Intel Express 530T, Руководство пользователя

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C H A P T E R 2 Intel
®
Express 530T Switch Users Guide
20
GARP VLAN Registration Protocol
(GVRP)
Since IEEE 802.1Q VLANs can span networks, it poses a challenge for
network administrators to manage changes to the VLAN. The GARP
(Generic Attribute Registration Protocol) VLAN Registration Protocol
(GVRP) provides a dynamic mechanism for switches to share topology
information and manage changes with other switches. This alleviates the
network administrator from manually propagating VLAN configuration
information across switches.
GARP is defined by the IEEE 802.1D (1998 Edition) specification and
is the mechanism used by switches and end nodes to propagate VLAN
configurations across the network domain. GVRP uses GARP as a
foundation to propagate VLAN configurations to other switches.
Devices that support GVRP transmit their updates to a known multicast
address that all GVRP-capable devices monitor for information updates.
Sending GVRP messages between switches accomplishes these tasks:
• Dynamically adds or removes a port from participating in a VLAN
• Sends updates about the switch’s own VLAN configuration to
neighboring GVRP-capable devices
• Integrates dynamic and static VLAN configurations within the same
switch. Static VLAN configurations are created by the user on the
switch for devices that don’t support GVRP
Dynamically created VLANs are not saved in the switch’s memory.
When the device that is sending out the GVRP updates is disabled or
rebooted the dynamic VLAN is removed.
Internet Group Multicast Protocol
Under normal circumstances, multicast traffic is broadcast by the switch
to all ports. For multicast traffic based on the IGMP (Internet Group
Multicast Protocol), the switch can optimize the broadcasting of
multicast traffic by forwarding multicast traffic to only the ports that
require it.
IGMP snooping is a feature that allows the switch to forward multicast
traffic intelligently. The switch “snoops” the IGMP query and report
messages and forwards traffic to only the ports that request the multicast
traffic. This prevents the switch from broadcasting the traffic to all ports
and possibly affecting network performance.
IGMP requires a router that records the presence of multicast groups on
its subnets and keeps track of group membership. It is important to
remember that multicasting is not connection oriented, so data is
delivered to the requesting hosts on a best-effort level of service.
NOTE
The 530T supports a
maximum of 24 IGMP
sessions, with a maximum of
32 multicast groups per
session. These parameters are
the same whether the 530T is
standalone or in a stack.
530-Chapter2.fm Page 20 Monday, September 11, 2000 4:14 PM