Information Technology Reference
In-Depth Information
send RP-discovery messages to the rest of the PIM-SM routers in the internetwork with
the selected RP-to-group mappings.
PIMv2 Bootstrap Router
Instead of using auto-RP, you can configure a PIMv2 bootstrap router (BSR) to automati-
cally select an RP for the network. The RFC for PIM Version 2, RFC 2362, describes BSR.
With BSR, you configure BSR candidates (C-BSR) with priorities from 0 to 255 and a BSR
address. C-BSRs exchange bootstrap messages. Bootstrap messages are sent to multicast
IP 224.0.0.13 (all PIM routers). If a C-BSR receives a bootstrap message, it compares it
with its own. The largest priority C-BSR is selected as the BSR.
After the BSR is selected for the network, it collects a list of candidate RPs. The BSR se-
lects RP-to-group mappings, which is called the RP set, and distributes the selected RPs
using bootstrap messages sent to 224.0.0.13 (all PIM routers).
DVMRP
RFC 1075 describes DVMRP. It is the primary multicast routing protocol used in the mul-
ticast backbone (MBONE). The MBONE is used in the research community.
DVMRP operates in dense mode using RPF by hav ing routers send a copy of a multic ast
packet out all paths. Routers that receive the multicast packets then send prune messages
back to their upstream neighbor router to stop a data stream if no downstream receivers of
the multicast group exist (either receiving routers or hosts on connected segments).
DVMRP implements its ow n unic ast routing protocol, similar to RIP, based on hop counts.
DVMRP has a 32 hop-count limit. DVMRP does not sc ale suboptimally. Cisco's suppor t
of DVMRP is partial; DVMRP networks are usually implemented on UNIX machines run-
ning the
mrouted
process. A DVMRP tunnel is typically used to connect to the MBONE
DVMRP net work.
IPv6 Multicast Addresses
IPv6 retains the use and function of multicast addresses as a major address class. IPv6 pre-
fix FF00::/8 is allocated for all IPv6 multicast addresses. IPv6 multicast addresses are de-
scribed in RFC 2373. EIGRP for IPv6, OSPFv3, and RIPng routing protocols use multicast
addresses to communicate between router neighbors.
The format of the IPv6 multicast address is described in Chapter 9, “Internet Protocol Ver-
sion 6.” The common multicast addresses are repeated in Table 11-11.
