3Com CoreBuilder 3500, Implementation Manual

Page: 348 / 592

348 C
HAPTER
13: IP M
ULTICAST
R
OUTING
6 View the various displays, routing table and cache to see how the system
is processing IP multicast traffic.
See “Viewing the DVMRP Routing Table” and “Viewing the DVMRP
Cache” later in this chapter.
7 Use the traceroute option for troubleshooting or to determine the traffic
paths.
See “Using IP Multicast Traceroute” later in this chapter.
Impact of Multicast
Limits
As described in Chapter 7, you can use the
bridge port
multicastLimit
option to set per-port multicast limits. This optional
feature can prevent segments of your network from being adversely
affected by multicast or broadcast storms. If network users have trouble
receiving IP multicast application traffic, verify that bridge ports are not
configured with a multicast limit that is too low.
Impact of IEEE 802.1Q
on Multicasts
Multicasting in 802.1Q VLAN tagging environments may have
performance implications for your system. Specifically, if you have
multiple VLANs associated with a single port, the system is forced to
replicate multicast packets to each VLAN that has multicast group
members, even if the path to reach the members is the same physical
link. To achieve wirespeed multicast performance, 3Com recommends
that you configure only one VLAN per port. Contact your 3Com
representative about network design options.
Protocol
Interoperability
Routing protocols other than DVMRP exist to support IP multicast
functions. Interoperability issues between these routing protocols require
that you plan your routing infrastructure carefully.