Cisco Sg2008 Manual
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8 Cisco Small Business SG200 Series 8-port Smart Switch 131 Multicast This chapter describes how to configure the multicast protocols that forward packets from one source to multiple destinations. It contains the following topics: •Multicast Properties •Configuring MAC Group Addresses •Configuring Group-to-Port •Configuring IGMP Snooping •Configuring MLD Snooping •Configuring IGMP Multicast Router Interfaces •Configuring MLD Multicast Router Interfaces Multicast protocols deliver packets from one source to multiple receivers. They facilitate better bandwidth utilization and help to reduce the processing load on hosts and routers, making them ideal for use in applications such as video and audio conferencing, whiteboard tools, and stock distribution tickers. The switch maintains a multicast forwarding table to make forwarding decisions for packets that arrive with a multicast destination MAC address. When multicasts are restricted only to specified ports, traffic is prevented from going to parts of the network where there are no receivers. When a packet enters the switch, the destination MAC address is combined with the VLAN ID and a search is performed in the multicast forwarding table. If no match is found, then the packet is either flooded to all ports in the VLAN or discarded, depending on the switch configuration. If a match is found, the packet is forwarded only to the ports that are members of that multicast group.
Multicast Multicast Properties Cisco Small Business SG200 Series 8-port Smart Switch 132 8 Multicast entries can be learned by snooping (listening in on) the layer 3 protocols that manage multicast memberships: •IPv4 multicast group addresses can be learned through the Internet Group Management protocol (IGMP). •IPv6 multicast group addresses can be learned through the Multicast Listener Discovery (MLD) protocol. Interfaces with IGMP and MLD multicast routers for a specific VLAN can be either statically or dynamic configured. The multicast routers use IGMP and MLD to manage the membership of the multicast groups. A multicast router is also required in order for the switch to support IGMP/MLD snooping properly in a VLAN. Multicast Properties You can use the Multicast Proper ties page to specify how multicast packets are for warded within VL ANs . When you create a VLAN, a default multicast forwarding option is assigned. You can use the Global Multicast Mode setting to set all VLANs currently configured on the switch to a selected forwarding mode. The global setting does not create a default setting for VLANs created subsequently—it simply ensures that all existing VLANs are configured with the specified mode. You can also configure how the switch forwards multicast packets on an individual or per-VLAN basis. Configuring a Multicast Forwarding Mode on all VLANs To configure all current VLANs with a particular multicast forwarding mode: STEP 1Click Multicast > Properties in the navigation window. STEP 2Select a Global Multicast Mode to apply to all VLANs. If a VLAN has been configured with a different mode, it is reset to the following mode: •Forward Unregistered—If a packet is received from a VLAN with a multicast destination address and no ports in the VLAN are registered to receive multicast packets for that address, then the packet is flooded to all ports in the VLAN. The responsibility for accepting or dropping the packets belongs to the hosts. If a multicast packet is received and there are ports registered to receive it, the packet is sent only to the registered ports.
Multicast Configuring MAC Group Addresses Cisco Small Business SG200 Series 8-port Smart Switch 133 8 •Forward All—All multicast packets received from a VLAN are flooded to all ports in the VLAN, regardless of port registrations to multicast addresses. •Filter Unregistered—If a packet is received from a VLAN for a multicast destination address and no ports in the VLAN are registered to receive multicast packets for that address, then the packets are dropped. STEP 3Click Apply. Your changes are saved to the Running Configuration. Configuring Multicast Properties on an Individual VLAN To configure a VLAN to have a different forwarding mode than the Global Multicast Mode setting: STEP 1Select the VLAN from the VLAN ID menu and click Edit. STEP 2Select the Multicast Mode as described in Configuring a Multicast Forwarding Mode on all VLANs. STEP 3Click Apply and then click Close. Your changes are saved to the Running Configuration. Configuring MAC Group Addresses The MAC Group Address page enables you to view and configure associations between multicast group MAC address and VLANs on the switch. You can configure static associations or they can be learned dynamically through IGMP or MLD snooping. When a packet is received for a multicast group address that matches an entry in the MAC Group Address Table, the packet is sent only to ports that are members of the VLAN. The switch supports up to 256 IPv4 and IPv6 MAC group address table entries, static and dynamic combined. A dynamic entry is aged out if no packets are received for the MAC group address for a configurable time (see the IGMP Snooping page to configure the IGMP Group Membership interval).
Multicast Configuring MAC Group Addresses Cisco Small Business SG200 Series 8-port Smart Switch 134 8 Viewing the MAC Group Address Table To view the MAC Group Address Table, click Multicast > MAC Group Address in the navigation window. By default, all entries display in the table. You can use the VLAN ID and MAC Group Address filters to display only entries that match the specified values. The following fields display: •Type—Indicates whether the entry is statically configured or dynamically learned. •VLAN ID—VLAN ID to which multicast packets are forwarded when they match the specified multicast MAC address. •MAC Group Address—Multicast group MAC address in hexadecimal format that is compared to an incoming packet destination MAC address. Adding a Static MAC Group Address Table Entry To add a static multicast MAC address and associate it with a VLAN: STEP 1Click Add on the MAC Group Address page. STEP 2Enter the parameters: •VLAN ID—Select a VLAN from the list. •Address Type—Select IPv4 to specify an address in 32-bit IPv4 notation (xxx.xxx.xxx.xxx), or select MAC to specify the address in a 6-byte hexadecimal format (xx.xx.xx.xx.xx.xx). •MAC Group Address—Enter the address in the selected format. For an IPv4 address, the least significant 23 bits are mapped to an Ethernet MAC address. STEP 3Click Apply and then click Close. The entry appears in the MAC Group Address Table.
Multicast Configuring Group-to-Port Cisco Small Business SG200 Series 8-port Smart Switch 135 8 Configuring MAC Address Group Port Membership By default, packets destined to a multicast MAC address are flooded on all ports. Ports might become members of a particular MAC address group dynamically through the exchange of IGMP packets, or you can statically configure them as members. To view details and configure the port members of a multicast group address: STEP 1Select an entry on the MAC Group Address page and click Details. The page identifies the members of the multicast group address on every port. STEP 2Click Static to configure a port as a static member of the multicast MAC address. Or click None to remove the port as a static member of the MAC Multicast Address. STEP 3Click Apply and then click Close. Your changes are saved to the Running Configuration. Configuring Group-to-Port The Group to Por t page enables you to configure associations between VLANs and multicast group MAC address on the switch. You can configure static associations or they can be learned dynamically through IGMP or MLD snooping. (see the IGMP Snooping page to configure the IGMP Group Membership interval) The results can be displayed in the MAC Group Address Table. To configure Group to Port: STEP 1Click Multicast > Group to Port in the navigation window. STEP 2Use the VLAN ID and MAC Group Address filters to display entries that match the specified values: •VLAN ID equals to—Select the VLAN ID to which multicast packets are forwarded when they match the specified multicast MAC address. •MAC Group Address equals to—Select the group MAC address that is compared to an incoming packet destination MAC address. STEP 3Select the Filter.
Multicast Configuring IGMP Snooping Cisco Small Business SG200 Series 8-port Smart Switch 136 8 STEP 4Set the type to indicate whether the entry is statically configured or dynamically learned. Ports can become members of a particular MAC address group dynamically through the exchange of IGMP packets, or you can statically configure them as members. STEP 5Click Apply. Your changes are saved to the Running Configuration. Configuring IGMP Snooping Internet Group Management Protocol (IGMP) is a layer 3 Internet protocol that enables IPv4 networks to manage memberships to multicast groups. (IPv6 multicast traffic is managed using the MLD protocol, as described in Configuring MLD Snooping.) IGMP communication occurs between IGMP routers and IGMP- enabled hosts (clients). Although the switch does not initiate or reply to IGMP packets, it can be configured to listen to IGMP communication between routers and clients that are connected by the switch, and to make forwarding decisions that help to reduce unnecessary network traffic.This listening behavior is referred to as IGMP snooping. This is particularly beneficial for high-bandwidth multicast network traffic. Ordinarily, when the switch receives broadcast or multicast packets, the switch forwards a copy into each of the remaining network segments. This approach works well for broadcast packets that are intended to be processed by all connected nodes. For multicast packets, however, this approach could lead to less efficient use of network bandwidth, particularly when the packet is intended for only a small number of nodes; packets are flooded into network segments where no node has an interest in receiving the packet. IGMP snooping enables the switch to intercept membership reports from IGMP clients and queries from routers. If the intercepted communications indicate that no IGMP clients exist on a link for a particular multicast destination address within a VLAN, then the switch does not send copies of those multicast packets to that network segment. IGMP snooping can be enabled or disabled on each VLAN. When enabled on a VLAN, IGMP snooping is performed on all interfaces that are members of that VLAN. Although IGMP is based on IP multicast addresses, the switch performs the actual multicast forwarding based on the equivalent MAC addresses.
Multicast Configuring IGMP Snooping Cisco Small Business SG200 Series 8-port Smart Switch 137 8 To configure IGMP snooping: STEP 1Click Multicast > IGMP Snooping in the navigation window. STEP 2Select Enable for the IGMP Snooping Status. STEP 3Click Add in the IGMP Snooping Table. STEP 4For VLAN ID, select the VLAN that is to support IGMP snooping. STEP 5Configure the following settings: •IGMP Fast Leave—Select Enable to allow the switch to immediately remove a port (or LAG) from its multicast forwarding table when it receives an IGMP leave message for that multicast group. When enabled, the switch removes the port without first sending out general queries to the interface. Enable Fast Leave mode only on VLANs where only one host is connected to each port. This prevents the inadvertent dropping of the other hosts that are connected to the same port and remain interested in receiving multicast traffic directed to that group. •IGMP Group Membership Interval—Specify the time in seconds that the switch waits for an IGMP membership report from a particular group on a particular interface before deleting the interface from the multicast forwarding database entry. Select Default to specify 260 seconds, or select User Defined and enter a value in the range 2 to 3600 seconds. •IGMP Max Response Time—Specify the time in seconds that the switch waits for a reply after sending a query on an interface because it did not receive a report for a particular group in that interface. This value must be less than the IGMP Group Membership Interval value. Select Default to specify 10 seconds, or select User Defined and enter a value in the range 1 to 25 seconds. •IGMP MRouter Expiry Time—Specify the time in seconds that the switch waits for a query to be received on an dynamic mrouter interface before the interface is removed from the VLAN. A value of 0 indicates an infinite timeout; i.e., no expiration. Select Default to specify 0 seconds, or select User Defined and enter a value in the range 0 to 3600 seconds. STEP 6Click Apply and then click Close. Your changes are saved to the Running Configuration. The new VLAN entry appears in the IGMP Snooping Table.
Multicast Configuring MLD Snooping Cisco Small Business SG200 Series 8-port Smart Switch 138 8 STEP 7Ensure that an IGMP Mrouter interface has been configured for this VLAN (or all VLANs). See Configuring IGMP Multicast Router Interfaces. Configuring MLD Snooping MLD is a protocol used by IPv6 multicast routers to discover the presence of multicast listeners (nodes wishing to receive IPv6 multicast packets) on its directly-attached links and to discover which multicast packets are of interest to neighboring nodes. MLD is derived from IGMP, which performs a similar function for IPv4 multicast traffic (see Configuring IGMP Snooping). When MLD snooping is enabled, the switch selectively forwards IPv6 multicast packets to a list of ports that want to receive the data instead of flooding the packets to all ports in the VLAN. This list is constructed by snooping IPv6 multicast control packets. NOTEThe switch supports MLD snooping of MLD version 1 and version 2 packets. The switch can be configured to perform MLD snooping and IGMP snooping simultaneously. MLD snooping can be enabled or disabled separately on each VLAN. Although MLD is based on IPv6 addresses, the switch performs the actual multicast forwarding based on the equivalent MAC addresses. To enable and configure MLD snooping: STEP 1Click Multicast > MLD Snooping in the navigation window. The MLD Snooping Table lists each VLAN on which this feature is enabled. STEP 2Select Enable for the MLD Snooping Status. STEP 3Click Add in the MLD Snooping Table.
Multicast Configuring MLD Snooping Cisco Small Business SG200 Series 8-port Smart Switch 139 8 STEP 4For VLAN ID, select the VLAN that is to support MLD snooping. STEP 5Enter the parameters: •MLD Fast Leave Mode—Select Enable to allow the switch to immediately remove a port (or LAG) from its multicast forwarding table when it receives an MLD leave message for that multicast group. When enabled, the switch removes the port without first sending out MAC-based general queries to the interface. Enable Fast Leave mode only on VLANs in which only one host is connected to each port. This prevents the inadvertent dropping of the other hosts that are connected to the same port and remain interested in receiving multicast traffic directed to that group. •MLD Group Membership Interval—Specify the time in seconds that the switch waits for an MLD membership report from a particular group on a particular interface before deleting the interface from the multicast forwarding database entry. Select Default to specify 260 seconds, or select User Defined and enter a value in the range 2 to 3600 seconds. •MLD Max Response Time—Specify the time in seconds that the switch waits for a reply after sending a query on an interface because it did not receive a report for a particular group in that interface. This value must be less than the MLD Group Membership Interval value. Select Default to specify 10 seconds, or select User Defined and enter a value in the range 1 to 65 seconds. •MLD Mrouter Expiry Time—Specify the time in seconds that the switch waits for a query to be received on an interface before the interface is removed from the list of interfaces with an MLD multicast router attached. A value of 0 indicates an infinite timeout; i.e., no expiration. Select Default to specify 0 seconds, or select User Defined and enter a value in the range 0 to 3600 seconds. STEP 6Click Apply and then click Close. The new VLAN entry appears in the MLD Snooping Table. STEP 7Ensure that an MLD Mrouter interface has been configured for this VLAN. See Configuring MLD Multicast Router Interfaces.
Multicast Configuring IGMP Multicast Router Interfaces Cisco Small Business SG200 Series 8-port Smart Switch 140 8 Configuring IGMP Multicast Router Interfaces An IGMP router must exist to manage the IGMP clients in a VLAN. For each VLAN that supports IGMP snooping, the switch must be statically configured with or must dynamically learn one or more interfaces where there is an IGMP router. An interface that has an IGMP router is known a IGMP Multicast router Interface. A VLAN that is IGMP snooping-enabled must have one or more IGMP multicast router interfaces. An IGMP multicast router can serve one or more VLANs. To enable a switch port or LAG as an IGMP Mrouter interface and to configure related settings: STEP 1Click Multicast > IGMP Mrouter in the navigation window By default, the IGMP MRouter Table lists each switch port. To show LAGs, select LAG from the Interface Type list. STEP 2Select the port or LAG that you want to configure and click Edit. STEP 3Select Enable for the Mode. STEP 4To specify the VLANs that use this interface as the IGMP Mrouter interface, move the VLAN to the Selected list, as described below. •To select a VLAN: Click a VLAN in the Available list, and then click the right- arrow button to move it to the Selected list. •To remove a VLAN: Click a VLAN in the Selected list, and then click the left- arrow button to move it to the Available list. STEP 5Click Apply and then click Close. In the IGMP Mrouter Table, the interface displays Enable in the Mode column and lists the selected VLANs.