Accton Technology ES4626 - Manual (Page 647)

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become the specified transmitter of the sub-network. If some have the same distance,
then the one with the lowest IP prevails.
After some interface of the switch is configured to Function DVMRP Protocol, the
switch will multicast Probe message to other DVMRP switches on this interface, which is
used to find neighbors and detect the capabilities of each other. If no Probe message
from the neighbor is received until the neighbor is timed out, then this neighbor is
considered missing.
In DVMRP, source network routing selection message are exchanged in a basic
manner same to RIP. That is, routing report message is transmitted among DVMRP
neighbors periodically (the default is 60 seconds). The routing information in DVMRP
routing selection table is used to set up source distribution tree, i.e. to determine by
which neighbor it passes to get to the source transmitting multicast packet; the interface
to this neighbor is called upstream interface. The routing report includes source network
(use net mask) address and the hop entry for routing scale.
In order to finish transmission correctly, every DVMRP switch needs to know which
downstream switches need to receive multicast packet from some specific source
network through it. After receiving packets from some specific source, DVMRP switch
firstly will broadcast these multicast packets from all downstream interfaces, i.e. the
interfaces on which there are other DVMRP switches which have dependence on the
specific source. After receiving Prune message from some downstream switch on the
interface, it will prune this switch. DVMRP switch makes use of poison reverse to notify
the upstream switch for some specific source: “I am your downstream.” By adding infinity
(32) to the routing distance of some specific source it broadcasts, DVMRP switch
responds to the source upstream exchange to fulfill poison reverse. This means distance
correct value is 1 to 2* infinity (32) -1 or 1 to 63, 1 to 63 means it can get to source
network, 32 means source network is not arrival, 33 to 63 means the switch which
generates the report message will receive multicast packets from specific source
depending on upstream router.
16.4.2 Configuration Task List
1、 Globally enable and disable DVMRP (required)
2、 Configure Enable and Disable DVMRP Protocol at the interface (optional)
3、 Configure DVMRP Sub-parameters (optional)
Configure DVMRP interface parameters
1）Configure the delay of transmitting report message on DVMRP interface and the
message number each time it transmits.
2）Configure metric value of DVMRP interface
3）Configure if DVMRP is able to set up neighbors with DVMRP routers which can not