Route Redistribution For Ospf; Ospf Shortest Path First Throttling - Cisco ASR 9000 Series Configuration Manual

Implementing OSPF
• If both critical-priority and high-priority route policies are specified, and no maps are specified for
• If only medium-priority route policy is specified and no maps are specified for high priority or critical
prefix-set ospf-medium-prefixes
0.0.0.0/0 ge 32
end-set

Route Redistribution for OSPF

Redistribution allows different routing protocols to exchange routing information. This technique can be used
to allow connectivity to span multiple routing protocols. It is important to remember that the redistribute
command controls redistribution into an OSPF process and not from OSPF. See
Implementing OSPF , on page 414

OSPF Shortest Path First Throttling

OSPF SPF throttling makes it possible to configure SPF scheduling in millisecond intervals and to potentially
delay SPF calculations during network instability. SPF is scheduled to calculate the Shortest Path Tree (SPT)
when there is a change in topology. One SPF run may include multiple topology change events.
The interval at which the SPF calculations occur is chosen dynamically and based on the frequency of topology
changes in the network. The chosen interval is within the boundary of the user-specified value ranges. If
network topology is unstable, SPF throttling calculates SPF scheduling intervals to be longer until topology
becomes stable.
OL-30423-03
◦ Permitted prefixes matching high-priority route policy are assigned to a high-priority queue.
◦ Permitted prefixes matching medium-priority route policy are placed in a medium-priority queue.
◦ Unmatched prefixes, including /32s, are moved to a low-priority queue.
medium priority:
◦ Permitted prefixes matching critical-priority route policy are assigned to a critical-priority queue.
◦ Permitted prefixes matching high-priority route policy are assigned to a high-priority queue.
◦ Unmatched prefixes, including /32s, are placed in a low-priority queue.
priority:
◦ Permitted prefixes matching medium-priority route policy are assigned to a medium-priority queue.
◦ Unmatched prefixes, including /32s, are placed in a low-priority queue.
Use the [no] spf prefix-priority route-policy rpl command to prioritize OSPF prefix installation into
the global RIB during SPF.
SPF prefix prioritization is disabled by default. In disabled mode, /32 prefixes are installed into the
global RIB, before other prefixes. If SPF prioritization is enabled, routes are matched against the
route-policy criteria and are assigned to the appropriate priority queue based on the SPF priority set.
Unmatched prefixes, including /32s, are placed in the low-priority queue.
If all /32s are desired in the high-priority queue or medium-priority queue, configure this single route
map:
Cisco ASR 9000 Series Aggregation Services Router Routing Configuration Guide, Release 5.1.x
for an example of route redistribution for OSPF.
Route Redistribution for OSPF
Configuration Examples for
347