We saw in SEP topology change notification, we saw how the SEP protocol implements the SEP topology change notification, let's see now how to suppress it.
Topology changes of a SEP segment are advertised to other SEP segments or upper-layer networks. A large number of topology change (TC) notification packets are generated in the following cases:
A link becomes disconnected transiently.
A SEP segment is attacked by invalid TC notification packets.
A networking scenario has multiple SEP ring networks.
Figure 1 shows a networking scenario with three SEP ring networks. If the topology of SEP segment 3 changes, the number of TC notification packets doubles and SEP segment 2 is flooded with these packets. Each time TC notification packets pass through a SEP segment, the number of these TC notification packets doubles.
Figure 1 Networking diagram for multiple SEP ring networks
The sending of many TC notification packets reduces the CPU's capability in processing other types of packets. In addition, devices in the SEP segments are caused to frequently refresh MAC address entries and this consumes bandwidth resources. To solve such problems, the following measures can be taken to suppress TC notification packets:
Suppress TC notification packets based on their source addresses by configuring a device to process only one of the TC notification packets carrying the same source address.
Configure a device to process a specified number of TC notification packets within a specified time period. By default, three TC notification packets with different source addresses are processed in 2s.
Avoid the networking scenario that has more than three SEP ring networks.
