About 'Static Multicast Configuration' on the N/S-Series

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Article ID: 9287 

Products
Matrix N-Series DFE, firmware 5.21.24 and higher
S-Series, all firmware 

Protocols/Features
Load balancing 

Related to
Microsoft
NLB 

Commands
'set mac multicast' 

Goals
Static scoping of Multicast streams
Static Multicast Configuration
Sample configuration 

Cause
N-Series firmware 5.21.24 release notes state, in the Firmware Changes and Enhancements section: 
"The CLI 'set mac multicast' command is used to configure static MAC addresses. Static Multicast MAC entries are bound to a VLAN and zero or more ports. Multicast frames matching these entries are transmitted on each of the specified ports that are currently egressing the specified VLAN. The dot1qStaticMulticastMIB in the qBridgeMIB may also be used to manage the multicast aspects of this feature. Up to 32 static multicast entries may be configured per system. 

This multicast feature will typically be used in networks supporting server clusters. Some server cluster configurations require the user to configure a static ARP entry with a multicast MAC address. By using this new feature the user can ensure fast hardware based forwarding as well as limit the ports transmitted on to those in the subject server cluster." 

This article describes the use of this feature. 

Solution
Static Multicast Configuration refers to the ability to set static multicast MAC addresses so that these addresses may be scoped to only targeted ports within that same VLAN. IGMP may further prune these flows by port if they fall under its purview. 

This design differs from the operation of the same command set on the Matrix E1 in that the N and S-Series scope the targeted multicast within the specified member vlan to specified member ports within the same vlan (does not copy multicast from one VLAN to another) while the E1 scopes the targeted multicast from the specified ingress VLAN to all ports allowed to egress the specified egress VLAN. 

A key purposes of this feature is to support the multicast version of various NIC-based proprietary "Load Balancing" technologies, including NLB (Microsoft's Network Load Balancing). These multicast streams are not typically constrained by IGMP, which scopes only frames of multicast destination MAC Address 01-00-5E-xx-xx-xx and a corresponding multicast destination IP Address. 

The 'set mac multicast' command set does not Load Balance in the absence of these third-party applications. 

Here is an example cli session demonstrating the command set:
  DFE(rw)->set mac ?
agetime Set timeout period for aging learned entries
multicast Set multicast MAC address properties
unicast Set unicast MAC address properties
DFE(rw)->set mac multicast ?
<mac-address> Multicast MAC address (ex. 01-01-F4-56-78-90)
DFE(rw)->set mac multicast A-B-C-D-E-F ?
<vlan-id> VLAN index [1..4094]
DFE(rw)->set mac multicast A-B-C-D-E-F 1 ?
<port-string> The port-list a frame with a specific address shall be
flooded or the address shall be dynamically learned on
append Append the following port-list to the 'egress-ports'
port-list
clear Clear the following port-list from the 'egress-ports'
port-list
<cr>
DFE(rw)->set mac multicast A-B-C-D-E-F 1 fe.0.1 ?
append Append the following port-list to the 'egress-ports'
port-list
clear Clear the following port-list from the 'egress-ports'
port-list
<cr>
DFE(rw)->set mac multicast A-B-C-D-E-F 1 fe.0.1 append ?
<cr>
DFE(rw)->set mac multicast A-B-C-D-E-F 1 fe.0.1 clear ?
<cr>
DFE(rw)->clear mac ?
all Clear all MAC address entries
address MAC address to clear (ex. 00-01-F4-56-78-90); if not
specified, clear command shall be scoped to all MAC
address
fid Filtering database id to clear; if not specified,
clear command shall be scoped to all filtering
database ids
vlan-id VLAN index [1..4094] (for static multicast entries)
port-string Single port to clear (ex. fe.1.1); if not specified,
clear command shall be scoped to all ports
type Status type to clear; if not specified, clear command
shall be scoped to all 'learned' and 'mgmt' types
agetime Clear timeout period to default value
DFE(rw)->clear mac address ?
<address> MAC address to clear (ex. 00-01-F4-56-78-90); if not
specified, clear command shall be scoped to all MAC
address
DFE(rw)->clear mac address A-B-C-D-E-F ?
fid Filtering database id to clear; if not specified,
clear command shall be scoped to all filtering
database ids
vlan-id VLAN index [1..4094] (for static multicast entries)
port-string Single port to clear (ex. fe.1.1); if not specified,
clear command shall be scoped to all ports
type Status type to clear; if not specified, clear command
shall be scoped to all 'learned' and 'mgmt' types
<cr>
DFE(rw)->clear mac address A-B-C-D-E-F vlan-id 1 ?
<cr>
DFE(rw)->show mac address ?
<mac-address> MAC address (ex. 00-01-F4-56-78-90)
DFE(rw)->show mac address A-B-C-D-E-F ?
fid Filter database id (ex. 3)
vlan-id VLAN index [1..4094] (for static multicast entries)
port-string Port or range of ports (default: all ports)
type Type (other | invalid | learned | self | mgmt)
field-decode Display the meanings of the fields for this CLI
command
-verbose Displays all information in detail
<cr>
DFE(rw)->

For example, assuming the command format 
  set mac multicast <MAC> <member VLAN> <member ports>... 

  • <MAC> - Traffic matching the configured destination multicast MAC Address is targeted for special handling if it has been ingressed onto the "member VLAN". This traffic may or may not be further constrained by the effects of IGMP.
  • <member VLAN> - This may be any VLAN containing any type of network equipment. The multicast traffic to be examined has already been assigned this VLAN ID, and the targeted multicast traffic will be suppressed from being forwarded to non-member ports (those not specified in the command).
  • <member ports> - The ports which will receive the targeted multicast traffic (if they also have been statically or dynamically permitted to egress the "member VLAN"). All other ports will not. Since only the (Load Sharing / Load Balancing / etc) server NICs need to see this multicast traffic, only those desired server ports (and not necessarily the multicast source port) will be named in this command. These devices will thus receive the desired multicast flows - in addition to the traffic they are receiving from (and transmitting onto) the VLAN by conventional means - collectively at line rate.

This sample DFE configuraton will accommodate a Load Sharing server with NICs plugged into ports fe.1.1-3 (cross-communicating via multicasting with a destination MAC of 01-00-00-11-11-11), while users potentially exist in any other ports. Though the users also originate multicast traffic of this type to begin conversations with the server, they need not see this traffic.
 set vlan 3 create  (S-Series: set vlan create 3) [create the general/multicast VLAN]
set port vlan fe.1.1-48 3 [assign all ingressed traffic to this VLAN]
set vlan egress 3 fe.1.1-48 untagged [allow all ports to egress this VLAN]
clear vlan egress 1 fe.1.1-48 [clear the default egress permissions]
set mac multicast 01-00-00-11-11-11 3 fe.1.1-3 [specify the MAC, member VLAN, and member ports]

To use the default VLAN 1 for this purpose, omit the first four commands and specify VLAN 1 in the fifth command. 

A maximum of 32 'set mac multicast' command iterations may be configured, with repetition allowed (but not required) for the same MAC, member VLAN, and/or member ports parameters. 

Further information is provided in the Configuration Guide relevant to your hardware and firmware. 
See also: 5708.
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