Detecting Multicast Routers
Local Management Supplement
A-3
There are many multicast routing protocols that the switch supports.
These include the following:
•
PIM version 1 and 2
•
CBT (core based trees)
•
MOSPF
•
DVMRP
The routing protocols are detected as follows:
•
All the multicast routing protocols have a destination address of
01-00-5E.
•
DVMRP and PIM version 1 run over IGMP. If the IGMP frame type is
not a REPORT, QUERY, OR LEAVE, then the frame is assumed to be
one of these.
•
PIM version 2 is IP protocol type 0x67.
•
OSPF is IP protocol type 0x59. To detect that the frame is a multicast
OSPF (MOSPF), the OSPF data must be looked at. The data starts
after the IP header. Byte 31 (options) needs to be checked. If bit 2 is
set (0x02 the MC bit), the frame is a MOSPF frame.
•
CBT is IP protocol type 0x07.
•
IGMP frames are detected by checking the IP protocol type. If the type
is -x02, it is IGMP. The first byte following the IP header is the IGMP
frame type and version. (Note that the lower 4 bits of the first byte in
the IP header is the length of the IP header in 32 bit words.) The
version is always 1, so the entire byte (vtype) may be used to
check the IGMP type as follows:
•
0x11 = query
•
0x12 = report version 1
•
0x16 = report version 2
•
0x17 = leave
