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Multicast Tunnels View


Use the Multicast Tunnels View to manage multicast tunnels and DVMRP operations on an GIGAswitch/IP or IP Switch Gateway.

To present the Multicast Tunnels View, click the Multicast Tunnels link in the Config Tool main menu.

If there are currently no multicast tunnels, this view presents only a field in which to enter the IP address of a new tunnel. The following figure shows an example.

If tunnels have been created, a list of existing tunnels is presented. The following figure shows an example of this view.



The following section describes the fields in the Multicast Tunnels View. Note that a value for the Local Address field is mandatory. You can use the default values for all other parameters; they are reasonable for a large number of environments.

IP Address
Identifies the IP address of the remote end of the multicast tunnel interface. The remote multicast router must support the IP-in-IP DVMRP tunnel encapsulation. The remote multicast router must also be configured with a tunnel interface to the local router.
Threshold
Represents the minimum IP time to live (TTL) required for a multicast datagram to be forwarded. It is used to administratively control the scope of multicast datagrams. Note that the TTL of forwarded packets is only compared to the threshold, not decremented by the threshold. Every multicast router decrements the TTL by 1. When connecting to the Internet Multicast Backbone (MBONE) the following values are recommended:

TTL

Interface Type

1

Link within a site

32

Site boundary

64

Regional boundary

128

Continental boundary


The default value is 1. In a typical configuration, the Threshold parameter should be set identically at both ends to avoid asymmetric paths.
Rate Limit
Specifies a bandwidth limit for all multicast traffic forwarded along the tunnel. This provides a constraint on the amount of wide-area transit resources that multicast traffic can consume. The rate limit value is specified in units of kilobits per second.

[Note] This feature is not supported in the current DIGITAL release.


The default value is 0, which represents the special case of no rate limit. In a typical configuration, the Rate Limit parameter should be set identically at both ends to avoid asymmetric paths.
Metric
Represents the cost associated with sending a datagram on the interface. It may be used to influence the choice of routes. A less expensive interface (smaller metric) will be preferred to a more expensive interface (larger metric). Note that metrics should be kept as small as possible, DVMRP cannot route along a path with a sum of metrics greater than 31. The default value is 1. In a typical configuration, the Metric parameter should be set identically at both ends to avoid asymmetric paths.
Local Address
Specifies the IP address of the local interface that is the multicast tunnel's source. This address must be specified and it must be an actual interface address on the local system. The remote multicast router must also be configured with a tunnel interface that specifies this address as the tunnel destination address.

The tunnel becomes available for routing as soon as both the Destination and the Local IP Address have been committed.

See also:
Multicast Tunnel Configuration

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