You can configure multicast-only fast reroute (MoFRR)
to minimize packet loss in a network when there is a link failure.
When fast reroute is applied to unicast streams, an upstream
router preestablishes MPLS label-switched paths (LSPs) or precomputes
an IP loop-free alternate (LFA) fast reroute backup path to handle
failure of a segment in the downstream path.
In multicast routing, the traffic distribution graphs are usually
originated by the receiver. This is unlike unicast routing, which
usually establishes the path from the source to the receiver. Protocols
that are capable of establishing multicast distribution graphs are
PIM (for IP), multipoint LDP (for MPLS) and RSVP-TE (for MPLS). Of
these, PIM and multipoint LDP receivers initiate the distribution
graph setup, and therefore:
On the QFX series, MoFRR is supported in PIM domains.
On the MX Series and SRX Series, MoFRR is supported in
PIM and multipoint LDP domains.
The configuration steps are the same for enabling MoFRR for
PIM on all devices that support this feature, unless otherwise indicated.
Configuration steps that are not applicable to multipoint LDP MoFRR
are also indicated.
(For MX Series routers only) MoFRR is supported
on MX Series routers with MPC line cards. As a prerequisite,all the
line cards in the router must be MPCs.
To configure MoFRR on routers or switches:
- (For MX Series and SRX Series routers only) Set the router
to enhanced IP mode.
[edit chassis]
user@host# set network-services enhanced-ip
- Enable MoFRR.
[edit routing-options multicast]
user@host# set stream-protection
- (Optional) Configure a routing policy that filters for
a restricted set of multicast streams to be affected by your MoFRR
configuration.
You can apply filters that are based on source or group addresses.
For example:
[edit policy-options]
policy-statement mofrr-select {
term A {
from {
source-address-filter 225.1.1.1/32 exact;
}
then {
accept;
}
}
term B {
from {
source-address-filter 226.0.0.0/8 orlonger;
}
then {
accept;
}
}
term C {
from {
source-address-filter 227.1.1.0/24 orlonger;
source-address-filter 227.4.1.0/24 orlonger;
source-address-filter 227.16.1.0/24 orlonger;
}
then {
accept;
}
}
term D {
from {
source-address-filter 227.1.1.1/32 exact
}
then {
reject; #MoFRR disabled
}
}
...
}
- (Optional) If you configured a routing policy to filter
the set of multicast groups to be affected by your MoFRR configuration,
apply the policy for MoFRR stream protection.
[edit routing-options multicast stream-protection]
user@host# set policy policy-name
For example:
routing-options {
multicast {
stream-protection {
policy mofrr-select
}
}
}
- (Optional) In a PIM domain with MoFRR, allow MoFRR to
be applied to any-source multicast (ASM) (*,G) joins.
This is not supported for multipoint LDP MoFRR.
[edit routing-options multicast stream-protection]
user@host# set mofrr-asm-starg
- (Optional) In a PIM domain with MoFRR, allow only a disjoint
RPF (an RPF on a separate plane) to be selected as the backup RPF
path.
This is not supported for multipoint LDP MoFRR. In a multipoint
LDP MoFRR domain, the same label is shared between parallel links
to the same upstream neighbor. This is not the case in a PIM domain,
where each link forms a neighbor. The mofrr-disjoint-upstream-only statement does not allow a backup RPF path to be selected if the
path goes to the same upstream neighbor as that of the primary RPF
path. This ensures that MoFRR is triggered only on a topology that
has multiple RPF upstream neighbors.
[edit routing-options multicast stream-protection]
user@host# set mofrr-disjoint-upstream-only
- (Optional) In a PIM domain with MoFRR, prevent sending
join messages on the backup path, but retain all other MoFRR functionality.
This is not supported for multipoint LDP MoFRR.
[edit routing-options multicast stream-protection]
user@host# set mofrr-no-backup-join
- (Optional) In a PIM domain with MoFRR, allow new primary
path selection to be based on the unicast gateway selection for the
unicast route to the source and to change when there is a change in
the unicast selection, rather than having the backup path be promoted
as primary. This ensures that the primary RPF hop is always on the
best path.
When you include the mofrr-primary-selection-by-routing statement, the backup path is not guaranteed to get promoted to
be the new primary path when the primary path goes down.
This is not supported for multipoint LDP MoFRR.
[edit routing-options multicast stream-protection]
user@host# set mofrr-primary-path-selection-by-routing
