D-Link TM DES-6500, Руководство пользователя

Страница: 180 / 353

xStack DES-6500 Modular Layer 3 Chassis Ethernet Switch User Manual
Max Response Time Sets the maximum amount of time allowed before sending an IGMP response report. A
value between 1 and 25 seconds can be entered, with a default of 10 seconds.
Robustness Variable A tuning variable to allow for subnetworks that are expected to lose a large number of
packets. A value between 2 and 255 can be entered, with larger values being specified for
subnetworks that are expected to lose larger numbers of packets.
Last Member Query
Interval Specifies the maximum amount of time between group-specific query messages, including
those sent in response to leave group messages. A value between 1 and 25. The default is
1
second.
State This field can be toggled between Enabled and Disabled and enables or disables IGMP for
the IP interface. The default is Disabled .
Click Apply to implement changes made.
DVMRP Interface Configuration
The Distance Vector Multicast Routing Protocol ( DVMRP ) is a hop-based method of building multicast delivery trees from
multicast sources to all nodes of a network. Because the delivery trees are ‘pruned’ and ‘shortest path’, DVMRP is relatively
efficient. Because multicast group membership information is forwarded by a distance-vector algorithm, propagation is slow.
DVMRP is optimized for high delay (high latency) relatively low bandwidth networks, and can be considered as a ‘best-effort’
multicasting protocol.
DVMRP resembles the Routing Information Protocol (RIP), but is extended for multicast delivery. DVMRP builds a routing table
to calculate ‘shortest paths’ back to the source of a multicast message, but defines a ‘route cost’ (similar to the hop count in RIP)
as a relative number that represents the real cost of using this route in the construction of a multicast delivery tree to be ‘pruned’ -
once the delivery tree has been established.
When a sender initiates a multicast, DVMRP initially assumes that all users on the network will want to receive the multicast
message. When an adjacent router receives the message, it checks its unicast routing table to determine the interface that gives the
shortest path (lowest cost) back to the source. If the multicast was received over the shortest path, then the adjacent router enters
the information into its tables and forwards the message. If the message is not received on the shortest path back to the source, the
message is dropped.
Route cost is a relative number that is used by DVMRP to calculate which branches of a multicast delivery tree should be
‘pruned’. The ‘cost’ is relative to other costs assigned to other DVMRP routes throughout the network.
The higher the route cost, the lower the probability that the current route will be chosen to be an active branch of the multicast
delivery tree (not ‘pruned’) - if there is an alternative route.
DVMRP Configuration
To enable DVMRP globally on the Switch, click Configuration > Layer 3 IP Networking > IP Multicast Routing Protocol >
Configuration . This will give the user access to the following screen:
Figure 6- 147. DVMRP Global Settings window
Use the pull down menu, choose Enabled , and click Apply to implement the DVMRP function on the Switch.
DVMRP Interface Settings
To view the DVMRP Interface Table , click Configuration > Layer 3 IP Networking > IP Multicast Routing Protocol >
DVMRP Interface Settings . This menu allows the Distance-Vector Multicast Routing Protocol (DVMRP) to be configured
for each IP interface defined on the Switch. Each IP interface configured on the Switch is displayed in the below DVMRP
Interface Configuration dialog box. To configure DVMRP for a particular interface, click the corresponding hyperlink for that
IP interface. This will open the DVMRP Interface Settings window:
165