3Com Switch 7750 Configuration Guide

Common Multicast Configuration Tasks 443
to the forwarding entry. If the packet is not received on the right ingress of the
forwarding entry, the packet is regarded as a wrongif packet. The wrongif packet
will be reported to the CPU for processing.
In some network, many wrongif packets will be reported to the CPU of the switch
for processing, thus aggravating the workload of the switch. In this case, you can
configure suppression on the holdtime of wrongif packets, so that the wrongif
packets will be dropped instead of being forwarded to the CPU of the switch for
processing, and the CPU will be prevented from being stricken by too many
packets.
c
CAUTION:
■ During the configuration, if the seconds argument is less than 15, the system
sets the holdtime to 15; if the seconds argument is more than 15, the system
sets the holdtime to the multiples of 15 according to the user-defined range.
For example, if you set the seconds argument to 14, the system sets the
holdtime to 15; if you set the seconds argument to 16, the system sets the
holdtime to 30; if you set the seconds argument to 31, the system sets the
holdtime to 45, and so on.
■ When the holdtime is set to 0, the report of CPU packets to the CPU is not
suppressed.
Configuring Static
Router Ports
In a ring network or a network with double uplinks, users usually configure both
primary and secondary links over a connection in order to avoid communication
interruption due to link failure. When the primary link fails, the secondary link can
replace it immediately to avoid communication interruption.
On a link where a multicast protocol (such as PIM or IGMP) is enabled, the switch
cannot restore multicast data transmission after switchover until the switch
receives multicast packets (such as PIM Hello packets and IGMP general group
query messages) and adds the static router port to the corresponding multicast
entry. The process will cause temporary interruption of multicast data
transmission. For real-time services such as IPTV, the delay will cause some
undesirable problems such as picture jitter.
You can configure a port as a static router port. When the link state switches, the
multicast data can be switched from the primary link to the secondary link
immediately, so that the switch need not wait for multicast protocol packets and
the multicast data transmission delay is avoided. Additionally, a static port never
times out except when a link fails or the configuration is removed.
Configure static router ports as follows:
Table 356 Configure suppression on the holdtime of multicast wrongif packets
Operation Command Description
Enter system view system-view -
Configure suppression on the
holdtime of multicast wrongif
packets
multicast wrongif-holdtime
seconds
Required
By default, the holdtime of
multicast wrongif packets is
15 seconds.