How To Implement Ospf - Cisco NCS 6000 Series Configuration Manual

How to Implement OSPF

in OSPF. The number of UCMP paths to be considered and installed is controlled using the variance
configuration. Variance value identifies the range for the UCMP path metric to be considered for installation
into routing information base (RIB/FIB) and is defined in terms of a percentage of the primary path metric.
Total number of paths, including ECMP and UCMP paths together is limited by the max-path configuration
or by the max-path capability of the platform.
There is an option to exclude an interface from being used for UCMP computation. If it is desired that a
particular interface should not be considered as a UCMP nexthop, for any prefix, then use the UCMP exclude
interface command to configure the interface to be excluded from UCMP computation.
Enabling the UCMP configuration indicates that OSPF should perform UCMP computation for the all the
reachable OSPF prefixes or all the prefixes permitted by the prefix-list, if the prefix-list option is used. The
UCMP computation happens only after the primary SPF and route calculation is completed. There would be
a configurable delay (default delay is 100 ms) from the time primary route calculation is completed and UCMP
computation is started. Use the UCMP delay-interval command to configure the delay between primary SPF
completion and start of UCMP computation. UCMP computation will be done during the fast re-route
computation (IPFRR does not need to be enabled for UCMP computation to be performed). If IPFRR is
enabled, the fast re-route backup paths will be calculated for both the primary equal cost multipath ( ECMP)
paths and the UCMP paths.
To manually adjust UCMP ratio, use any command that changes the metric of the link.
• By using the bandwidth command in interface configuration mode
• By adjusting the OSPF interface cost on the link
How to Implement OSPF
This section contains the following procedures:
Enabling OSPF
This task explains how to perform the minimum OSPF configuration on your router that is to enable an OSPF
process with a router ID, configure a backbone or nonbackbone area, and then assign one or more interfaces
on which OSPF runs.
Before you begin
Although you can configure OSPF before you configure an IP address, no OSPF routing occurs until at least
one IP address is configured.
SUMMARY STEPS
1. configure
2. Do one of the following:
3. router-id { router-id }
4. area
5. interface type interface-path-id
Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 6.4.x
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• router ospf process-name
• router ospfv3 process-name
area-id
Implementing OSPF