Routing Multicast Traffic
367
F I G U R E 9 . 1 6
DVMRP tunnels
Multicast Open Shortest Path First (MOSPF)
Now we will concentrate on Multicast Open Shortest Path First (MOSPF),
which is a link state protocol. OSPFv2 includes some changes to allow mul-
ticast to be enabled on OSPF-enabled routers. This eliminates the need for
tunnels like those used for DVMRP.
To completely understand the full functionality of MOSPF, you must
have a good understanding of OSPF itself. However, here we will attempt to
cover only the basic functionality of MOSPF, so you should be fine with just
a basic understanding of OSPF.
For more on the OSPF, see CCNP: Advanced Cisco Router Configuration by
Todd Lammle, Kevin Hales, and Don Porter (Sybex, 1999).
MOSPF's basic functionality lies within a single OSPF area. Things get
more complicated as you route multicast traffic to other areas (inter-area
routing) or to other autonomous systems (inter-AS routing). This additional
complication requires more knowledge of OSPF routing. We will briefly dis-
cuss how this is accomplished in MOSPF, but most detail will be given
regarding MOSPF intra-area routing.
HostA
HostB HostC
HostD HostE
Source for
224.2.125.125
Members of group
224.2.125.125
172.16.1.10
E0
E0
S0
S0
S2
S1
S0
T0
T0
T1
T0
Router1
Router3
Router4
DVMRP Tunnel
DVMRP Tunnel
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