Ttl In Ip Multicast Packets; Multicast Mac Filtering - Avaya 8800 Planning And Engineering, Network Design

TTL in IP multicast packets

The Avaya Ethernet Routing Switch 8800/8600 treats multicast data packets with a Time To Live
(TTL) of 1 as expired packets and sends them to the CPU before dropping them. To avoid this,
ensure that the originating application uses a hop count large enough to enable the multicast stream
to traverse the network and reach all destinations without reaching a TTL of 1. Avaya recommends
using a TTL value of 33 or 34 to minimize the effect of looping in an unstable network.
To avoid sending packets with a TTL of 1 to the CPU, the switch prunes multicast streams with a
TTL of 1 if they generate a high load on the CPU. In addition, the switch prunes all multicast streams
with a TTL of 1 to the same group for sources on the same originating subnet as the stream.
To ensure that a switch does not receive multicast streams with a TTL of 1, thus pruning other
streams that originate from the same subnet for the same group, you can configure the upstream
Ethernet Routing Switch 8800/8600 (Switch 1) to drop multicast traffic with a TTL of less than 2 (see
Figure 85: IP multicast traffic with low TTL
egress the switch (Switch 1) with a TTL of 1 are dropped.
Figure 85: IP multicast traffic with low TTL
A change in the accepted egress TTL value does not take effect dynamically on active streams. To
change the TTL, disable DVMRP and then enable it again on the interface with a TTL of greater
than 2. Use this workaround for an Ethernet Routing Switch 8800/8600 network that has a high
number of multicast applications with no control on the hop count used by these applications.
In all cases, an application should not send multicast data with a TTL lower than 2. Otherwise, all of
that application traffic is dropped, and the load on the switch is increased. Enhanced modules (E, M,
or R series modules), which provide egress mirroring, do not experience this behavior.

Multicast MAC filtering

Certain network applications, such as the Microsoft Network Load Balancing Solution, require
multiple hosts to share a multicast MAC address. Instead of flooding all ports in the VLAN with this
June 2016
on page 185). In this configuration, all streams that
Planning and Engineering — Network Design
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General multicast considerations
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