Huawei S6700 Series Configuration Manual page 259

S6700 Series Ethernet Switches
Configuration Guide - IP Routing
It is easier to identify and memorize the host name than the system ID. After this function is
configured, the host name will displays when display command is used.
IS-IS Route Summarization
Route summarization is a function for summarizing routes with the same IP prefix into one route.
On a large-scale IS-IS network, you can configure route summarization to reduce the number
of IS-IS routes in the routing table. This improve the usage of system resources and facilitates
route management.
IP network segments are not affected when a link frequently alternates between Up and Down
on an IP network segment. This prevents route flapping and improves the network stability.
The switch supports classless network-based route summarization.
IS-IS Load Balancing
If there are redundant links on an IS-IS network, there may be multiple equal-cost routes.
Configuring IS-IS load balancing can evenly distribute traffic to each link. This increases the
bandwidth usage of each link and prevents network congestion caused by some overloaded links.
IS-IS load balancing, however, may affect traffic management because traffic will be randomly
forwarded in this mode.
IS-IS Preference
If there are redundant links on an IS-IS network, there may be multiple equal-cost routes.
The switch allows you to configure preference values for equal-cost IS-IS routes so that only
the route with the highest preference will be used and the others will function as backups.
This facilitates traffic management, improves the network reliability, and avoids configuration
change.
IS-IS Fast Convergence
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Issue 01 (2012-03-15)
Incremental SPF (I-SPF)
I-SPF calculates only changed routes at a time, but not all routes.
ISO-10589 defines Dijkstra as the algorithm to calculate routes. When a node is added to
or removed from a network topology, all routes of all nodes need to be calculated if the
Dijkstra algorithm is adopted. As a result, it takes a long time and occupies excessive
resources, reducing the route convergence speed of the entire network.
I-SPF improves this algorithm. Except for the first time, only changed nodes instead of all
nodes are involved in calculation. The SPT generated at last is the same as that generated
by the Dijkstra algorithm. This decreases the CPU usage and speeds up route convergence.
Partial route calculation (PRC)
Similar to I-SPF, only changed nodes are involved in PRC. PRC, however, does not
calculate the shortest path but updates leaf routes based on the SPT calculated by I-SPF.
In route calculation, a leaf represents a route, and a node represents a switch. If the SPT
calculated using I-SPF changes, PRC calculates all the leaves on only the changed node;
if the SPT calculated using I-SPF does not change, PRC calculates only the changed leaf.
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