Management Information Base (Mib) For Ospfv3 - Cisco NCS 6000 Series Configuration Manual

Implementing OSPF

Management Information Base (MIB) for OSPFv3

Cisco IOS XR supports full MIBs and traps for OSPFv3, as defined in RFC 5643. The RFC 5643 defines
objects of the Management Information Base (MIB) for use with the Open Shortest Path First (OSPF) Routing
Protocol for IPv6 ( OSPF version 3).
The OSPFv3 MIB implementation is based on the IETF draft Management Information Base for OSPFv3 (
draft-ietf-ospf-ospfv3-mib-8). Users need to update the NMS application to pick up the new MIB when
upgraded to RFC 5643.
Multiple OSPFv3 Instances
SNMPv3 supports "contexts" that can be used to implement MIB views on multiple OSPFv3 instances, in the
same system.
OSPFv2 Unequal Cost Load Balancing
Unequal Cost Load Balancing feature in Cisco IOS XR OSPFv2 feature enables Unequal Cost Multipath
(UCMP) calculation based on configured prefix-list and based on variance factor. UCMP path can be calculated
for all prefixes or only for selected prefixes based on the configuration. Selected interfaces can be excluded
to be used as a candidate for UCMP paths. The calculated UCMP paths are then installed in the routing
information base (RIB) subject to the max-path limit.
The OSPFv2 interior gateway protocol is used to calculate paths to prefixes inside an autonomous system.
OSPF calculates up to maximum paths (max-path) equal cost multi-paths (ECMPs) for each prefix, where
max-path is either limited by the router support or is configured by the user.
UCMP Paths Calculation
In some topologies, alternate paths to prefix exist even though their metric is higher then the metric of the
best path(s). These paths are called Unequal Cost Multipaths (UCMPs). These paths are guaranteed to be loop
free. Users can send some portion of the traffic down these paths to better utilize the available bandwidth.
However, the UCMP paths are not discovered by the traditional Dijkstra calculation. Additional computation
is required to discover these paths.
Unequal Cost Multipath Load-balancing for OSPF
The unequal cost multipath (UCMP) load-balancing adds the capability with Open Shortest Path First (OSPF)
to load-balance traffic proportionally across multiple paths, with different cost. Without UCMP enabled, only
the best cost paths are discovered by OSPF (ECMP) and alternate higher cost paths are not computed.
Generally, higher bandwidth links have lower IGP metrics configured, so that they form the shortest IGP
paths. With the UCMP load-balancing enabled, IGP can use even lower bandwidth links or higher cost links
for traffic, and can install these paths to the forwarding information base (FIB). OSPF installs multiple paths
to the same destination in FIB, but each path will have a 'load metric/weight' associated with it. FIB uses this
load metric/weight to decide the amount of traffic that needs to be sent on a higher bandwidth path and the
amount of traffic that needs to be sent on a lower bandwidth path.
The UCMP computation is provided under OSPF VRF context, enabling UCMP computation for a particular
VRF. For default VRF the configuration is done under the OSPF global mode. The UCMP configuration is
also provided with a prefix-list option, which would limit the UCMP computation only for the prefixes present
in the prefix-list. If prefix-list option is not provided, UCMP computation is done for the reachable prefixes
Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 6.4.x
Management Information Base (MIB) for OSPFv3
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