Cabletron Systems SmartSwitch 8-slot, Руководство пользователя

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Chapter 7: Multicast Routing Configuration Guide
7 - 2 SSR User Reference Manual
• Pruning, which is an operation DVMRP routers perform to exclude interfaces not in
the shortest path tree.
DVMRP uses the Reverse Path Multicasting (RPM) algorithm to perform pruning.In
RPM, a source network rather than a host is paired with a multicast group. RPM per-
mits the SSR to maintain multiple multicast groups.
On the SSR, DVMRP can be configured on a per-interface basis. An interface does not
have to run both DVMRP and IGMP. You can start and stop DVMRP independently
from other routing protocols. IGMP starts and stops automatically with DVMRP.
To support backward compatibility on DVMRP interfaces, you can configure the rout-
er expire time and prune time on each SSR DVMRP interface. This lets it work with
older versions of DVMRP.
You can use threshold values and scopes to control internetwork traffic on each DVM-
RP interface. Threshold values determine whether traffic is either restricted or not re-
stricted to a subnet, site, or region. Scopes define a set of multicast addresses of devices
to which the SSR can send DVMRP data. Scopes can include only addresses of devices
on a company's internal network and cannot include addresses that require the SSR to
send DVMRP data on the internet.
You can also configure tunnels on SSR DVMRP interfaces. A tunnel is used to send
packets between routers separated by gateways that do not support multicast routing.
A tunnel acts as a virtual network between two routers running DVMRP. A tunnel does
not run IGMP.
Configure IGMP
You configure IGMP on the SSR by performing the following configuration tasks.
• Creating IP interfaces.
• Setting global parameters that will be used for all the interfaces on which DVMRP
is enabled.
• Configuring IGMP on individual interfaces. You do so by enabling and disabling
IGMP on interfaces and then setting IGMP parameters on the interfaces on which
IGMP is enabled.
Configuring IGMP on an IP Interface
By default IGMP is disabled on the SSR.