8.4.2 Load Balancing Specifications

The following table describes the specifications for multipath routing on the Switch.

Table 8-5: Multipath specifications
Item	Specifications	Remarks
Number of multipaths for a single destination network	2~16	-
Maximum number of multipaths that can be specified in the configuration	1 to 16 (Multipath is not generated when 1 is specified)	The maximum number of multipaths is specified for each routing protocol.
Maximum number of multipath routes	The value differs depending on the maximum number of multipaths handled by the switch. For details, see Table 8-6: Maximum number of multipath routes.	-
Routing protocols capable of generating multipaths	Static (IPv4) OSPF BGP4	-
Number of multipaths in a default configuration	Static (IPv4): 6 OSPF: 4 BGP4: 1 (multipaths are not generated)	-
Connection configuration	Can be used with any combination of line type and interface type. Concurrent use of different types of lines or interfaces is possible.	Multipaths between VRFs are not supported.

Legend:-: Not applicable

Table 8-6: Maximum number of multipath routes
Maximum number of multipaths set in the configuration*1	Handle by the device Maximum number of multipaths*2	Maximum number of multipath routes that can be handled23*4
1~4	4	1024 (512^#6)
5~8	8	512 (256^#6)
9 to 16, or multipath unused*5	16	256 (128^#6)

#1

The maximum number of multipaths specified for static routing (IPv4/IPv6), OSPF/OSPFv3, or BGP4/BGP4+, whichever is largest. For example, if the device configuration specifies a maximum number of multipaths of 6 for static routing and 3 for OSPF, the larger value of 6 applies.

Each routing protocol can generate a number of multipaths no greater than the maximum number defined for that protocol in the switch configuration. If a change is made to the maximum number of multipaths that affects how many multipaths the switch can handle, the changes will not take effect until the switch is restarted.

#2

The maximum value is determined at startup. If you change the maximum number of multipaths for a unicast protocol after the switch starts, it remains unchanged from the value determined at startup. To change the maximum multipath count, restart the switch after making the appropriate changes in the device configuration.

#3

The maximum number of multipath routes applies to the combined total of IPv4 and IPv6 routes. Note that multipath routes matching the next-hop IP addressand VRF are counted as the same multipath route.

#4

The maximum number of routes depends on the capacity limit for the number of table entries, but the capacity limit for multipath routes is the value here.

#5

When not using static routing (IPv4/IPv6), OSPF/OSPFv3, or BGP4/BGP4+, the switch does not handle multipath routes. In this case, the maximum values in the table apply.

#6

When VXLAN function is used, the max. value is the value in parentheses (half the normal value). [SL-L3A]

Using static routing as an example, the following table shows how the maximum multipath values change as you change the device configuration or restart the device.

Table 8-7: Maximum number of multipaths (static routing)
Seq.	Status	Maximum number of multipaths for static routing	Maximum number of multipaths handled by the switch
1	The switch starts without static routing configured.	-	16
2	You add a static route.	6^#1	16
3	The switch restarts.	6	8
4	Set the maximum number of multipaths for static routing to 3	3	8
5	The switch restarts.	3	4
6	You set the maximum multipath count for static routing to 5.	4^#2	4
7	The switch restarts.	5^#2	8

Legend:-: Not applicable

#1: If you configure static routes without specifying a maximum multipath value, the default value applies to the number of static multipaths. For details, see 8.4.3 Notes on using load balancing.
#2: You cannot generate statically routed multipaths that exceed the maximum number of multipaths the switch can handle. However, after you restart the switch, the maximum number of multipaths handled by the switch changes, and the value specified for static routing multipaths takes effect.

The following table describes the load balancing specifications implemented by the Switch.

Table 8-8: Load balancing specifications
Item	Specifications	Remarks
Path selection in multipaths	A value (hash value) is calculated and allocated to the designated output path. This hash value is derived from the following four fields: Source IP address Destination IP address Source TCP/UDP port number Destination TCP/UDP port number The transmission order is guaranteed within each session.	-
Multipath information in routing table	Hash values are assigned on a substantially equal basis to the output interfaces in the routing table.	[8.4.3 See 1 and 2 in "Notes on Using Load Balancing"
Weighting of paths	Not available	[8.4.3 See 1 in "Precautions When Using Load Balancing"
Processing of packets exceeding output bandwidth	Not reallocated to another path. The packets are retained within the switch as long as bandwidth continues to be exceeded. However, any overflow will be discarded.	-

Legend:-: Not applicable