Configuring route reflection parameters, How load sharing affects route selection – Brocade Multi-Service IronWare Routing Configuration Guide (Supporting R05.6.00) User Manual
Page 101
Multi-Service IronWare Routing Configuration Guide
73
53-1003033-02
Changing the maximum number of paths for BGP4 load sharing
Changing the maximum number of paths for
BGP4 load sharing
Load sharing enables the device to balance traffic to a route across multiple equal-cost paths of
the same route type (EBGP or IBGP).
To configure the device to perform BGP4 load sharing:
•
Enable IP load sharing if it is disabled.
•
Set the maximum number of BGP4 load sharing paths. The default maximum number is 1,
which means no BGP4 load sharing takes place by default. Refer to
NOTE
The maximum number of BGP4 load sharing paths cannot be greater than the maximum
number of IP load sharing paths.
How load sharing affects route selection
During evaluation of multiple paths to select the best path to a given destination (for installment in
the IP route table), the device performs a final comparison of the internal paths. The following
events occur when load sharing is enabled or disabled:
•
When load sharing is disabled, the device prefers the path with the lower device ID if the
compare-routerid command is enabled.
•
When load sharing and BGP4 load sharing are enabled, the device balances the traffic across
multiple paths instead of choosing just one path based on device ID.
Refer to
“How BGP4 selects a path for a route (BGP best path selection algorithm)”
on page 5 for a
description of the BGP4 algorithm.
When you enable IP load sharing, the device can load-balance BGP4 or OSPF routes across up to
four equal paths by default. You can change the number of load sharing paths to a value between 2
and 32.
Configuring route reflection parameters
Normally, all the BGP4 devices within an AS are fully meshed. Since each device has an IBGP
session with each of the other BGP4 devices in the AS, each device has a route for each IBGP
neighbor. For large ASs containing many IBGP devices, the IBGP route information in each
fully-meshed IBGP device may introduce too much administrative overhead.
To avoid this overhead, you can organize your IGP devices into clusters:
•
A cluster is a group of IGP devices organized into route reflectors and route reflector clients.
You configure the cluster by assigning a cluster ID on the route reflector and identifying the IGP
neighbors that are members of that cluster. All configuration for route reflection takes place on
the route reflectors. Clients are unaware that they are members of a route reflection cluster. All
members of the cluster must be in the same AS. The cluster ID can be any number from 1 –
4294967295, or an IP address. The default is the device ID.