You want to configure per-fpacket load balancing for all routes on Router-1.
Which configuration example accomplishes this?
A.
routing-options {
forwarding-table {
export ECMP;
}
}
policy-options {
policy-statement ECMP {
term first {
then {
load-balance per-packet;
}
}
}
}
B.
routing-options {
export ECMP;
}
policy-options {
policy-statement ECMP {
term first {
then {
load-balance per-packet;
}
}
}
}
C.
routing-options {
forwarding-table {
export ECMP;
}
}
policy-options {
policy-statement ECMP {
term first {
from protocol ospf;
then {
load-balance per-packet;
}
}
}
}
D.
routing-options {
forwarding-table {
export ECMP;
}
}
policy-options {
policy-statement ECMP {
term first {
from protocol ospf;
then {
load-balance ECMP;
}
}
}
}
Explanation:
Equal-Cost Multipath (ECMP)Equal-Cost Multipath (ECMP) is a layer 3 mechanism for achieving load balancing for a path with multiple equal cost next-hops. By default, in the event of equal-cost next-hops Juniper will randomly pick one next-hop per route to install for hardware forwarding. There is also an option that allows multiple next-hops to be installed into hardware, known as “per-packet load balancing”.
The term “per-packet load balancing” as used by Juniper is actually misleading in two ways. First, only the first generation Internet Processor I ASIC based routers were capable of true per-packet load-balancing, which is generally not a desirable behavior. All other Juniper routers actually implement a “per-flow” load-balancing, which prevents packet reordering, but the configuration element is still called “per-packet” for compatibility. Second, this option doesn’t actually have a direct relationship to “how” the packets are forwarded at all, it simply enables the installation of multiple next-hops for the same route.
An example configuration, which enabled per-packet load balancing for every prefix at the time it is exported to the forwarding table, is provided below:
policy-options {
policy-statement your-name-here {
then {
load-balance per-packet;
}
}
}
routing-options {
forwarding-table {
export [ your-name-here ];
}
}