User Manual

Enterasys X-Pedition User Reference Manual 277
DVMRP Overview
TTL < 64 Threshold = 64 Application restricted to a region
TTL < 128 Threshold = 128 Application restricted to a continent
TTL = 255 Application not restricted
To configure the TTL Threshold, enter the following command in Configure mode:
TTL thresholding is not always considered useful. There is another approach of a range of multicast
addresses for “administrative” scoping. In other words, such addresses would be usable within a
certain administrative scope, a corporate network, for instance, but would not be forwarded across
the internet. The range from 239.0.0.0 through 239.255.255.255 is being reserved for
administratively scoped applications. Any organization can currently assign this range of addresses
and the packets will not be sent out of the organization. In addition, multiple scopes can be defined
on per-interface basis.
To prevent the XP from forwarding any data destined to a scoped group on an interface, enter the
following command in the Configure mode:
DVMRP Tunnels
The XP supports DVMRP tunnels to the MBONE (the multicast backbone of the Internet). You can
configure a DVMRP tunnel on a router if the other end is running DVMRP. The XP then sends and
receives multicast packets over the tunnel. Tunnels are CPU-intensive; they are not switched
directly through the XP’s multitasking ASICs.
DVMRP tunnels need to be created before being enabled. Tunnels are recognized by the tunnel
name. Once a DVMRP tunnel is created, you can enable DVMRP on the interface. The XP
supports a maximum of eight tunnels.
To configure a DVMRP tunnel, enter the following command in Configure mode:
You can also control the rate of DVMRP traffic in a DVMRP tunnel. The default rate is 500 Kbps.
To control the rate of DVMRP traffic, enter the following command in Configure mode:
Configure the TTL Threshold.
dvmrp set interface <ip-addr> threshold <number>
Configure the DVMRP scope. dvmrp set interface <ip-addr> scope
<ip-addr/mask>
Configure a DVMRP tunnel to MBONE. dvmrp create tunnel <string> local
<ip-addr> remote <ip-addr>
Configure the rate in a DVMRP tunnel.
dvmrp set interface <ip-addr> rate <number>