range from 60 to 300 seconds. The default value is 255 seconds.

Step 5 Click OK.

Changing the IGMP Version

By default, the ASA runs IGMP Version 2, which enables several additional features.

All multicast routers on a subnet must support the same version of IGMP. The ASA does not automatically detect Version 1 routers and switch to Version 1. However, a mix of IGMP Version 1 and 2 hosts on the subnet works; the ASA running IGMP Version 2 works correctly when IGMP Version 1 hosts are present.

To control which version of IGMP is running on an interface,perform the following steps:

Step 1 In the main ASDM window, choose Configuration > Device Setup > Routing > Multicast > IGMP > Protocol.

Step 2 Choose the interface whose version of IGMP you want to change from the table on the Protocol pane, and click Edit.

The Configure IGMP Interface dialog box appears.

Step 3 Choose the version number from the Version drop-down list.

Step 4 Click OK.

Configuring PIM Features

Routers use PIM to maintain forwarding tables for forwarding multicast diagrams. When you enable multicast routing on the ASA, PIM and IGMP are automatically enabled on all interfaces.

Note PIM is not supported with PAT. The PIM protocol does not use ports, and PAT only works with protocols that use ports.

This section describes how to configure optional PIM settings and includes the following topics:

• Enabling and Disabling PIM on an Interface
• Configuring a Static Rendezvous Point Address
• Configuring the Designated Router Priority
• Configuring and Filtering PIM Register Messages
• Configuring PIM Message Intervals
• Configuring a Route Tree
• Filtering PIM Neighbors

Enabling and Disabling PIM on an Interface

You can enable or disable PIM on specific interfaces. To enable or disable PIM on an interface, perform the following steps:

Step 1 In the main ASDM window, choose Configuration > Device Setup > Routing > Multicast > PIM > Protocol.

Step 2 Choose the interface on which you want to enable PIM from the table on the Protocol pane, and click Edit.

The Edit PIM Protocol dialog box appears.

Step 3 Check the Enable PIM check box. To disable PIM, uncheck this check box.

Step 4 Click OK.

Configuring a Static Rendezvous Point Address

All routers within a common PIM sparse mode or bidir domain require knowledge of the PIM RP address. The address is statically configured using the pim rp-address command.

Note The ASA does not support Auto-RP or PIM BSR

You can configure the ASA to serve as RP to more than one group. The group range specified in the ACL determines the PIM RP group mapping. If an ACL is not specified, then the RP for the group is applied to the entire multicast group range (224.0.0.0/4).

To configure the address of the PIM PR, perform the following steps:

Note The ASA always advertises the bidirectional capability in the PIM hello messages, regardless of the actual bidirectional configuration.

Step 1 In the main ASDM window, choose Configuration > Device Setup > Routing > Multicast > PIM > Rendezvous Points.

Step 2 Click Add or Edit.

The Add or Edit Rendezvous Point dialog box appears. The Add Rendezvous Point dialog box lets you add a new entry to the Rendezvous Point table. The Edit Rendezvous Point dialog box lets you change an existing RP entry. Additionally, you can click Delete to remove the selected multicast group entry from the table.

These restrictions apply to RPs:

• You cannot use the same RP address twice.
• You cannot specify All Groups for more than one RP.

Step 3 In the Rendezvous Point Address field, enter the IP address for the RP.

When editing an existing RP entry, you cannot change this value.

Step 4 Check the Use bi-directional forwarding check box if the specified multicast groups are to operate in bidirectional mode. The Rendezvous Point pane displays Yes if the specified multicast groups are to operate in bidirectional mode and displays No if the specified groups are to operate in sparse mode. In bidirectional mode, if the ASA receives a multicast packet and has no directly connected members or PIM neighbors present, it sends a prune message back to the source.

Step 5 Click the Use this RP for All Multicast Groups radio button to use the specified RP for all multicast groups on the interface, or the Use this RP for the Multicast Groups as specified below radio button to designate the multicast groups to use with the specified RP.

For more information about multicast groups, see Configuring a Multicast Group.

Step 6 Click OK.

Configuring the Designated Router Priority

The DR is responsible for sending PIM register, join, and prune messages to the RP. When there is more than one multicast router on a network segment, selecting the DR is based on the DR priority. If multiple devices have the same DR priority, then the device with the highest IP address becomes the DR.

By default, the ASA has a DR priority of 1. To change this value, perform the following steps:

Step 1 In the main ASDM window, choose Configuration > Device Setup > Routing > Multicast > PIM > Protocol.

Step 2 Choose the interface that you want to enable for PIM from the table on the Protocol pane, and click Edit.

The Edit PIM Protocol dialog box appears.

Step 3 In the DR Priority field, type the value for the designated router priority for the selected interface. The router with the highest DR priority on the subnet becomes the designated router. Valid values range from 0 to 4294967294. The default DR priority is 1. Setting this value to 0 makes the ASA interface ineligible to become the default router.

Step 4 Click OK.

Configuring and Filtering PIM Register Messages

When the ASA is acting as an RP, you can restrict specific multicast sources from registering with it to prevent unauthorized sources from registering with the RP. The Request Filter pane lets you define the multicast sources from which the ASA will accept PIM register messages.

To filter PIM register messages, perform the following steps:

Step 1 In the main ASDM window, choose Configuration > Device Setup > Routing > Multicast > PIM > Request Filter.

Step 2 Click Add.

The Request Filter Entry dialog box lets you define the multicast sources that are allowed to register with the ASA when the ASA acts as an RP. You create the filter rules based on the source IP address and the destination multicast address.

Step 3 From the Action drop-down list, choose Permit to create a rule that allows the specified source of the specified multicast traffic to register with the ASA, or choose Deny to create a rule that prevents the specified source of the specified multicast traffic from registering with the ASA.

Step 4 In the Source IP Address field, type the IP address for the source of the register message.

Step 5 In the Source Netmask field, type or choose the network mask from the drop-down list for the source of the register message.

Step 6 In the Destination IP Address field, type the multicast destination address.

Step 7 In the Destination Netmask field, type or choose the network mask from the drop-down list for the multicast destination address.

Step 8 Click OK.

Configuring PIM Message Intervals

Router query messages are used to select the PIM DR. The PIM DR is responsible for sending router query messages. By default, router query messages are sent every 30 seconds. Additionally, every 60 seconds, the ASA sends PIM join or prune messages.

To change these intervals, perform the following steps:

Step 1 In the main ASDM window, choose Configuration > Device Setup > Routing > Multicast > PIM > Protocol.

Step 2 Choose the interface that you want to enable for PIM from the table on the Protocol pane, and click Edit.

The Edit PIM Protocol dialog box appears.

Step 3 In the Hello Interval field, type the frequency, in seconds, at which the interface sends PIM hello messages.

Step 4 In the Prune Interval field, type the frequency, in seconds, at which the interface sends PIM join and prune advertisements.

Step 5 Click OK.

Configuring a Route Tree

By default, PIM leaf routers join the shortest-path tree immediately after the first packet arrives from a new source. This method reduces delay, but requires more memory than the shared tree. You can configure whether or not the ASA should join the shortest-path tree or use the shared tree, either for all multicast groups or only for specific multicast addresses.

To configure a PIM leaf router tree, perform the following steps:

Step 1 In the main ASDM window, choose Configuration > Device Setup > Routing > Multicast > PIM > Route Tree.

Step 2 Click one of the following radio buttons:

• Use Shortest Path Tree for All Groups —Choose this option to use the shortest-path tree for all multicast groups.
• Use Shared Tree for All Groups —Choose this option to use the shared tree for all multicast groups.
• Use Shared Tree for the Groups specified below —Choose this option to use the shared tree for the groups specified in the Multicast Groups table. The shortest-path tree is used for any group that is not specified in the Multicast Groups table.

The Multicast Groups table displays the multicast groups to use with the shared tree.

The table entries are processed from the top down. You can create an entry that includes a range of multicast groups, but excludes specific groups within that range by placing deny rules for the specific groups at the top of the table and the permit rule for the range of multicast groups below the deny statements.

To edit a multicast group, see Configuring a Multicast Group.

Configuring a Multicast Group

Multicast groups are lists of access rules that define which multicast addresses are part of a group. A multicast group can include a single multicast address or a range of multicast addresses. Use the Add Multicast Group dialog box to create a new multicast group rule. Use the Edit Multicast Group dialog box to modify an existing multicast group rule.

To configure a multicast group, perform the following steps:

Step 1 In the main ASDM window, choose Configuration > Device Setup > Routing > Multicast > PIM > Rendezvous Points.

Step 2 The Rendezvous Point pane appears. Click the group that you want to configure.

The Edit Rendezvous Point dialog box appears.

Step 3 Click the Use this RP for the Multicast Groups as specified below radio button to designate the multicast groups to use with the specified RP.

Step 4 Click Add or Edit.

The Add or Edit Multicast Group dialog box appears.

Step 5 From the Action drop-down list, choose Permit to create a group rule that allows the specified multicast addresses, or choose Deny to create a group rule that filters the specified multicast addresses.

Step 6 In the Multicast Group Address field, type the multicast address associated with the group.

Step 7 From the Netmask drop-down list, choose the network mask for the multicast group address.

Step 8 Click OK.

Filtering PIM Neighbors

You can define the routers that can become PIM neighbors. By filtering the routers that can become PIM neighbors, you can do the following:

• Prevent unauthorized routers from becoming PIM neighbors.
• Prevent attached stub routers from participating in PIM.

To define neighbors that can become a PIM neighbor, perform the following steps:

Step 1 In the main ASDM window, choose Configuration > Device Setup > Routing > Multicast > PIM > Neighbor Filter.

Step 2 Choose the PIM neighbor that you want to configure from the table by clicking Add / Edit / Insert.

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.

Step 3 Choose the interface name from the Interface Name drop-down list.

Step 4 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.

Step 5 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.

Step 6 From the Netmask drop-down list, choose the netmask for the multicast group address.

Step 7 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:

Step 1 In the main ASDM window, choose Configuration > Device Setup > Routing > Multicast > PIM > Bidirectional Neighbor Filter.

Step 2 Double-click an entry in the PIM Bidirectional Neighbor Filter table to open the Edit Bidirectional Neighbor Filter Entry dialog box for that entry.

Step 3 Choose the PIM neighbor that you want to configure from the table by clicking Add / Edit / Insert.

The Add/Edit/Insert Bidirectional Neighbor Filter Entry dialog box appears, which lets you create ACL entries for the PIM bidirectional neighbor filter ACL

Step 4 Choose the interface name from the Interface Name drop-down list. Select the interface for which you are configuring the PIM bidirectional neighbor filter ACL entry.

Step 5 From the Action drop-down list, choose Permit or Deny for the neighbor filter ACL entry.

Choose Permit to allow the specified devices to participate in the DF election process. Choose Deny to prevent the specified devices from participating in the DF election process.

Step 6 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.

Step 7 From the Netmask drop-down list, choose the netmask for the multicast group address.

Step 8 Click OK.

Configuring a Multicast Boundary

Address scoping defines domain boundaries so that domains with RPs that have the same IP address do not leak into each other. Scoping is performed on the subnet boundaries within large domains and on the boundaries between the domain and the Internet.

You can set up an administratively scoped boundary on an interface for multicast group addresses by choosing Configuration > Routing > Multicast > MBoundary in ASDM. IANA has designated the multicast address range from 239.0.0.0 to 239.255.255.255 as the administratively scoped addresses. This range of addresses can be reused in domains administered by different organizations. The addresses would be considered local, not globally unique.

A standard ACL defines the range of affected addresses. When a boundary is set up, no multicast data packets are allowed to flow across the boundary from either direction. The boundary allows the same multicast group address to be reused in different administrative domains.

You can configure, examine, and filter Auto-RP discovery and announcement messages at the administratively scoped boundary. Any Auto-RP group range announcements from the Auto-RP packets that are denied by the boundary ACL are removed. An Auto-RP group range announcement is permitted and passed by the boundary only if all addresses in the Auto-RP group range are permitted by the boundary ACL. If any address is not permitted, the entire group range is filtered and removed from the Auto-RP message before the Auto-RP message is forwarded.

To configure a multicast boundary, perform the following steps:

Step 1 In the main ASDM window, choose Configuration > Routing > Multicast > MBoundary.

The MBoundary pane lets you configure a multicast boundary for administratively scoped multicast addresses. A multicast boundary restricts multicast data packet flows and enables reuse of the same multicast group address in different administrative domains. When a multicast boundary is defined on an interface, only the multicast traffic permitted by the filter ACL passes through the interface.

Step 2 Click Edit.

The Edit Boundary Filter dialog box appears and displays the multicast boundary filter ACL. You can add and remove boundary filter ACL entries using this dialog box.

When the boundary filter configuration is applied to the ASA, the ACL appears in the running configuration with the name interface-name _multicast, where 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).

Step 3 Choose the interface for which you are configuring the multicast boundary filter ACL from the Interface drop-down list.

Step 4 Check the Remove any Auto-RP group range check box to filter Auto-RP messages from sources denied by the boundary ACL. If the Remove any Auto-RP group range check box is unchecked, all Auto-RP messages are passed.

Step 5 Click OK.

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