Cisco Sg3008 Manual

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Cisco Small Business 200, 300 and 500 Series Managed Switch Administration Guide (Internal Version)  246
 
Managing MAC Address Tables
This section describe how to add MAC addresses to the system. It covers the 
following topics:
•Configuring Static MAC Addresses
•Managing Dynamic MAC Addresses
•Defining Reserved MAC Addresses
Types of MAC Addresses
There are two types of MAC addresses—static and dynamic. Depending on their 
type, MAC addresses are either stored in the Static Address table or in the 
Dynamic Address table, along with VLAN and port information. 
Static addresses are configured by the user, and therefore, they do not expire. 
A new source MAC address that appears in a frame arriving at the device is added 
to the Dynamic Address table. This MAC address is retained for a configurable 
period of time. If another frame with the same source MAC address does not 
arrive at the device before that time period expires, the MAC entry is aged 
(deleted) from the table.
When a frame arrives at the device, the device searches for a corresponding/
matching destination MAC address entry in the static or dynamic table. If a match 
is found, the frame is marked for egress on a the port specified in the table. If 
frames are sent to a MAC address that is not found in the tables, they are 
transmitted/broadcasted to all the ports on the relevant VLAN. Such frames are 
referred to as unknown Unicast frames.
The device supports a maximum of 8K static and dynamic MAC addresses. 
						

							Managing MAC Address Tables
Configuring Static MAC Addresses
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Configuring Static MAC Addresses
Static MAC addresses are assigned to a specific physical interface and VLAN on 
the device. If that address is detected on another interface, it is ignored, and is not 
written to the address table.
To define a static address:
STEP 1Click MAC Address Tables > Static Addresses.
The Static Addresses page
 contains the currently defined static addresses.
STEP  2Click Add.
STEP  3Enter the parameters.
•VLAN ID—Select the VLAN ID for the port.
•MAC Address—Enter the interface MAC address.
•Interface—Select an interface (port, or LAG) for the entry.
•Status—Select how the entry is treated. The options are:
-Permanent—The system never removes this MAC address. If the static 
MAC address is saved in the Startup Configuration, it is retained after 
rebooting.
-Delete on reset—The static MAC address is deleted when the device is 
reset .
-Delete on timeout—The MAC address is deleted when aging occurs. 
-Secure—The MAC address is secure when the interface is in classic 
locked mode (see Configuring Port Security).
STEP  4Click Apply. A new entry appears in the table. 
						

							Managing MAC Address Tables
Managing Dynamic MAC Addresses
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Managing Dynamic MAC Addresses
The Dynamic Address Table (bridging table) contains the MAC addresses 
acquired by monitoring the source addresses of frames entering the device.
To prevent this table from overflowing and to make room for new MAC addresses, 
an address is deleted if no corresponding traffic is received for a certain period. 
This period of time is the aging interval.
Configuring Dynamic MAC Address Aging Time
To configure the aging interval for dynamic addresses:
STEP 1Click MAC Address Tables > Dynamic Address Settings.
STEP  2Enter Aging Time. The aging time is a value between the user-configured value 
and twice that value minus 1. For example, if you entered 300 seconds, the aging 
time is between 300 and 599 seconds. 
STEP  3Click Apply. The aging time is updated.
Querying Dynamic Addresses
To query dynamic addresses:
STEP 1Click MAC Address Tables > Dynamic Addresses.
STEP  2In the Filter block, you can enter the following query criteria:
•VLAN ID—Enter the VLAN ID for which the table is queried.
•MAC Address—Enter the MAC address for which the table is queried.
•Interface—Select the interface for which the table is queried. The query can 
search for specific unit/slot, ports, or LAGs.
STEP  3Enter the Dynamic Address Table Sort Key field by which the table is sorted. The 
address table can be sorted by VLAN ID, MAC address, or interface.
STEP  4Click Go. The Dynamic MAC Address Table is queried and the results are 
displayed.
To delete all of the dynamic MAC addresses. click Clear Table. 
						

							Managing MAC Address Tables
Defining Reserved MAC Addresses
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Defining Reserved MAC Addresses
When the device receives a frame with a Destination MAC address that belongs to 
a reserved range (per the IEEE standard), the frame can be discarded or bridged. 
The entry in the Reserved MAC Address Table can either specify the reserved 
MAC address or the reserved MAC address and a frame type:
To add an entry for a reserved MAC address:
STEP 1Click MAC Address Tables > Reserved MAC Addresses. The Reserved MAC 
Addresses page opens.
STEP  2Click Add.
STEP  3Enter the values for the following fields:
•MAC Address—Select the MAC address to be reserved.
•Frame Type—Select a frame type based on the following criteria:
-
Ethernet V2—Applies to Ethernet V2 packets with the specific MAC 
address.
-
LLC—Applies to Logical Link Control (LLC) packets with the specific 
MAC address.
-
LLC-SNAP—Applies to Logical Link Control/Sub-Network Access 
Protocol (LLC-SNAP) packets with the specific MAC address.
-
All—Applies to all packets with the specific MAC address.
•Action—Select one of the following actions to be taken upon receiving a 
packet that matches the selected criteria:
-
Discard—Delete the packet.
-
Bridge—Forward the packet to all VLAN members.
Click Apply. A new MAC address is reserved. 
						

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Multicast
This section describes the Multicast Forwarding feature, and covers the following 
topics:
•Multicast Forwarding
•Defining Multicast Properties
•Adding MAC Group Address
•Adding IP Multicast Group Addresses
•Configuring IGMP Snooping
•MLD Snooping
•Querying IGMP/MLD IP Multicast Group
•Defining Multicast Router Ports
•Defining Forward All Multicast
•Defining Unregistered Multicast Settings
Multicast Forwarding
Multicast forwarding enables one-to-many information dissemination. Multicast 
applications are useful for dissemination of information to multiple clients, where 
clients do not require reception of the entire content. A typical application is a 
cable-TV-like service, where clients can join a channel in the middle of a 
transmission, and leave before it ends.
The data is sent only to relevant ports. Forwarding the data only to the relevant 
ports conserves bandwidth and host resources on links. 
						

							Multicast
Multicast Forwarding
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For Multicast forwarding to work across IP subnets, nodes, and routers must be 
Multicast-capable. A Multicast-capable node must be able to:
•Send and receive Multicast packets.
•Register the Multicast addresses being listened to by the node with local 
routers, so that local and remote routers can route the Multicast packet to 
the nodes.
Typical Multicast Setup
While Multicast routers route Multicast packets between IP subnets, Multicast-
capable Layer 2 switches forward Multicast packets to registered nodes within a 
LAN or VLAN.
A typical setup involves a router that forwards the Multicast streams between 
private and/or public IP networks, a device with Internet Group Membership 
Protocol (IGMP) snooping capabilities, or Multicast Listener Discovery (MLD) 
snooping, and a Multicast client that wants to receive a Multicast stream. In this 
setup, the router sends IGMP queries periodically. 
NOTEMLD for IPv6 is derived from the IGMP v2 for IPv4. Even though the description in 
this section is mostly for IGMP, it also describes coverage of MLD where implied. 
These queries reach the device, which in turn floods the queries to the VLAN, and 
also learns the port where there is a Multicast router (Mrouter). When a host 
receives the IGMP query message, it responds with an IGMP Join message saying 
that the host wants to receive a specific Multicast stream and optionally from a 
specific source. The device with the IGMP snooping analyzes the Join messages, 
and learns that the Multicast stream the host has requested must be forwarded to 
this specific port. It then forwards the IGMP Join to the Mrouter only. Similarly, 
when the Mrouter receives an IGMP Join message, it learns the interface from 
which it received the Join messages that wants to receive a specific Multicast 
stream. The Mrouter forwards the requested Multicast stream to the interface.
In a Layer 2 Multicast service, a Layer 2 switch receives a single frame addressed 
to a specific Multicast address. It creates copies of the frame to be transmitted on 
each relevant port. 
When the device is IGMP/MLD-snooping-enabled and receives a frame for a 
Multicast stream, it forwards the Multicast frame to all the ports that have 
registered to receive the Multicast stream using IGMP Join messages. 
						

							Multicast
Multicast Forwarding
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The device can forward Multicast streams based on one of the following options: 
•Multicast MAC Group Address
•IP Multicast Group Address (G) 
•A combination of the source IP address (S) and the destination IP Multicast 
Group Address (G) of the Multicast packet. 
One of these options can be configured per VLAN. 
The system maintains lists of Multicast groups for each VLAN, and this manages 
the Multicast information that each port should receive. The Multicast groups and 
their receiving ports can be configured statically or learned dynamically using 
IGMP or Multicast Listener Discovery (MLD) protocols snooping.
Multicast registration is the process of listening and responding to Multicast 
registration protocols. The available protocols are IGMP for IPv4 and MLD for IPv6.
When IGMP/MLD snooping is enabled in a device on a VLAN, it analyzes the IGMP/
MLD packets it receives from the VLAN connected to the device and Multicast 
routers in the network. 
When a device learns that a host is using IGMP/MLD messages to register to 
receive a Multicast stream, optionally from a specific source, the device adds the 
registration to its Multicast Forwarding Data Base (MFDB).
IGMP/MLD snooping can effectively reduce Multicast traffic from streaming 
bandwidth-intensive IP applications. A device using IGMP/MLD snooping only 
forwards Multicast traffic to the hosts interested in that traffic. This reduction of 
Multicast traffic reduces the packet processing at the device, and also reduces 
the workload of the end hosts, since they do not have to receive and filter all of the 
Multicast traffic generated in the network.
The following versions are supported:
•IGMP v1/v2/ v3 
•MLD v1/v2
•A simple IGMP Snooping Querier
An IGMP Querier is required to facilitate the IGMP protocol on a given subnet. In 
general, a Multicast router is also an IGMP Querier. When there are multiple IGMP 
Queriers in a subnet, the queriers elect a single querier as the primary querier. 
The device can be configured to be an IGMP Querier as a backup querier, or in 
situation where a regular IGMP Querier does not exist. The device is not a full 
capability IGMP Querier.  
						

							Multicast
Defining Multicast Properties
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If the device is enabled as an IGMP Querier, it star ts after 60 seconds have passed 
with no IGMP traffic (queries) detected from a Multicast router. In the presence of 
other IGMP Queriers, the device might (or might not) stop sending queries, based 
on the results of the standard querier selection process.
Multicast Address Properties
Multicast addresses have the following properties:
•Each IPv4 Multicast address is in the address range 224.0.0.0 to 
239.255.255.255. 
•The IPv6 Multicast address is FF00:/8.
•To map an IP Multicast group address to an Layer 2 Multicast address:
-For IPv4, this is mapped by taking the 23 low-order bits from the IPv4 
address, and adding them to the 01:00:5e prefix. By standard, the upper 
nine bits of the IP address are ignored, and any IP addresses that only 
differ in the value of these upper bits are mapped to the same Layer 2 
address, since the lower 23 bits that are used are identical. For example, 
234.129.2.3 is mapped to a MAC Multicast group address 
01:00:5e:01:02:03. Up to 32 IP Multicast group addresses can be 
mapped to the same Layer 2 address.
-For IPv6, this is mapped by taking the 32 low-order bits of the Multicast 
address, and adding the prefix of 33:33. For example, the IPv6 Multicast 
address FF00:1122:3344 is mapped to Layer 2 Multicast 
33:33:11:22:33:44.
Defining Multicast Properties
The Properties page enables you to configure the Bridge Multicast filtering status.
By default, all Multicast frames are flooded to all ports of the VLAN. To selectively 
forward only to relevant ports and filter (drop) the Multicast on the rest of the ports, 
enable Bridge Multicast filtering status in the Properties page.
If filtering is enabled, Multicast frames are forwarded to a subset of the ports in the 
relevant VLAN as defined in the Multicast Forwarding Data Base. Multicast filtering 
is enforced on all traffic. By default, such traffic is flooded to all relevant ports, but 
you can limit forwarding to a smaller subset. 
						

							Multicast
Defining Multicast Properties
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A common way of representing Multicast membership is the (S,G) notation where 
S is the (single) source sending a Multicast stream of data, and G is the IPv4 or IPv6 
group address. If a Multicast client can receive Multicast traffic from any source of 
a specific Multicast group, this is saved as (*,G).
The following are ways of forwarding Multicast frames:
•MAC Group Address—Based on the destination MAC address in the 
Ethernet frame. 
NOTEAs mentioned before, one or more IP Multicast group addresses 
can be mapped to a MAC group address. Forwarding, based on the MAC 
group address, can result in an IP Multicast stream being forwarded to 
ports that have no receiver for the stream.
•IP Group Address—Based on the destination IP address of the IP packet 
(*,G).
•Source Specific IP Group Address—Based on both the destination IP 
address and the source IP address of the IP packet (S,G).
By selecting the forwarding mode, you can define the method used by hardware 
to identify Multicast flow by one of the following options: MAC Group Address, IP 
Group Address, or Source Specific IP Group Address.
(S,G) is supported by IGMPv3 and MLDv2, while IGMPv1/2 and MLDv1 support 
only (*.G), which is just the group ID.
The device supports a maximum of 256 static and dynamic Multicast group 
addresses. 
To enable Multicast filtering, and select the forwarding method: 
STEP 1Click Multicast > Properties.
STEP  2Enter the parameters.
•Bridge Multicast Filtering Status—Select to enable filtering. 
•VLAN ID—Select the VLAN ID to set its forwarding method.
•Forwarding Method for IPv6—Set one of the following forwarding 
methods for IPv6 addresses: MAC Group Address, IP Group Address, or 
Source Specific IP Group Address.
•Forwarding Method for IPv4—Set one of the following forwarding 
methods for IPv4 addresses: MAC Group Address, IP Group Address, or 
Source Specific IP Group Address. 
						

							Multicast
Adding MAC Group Address
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STEP  3Click Apply. The Running Configuration file is updated.
Adding MAC Group Address
The device supports forwarding incoming Multicast traffic based on the Multicast 
group information. This information is derived from the IGMP/MLD packets 
received or as the result of manual configuration, and it is stored in the Multicast 
For warding Database (MFDB) .
When a frame is received from a VLAN that is configured to forward Multicast 
streams, based on MAC group addresses, and its destination address is a Layer 2 
Multicast address, the frame is forwarded to all ports that are members of the 
MAC group address.
The MAC Group Address page
 has the following functions:
•Query and view information from the MFDB, relating to a specific VLAN ID or 
a specific MAC address group. This data is acquired either dynamically 
through IGMP/MLD snooping or statically by manual entry.
•Add or delete static entries to the MFDB that provide static forwarding 
information, based on MAC destination addresses.
•Display a list of all ports/LAGs that are a member of each VLAN ID and MAC 
address group, and enter whether traffic is forwarded to it or not.
For viewing the forwarding information when the mode is IP Address Group or IP 
and Source Group, use the IP Multicast Group Address page.
To define and view MAC Multicast groups:
STEP 1Click Multicast > MAC Group Address.
STEP  2Enter the parameters.
•VLAN ID Equals To—Set the VLAN ID of the group to be displayed.
•MAC Group Address Equals To—Set the MAC address of the Multicast 
group to be displayed. If no MAC Group Address is specified, the page 
contains all the MAC Group Addresses from the selected VLAN.
STEP  3Click Go, and the MAC Multicast group addresses are displayed in the lower 
block.