Configuration Guide User guide

FastIron Configuration Guide 1351
53-1002494-02
BGP4 memory considerations
BGP4 parameter changes after resetting neighbor sessions
The following parameter changes take effect only after the router BGP4 sessions are cleared, or
reset using the “soft” clear option. (Refer to “Closing or resetting a neighbor session” on
page 1457.)
The parameter are as follows:
• Change the Hold Time or Keep Alive Time.
• Aggregate routes.
• Add, change, or negate filter tables.
BGP4 parameter changes after disabling and re-enabling redistribution
The following parameter change takes effect only after you disable and then re-enable
redistribution:
• Change the default MED (metric).
BGP4 memory considerations
BGP4 handles a very large number of routes and therefore requires a lot of memory. For example,
in a typical configuration with just a single BGP4 neighbor, a BGP4 router may need to be able to
hold up to 80,000 routes. Many configurations, especially those involving more than one neighbor,
can require the router to hold even more routes. Brocade Layer 3 switches provide dynamic
memory allocation for BGP4 data. These devices automatically allocate memory when needed to
support BGP4 neighbors, routes, and route attribute entries. Dynamic memory allocation is
performed automatically by the software and does not require a reload.
Table 239 lists the maximum total amount of system memory (DRAM) BGP4 can use. The
maximum depends on the total amount of system memory on the device.
The memory amounts listed in the table are for all BGP4 data, including routes received from
neighbors, BGP route advertisements (routes sent to neighbors), and BGP route attribute entries.
The routes sent to and received from neighbors use the most BGP4 memory. Generally, the actual
limit to the number of neighbors, routes, or route attribute entries the device can accommodate
depends on how many routes the Layer 3 switch sends to and receives from the neighbors.
In some cases, where most of the neighbors do not send or receive a full BGP route table (about
80,000 routes), the memory can support a larger number of BGP4 neighbors. However, if most of
the BGP4 neighbors send or receive full BGP route tables, the number of BGP neighbors the
memory can support is less than in configurations where the neighbors send smaller route tables.
TABLE 239 Maximum memory usage
Platform Maximum memory BGP4 can use
FESX with 128 MB 30 MB
FSX with Management 1 module with 256 MB 130 MB
FSX with Management 2 module with 512 MB 400 MB