Owner's Manual

Chapter 20. IPv4 Unicast Routing | 599
NETGEAR 8800 User Manual
Note: Using route sharing makes router troubleshooting more difficult
because of the complexity in predicting the path over which the
traffic travels.
Compressed Routes
Compressed routes allow you to reduce the number of routes that are installed in the
hardware routing tables. The switch uses hardware routing tables to improve packet
forwarding performance. The switch can use both hardware and software to forward packets,
but packet forwarding without software processing is faster. The hardware routing tables
have less storage space than the software, so compressed routes conserve resources and
improve scaling
The compressed route feature allows you to install less specific routes in the table, when
overlapping routes with same nexthop exist. This route pruning technique is implemented as
part of the Route Manager (RtMgr) process.
When a route is added, deleted or updated, the pruning algorithm is applied to see if the new
route and/or its immediate children can be compressed or uncompressed as follows:
• If the parent node (immediate less specific route) of the newly added IP prefix has the
same gateway as the new IP prefix, the newly added prefix is compressed.
• If the gateways of the newly added IP prefix and its immediate children are the same, the
child nodes are compressed.
• If the gateways of the newly added IP prefix and its immediate children are not the same,
and the child nodes had been previously compressed, the child nodes are
uncompressed.
Event Log Messages
Event log messages are given in the following circumstances:
• When compression or uncompression start and end.
[ Severity level: Debug -Summary ]
• During each chunking start and end
[ Severity level: Debug -Verbose ]
• When a route is compressed or uncompressed.
[ Severity level: Debug -Verbose ]
Exceptional Scenarios
This section explains instances of exceptional route compression behavior.
• When a node does not have any best route.
Consider the routing table shown in Table 58. When a node does not have any best
route, children are uncompressed, if they were already compressed. Also this node is
uncompressed, if it had previously been compressed.