3Com 4007, Implementation Manual, Page: 441 / 684

Configuring DVMRP Tunnels 441
Table 79 lists conventional numeric values and network objectives.
Configuring DVMRP
Tunnels
A DVMRP tunnel allows IP multicast packets to traverse a portion of your
network infrastructure that is not multicast-aware. In Multilayer
Switching Modules, you can define tunnels, modify tunnel characteristics,
display information about tunnels you have defined, and remove tunnels.
Important
Considerations
■
All networks do not require DVMRP tunnels. A network needs a
tunnel only if IP multicast packets must go through one or more
unicast routers to reach IP multicast group members.
■
You can configure any routing interface on a Multilayer Switching
Module to be a DVMRP tunnel end point. The other tunnel end point
must be a multicast interface on a different system and subnetwork.
■
Before you can define a tunnel end point, you must configure a
routing interface and enable DVMRP on the interface. Think of a
tunnel end point as being layered on top of an existing IP multicast
routing interface.
■
The maximum number of IP multicast tunnels that you can define on a
Switch 4007 Multilayer Switching Module is 8.
■
To define a tunnel, you specify the following tunnel characteristics:
■
The index number of the local router interface that serves as the
tunnel end point.
■
The IP address of the destination multicast router. This address
must be a remote address
. The destination multicast router cannot
be directly connected to the same subnetwork.
■
When you define a tunnel, the module assigns tunnel metric and
tunnel TTL threshold values of 1. You can modify these at any time.
Table 79 Conventional TTL Scope Control Values
TTL Value Objective
0 Restricted to the same host
1 Restricted to the same subnetwork
16 Restricted to the same site
64 Restricted to the same region
128 Restricted to the same continent
255 Unrestricted in scope