缺省的方式是基于前缀的负载均衡，从多个等价路径中随机选择。
但可以配置基于包（per-packet)的负载均衡。
负载均衡和硬件系统密切相关：
internet processor 1 ：缺省最大8条进行负载均衡。配置了per-packet以后按照逐包负载均衡。
internet processor 2: 缺省最大16条进行负载均衡。配置了pre-packet后按照逐流（pre-flow)方式，相同的流走相同的下一跳。
JUNOS的pfe表里体现不出负载均衡来。
对于未启用逐包均衡的情况：
admin@jr4# run show route table inet.0
inet.0: 10 destinations, 10 routes (10 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both
10.0.0.1/32 *[OSPF/10] 02:01:43, metric 2
> to 10.24.0.2 via ge-1/3/0.201
to 10.34.0.3 via ge-1/3/0.202
10.0.0.2/32 *[OSPF/10] 02:01:43, metric 1
> to 10.24.0.2 via ge-1/3/0.201
10.0.0.3/32 *[OSPF/10] 02:02:21, metric 1
> to 10.34.0.3 via ge-1/3/0.202
10.0.0.4/32 *[Direct/0] 02:03:06
> via lo0.0
10.24.0.0/24 *[Direct/0] 02:03:07
> via ge-1/3/0.201
10.24.0.4/32 *[Local/0] 02:03:07
Local via ge-1/3/0.201
10.34.0.0/24 *[Direct/0] 02:03:06
> via ge-1/3/0.202
10.34.0.4/32 *[Local/0] 02:03:06
Local via ge-1/3/0.202
10.123.0.0/24 *[OSPF/10] 02:01:43, metric 2
to 10.24.0.2 via ge-1/3/0.201
> to 10.34.0.3 via ge-1/3/0.202
224.0.0.5/32 *[OSPF/10] 02:03:07, metric 1
MultiRecv
[edit]
admin@jr4# run show pfe route ip
IPv4 Route Table 0, default.0, 0x0:
Destination NH IP Addr Type NH ID Interface
------------ --------------- -------- ----- ---------
default Reject 36 RT-ifl 0
0.0.0.0 Discard 34 RT-ifl 0
10.0.0.1 10.24.0.2 Unicast 546 RT-ifl 0 ge-1/3/0.201 ifl 67
10.0.0.2 10.24.0.2 Unicast 546 RT-ifl 0 ge-1/3/0.201 ifl 67
10.0.0.3 10.34.0.3 Unicast 545 RT-ifl 0 ge-1/3/0.202 ifl 68
10.0.0.4 10.0.0.4 Local 544 RT-ifl 0
10.24.0/24 Resolve 537 RT-ifl 67 ge-1/3/0.201 ifl 67
10.24.0.0 10.24.0.0 Recv 535 RT-ifl 67 ge-1/3/0.201 ifl 67
10.24.0.2 10.24.0.2 Unicast 546 RT-ifl 67 ge-1/3/0.201 ifl 67
10.24.0.4 10.24.0.4 Local 536 RT-ifl 0
10.24.0.255 Bcast 534 RT-ifl 67 ge-1/3/0.201 ifl 67
10.34.0/24 Resolve 543 RT-ifl 68 ge-1/3/0.202 ifl 68
10.34.0.0 10.34.0.0 Recv 541 RT-ifl 68 ge-1/3/0.202 ifl 68
10.34.0.3 10.34.0.3 Unicast 545 RT-ifl 68 ge-1/3/0.202 ifl 68
10.34.0.4 10.34.0.4 Local 542 RT-ifl 0
10.34.0.255 Bcast 540 RT-ifl 68 ge-1/3/0.202 ifl 68
10.123.0/24 10.34.0.3 Unicast 545 RT-ifl 0 ge-1/3/0.202 ifl 68
224/4 mdiscard 35 RT-ifl 0
224.0.0.1 Mcast 31 RT-ifl 0
224.0.0.5 Mcast 31 RT-ifl 0
224.0.0.6 Mgroup 538 RT-ifl 0
255.255.255.255 Bcast 32 RT-ifl 0
对于启用了pre-packet均衡的情况：
admin@jr1# show
routing-options {
forwarding-table {
export lb;
}
}
protocols {
ospf {
area 0.0.0.0 {
interface lo0.0;
interface ge-1/3/0.100;
}
}
}
policy-options {
policy-statement lb {
then {
load-balance per-packet;
}
}
}
[edit]
admin@jr1# run show route table inet.0
inet.0: 9 destinations, 9 routes (9 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both
10.0.0.1/32 *[Direct/0] 2d 23:05:55
> via lo0.0
10.0.0.2/32 *[OSPF/10] 2d 23:02:02, metric 1
> to 10.123.0.2 via ge-1/3/0.100
10.0.0.3/32 *[OSPF/10] 2d 23:02:07, metric 1
> to 10.123.0.3 via ge-1/3/0.100
10.0.0.4/32 *[OSPF/10] 02:03:13, metric 2
> to 10.123.0.2 via ge-1/3/0.100
to 10.123.0.3 via ge-1/3/0.100
10.24.0.0/24 *[OSPF/10] 02:03:18, metric 2
> to 10.123.0.2 via ge-1/3/0.100
10.34.0.0/24 *[OSPF/10] 02:07:44, metric 2
> to 10.123.0.3 via ge-1/3/0.100
10.123.0.0/24 *[Direct/0] 2d 23:05:55
> via ge-1/3/0.100
10.123.0.1/32 *[Local/0] 2d 23:05:55
Local via ge-1/3/0.100
224.0.0.5/32 *[OSPF/10] 2d 23:05:56, metric 1
MultiRecv
[edit]
admin@jr1# run show pfe route ip
IPv4 Route Table 0, default.0, 0x0:
Destination NH IP Addr Type NH ID Interface
------------ --------------- -------- ----- ---------
default Reject 36 RT-ifl 0
0.0.0.0 Discard 34 RT-ifl 0
10.0.0.1 10.0.0.1 Local 540 RT-ifl 0
10.0.0.2 10.123.0.2 Unicast 542 RT-ifl 0 ge-1/3/0.100 ifl 67
10.0.0.3 10.123.0.3 Unicast 541 RT-ifl 0 ge-1/3/0.100 ifl 67
10.0.0.4 Unilist 262142 RT-ifl 0
10.24.0/24 10.123.0.2 Unicast 542 RT-ifl 0 ge-1/3/0.100 ifl 67
10.34.0/24 10.123.0.3 Unicast 541 RT-ifl 0 ge-1/3/0.100 ifl 67
10.123.0/24 Resolve 537 RT-ifl 67 ge-1/3/0.100 ifl 67
10.123.0.0 10.123.0.0 Recv 535 RT-ifl 67 ge-1/3/0.100 ifl 67
10.123.0.1 10.123.0.1 Local 536 RT-ifl 0
10.123.0.2 10.123.0.2 Unicast 542 RT-ifl 67 ge-1/3/0.100 ifl 67
10.123.0.3 10.123.0.3 Unicast 541 RT-ifl 67 ge-1/3/0.100 ifl 67
10.123.0.255 Bcast 534 RT-ifl 67 ge-1/3/0.100 ifl 67
224/4 mdiscard 35 RT-ifl 0
224.0.0.1 Mcast 31 RT-ifl 0
224.0.0.5 Mcast 31 RT-ifl 0
224.0.0.6 Mgroup 538 RT-ifl 0
255.255.255.255 Bcast 32 RT-ifl 0
[edit]
admin@jr1# run show pfe next-hop | match 262142
262142 Unilist ge-1/3/0.100 - IPv4 Ethernet 0 0x00000000 0x00000000
[edit]
admin@jr1#
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