Configuration Guide User guide

BigIron RX Series Configuration Guide 213
53-1002484-04
Configuring forwarding parameters
7
Table 53 lists the default and configurable maximum numbers of paths for each IP route source
that can provide equal-cost paths to the IP route table. The table also lists where to find
configuration information for the route source’s load sharing parameters.
The load sharing state for all the route sources is based on the state of IP load sharing. Since IP
load sharing is enabled by default on the device, load sharing for static IP routes, RIP routes, OSPF
routes, and BGP4 routes also is enabled by default.
How IP load sharing works
On the device, IP load sharing (also known as ECMP load sharing) is done by the hardware. If there
is more than one path to a given destination, a hash is calculated based on the source MAC
address, destination MAC address, source IP address, destination IP address, and IP protocol. This
hash is used to select one of the paths.
Changing the maximum number of load sharing paths
By default, IP load sharing allows IP traffic to be balanced across up to four equal path. You can
change the maximum number of paths that the device supports to a value of 2 – 8.
For optimal results, set the maximum number of paths to a value equal to or greater than the
maximum number of equal-cost paths that your network typically contains. For example, if the
device has six next-hop routers, set the maximum paths value to six.
NOTE
If the setting for the maximum number of paths is lower than the actual number of equal-cost paths,
the software does not use all the paths for load sharing.
To change the number of paths, enter a command such as the following.
BigIron RX(config)# ip load-sharing 8
Syntax: [no] ip load-sharing [<number>]
Enter a value from 2 – 8 for <number> to set the maximum number of paths.
TABLE 53 Default load sharing parameters for route sources
Route source Default maximum number of paths Maximum number of paths See...
Static IP route 4
NOTE: This value depends on the
value for IP load sharing,
and is not separately
configurable.
8
NOTE: This value depends
on the value for IP
load sharing, and is
not separately
configurable.
page 213
RIP 4
NOTE: This value depends on the
value for IP load sharing,
and is not separately
configurable.
8
NOTE: This value depends
on the value for IP
load sharing, and is
not separately
configurable.
page 213
OSPF 4 8 page 213
BGP4 1 4 page 867