Load Balancing In Ospf Version 2 And Ospfv3; Path Computation Element For Ospfv2; Management Information Base (Mib) For Ospfv3 - Cisco NCS 5500 Series Configuration Manuals

Load Balancing in OSPF Version 2 and OSPFv3

4. Routes learned from other OSPFv3 routers are installed in RIB.
Load Balancing in OSPF Version 2 and OSPFv3
When a router learns multiple routes to a specific network by using multiple routing processes (or routing
protocols), it installs the route with the lowest administrative distance in the routing table. Sometimes the
router must select a route from among many learned by using the same routing process with the same
administrative distance. In this case, the router chooses the path with the lowest cost (or metric) to the
destination. Each routing process calculates its cost differently; the costs may need to be manipulated to
achieve load balancing.
OSPF performs load balancing automatically. If OSPF finds that it can reach a destination through more than
one interface and each path has the same cost, it installs each path in the routing table. The only restriction
on the number of paths to the same destination is controlled by the maximum-paths (OSPF) command.
The range for maximum paths is from 1 to 8 and the default number of maximum paths is 8.

Path Computation Element for OSPFv2

A PCE is an entity (component, application, or network node) that is capable of computing a network path
or route based on a network graph and applying computational constraints.
PCE is accomplished when a PCE address and client is configured for MPLS-TE. PCE communicates its PCE
address and capabilities to OSPF then OSPF packages this information in the PCE Discovery type-length-value
(TLV) (Type 2) and reoriginates the RI LSA. OSPF also includes the Router Capabilities TLV (Type 1) in
all its RI LSAs. The PCE Discovery TLV contains the PCE address sub-TLV (Type 1) and the Path Scope
Sub-TLV (Type 2).
The PCE Address Sub-TLV specifies the IP address that must be used to reach the PCE. It should be a
loop-back address that is always reachable, this TLV is mandatory, and must be present within the PCE
Discovery TLV. The Path Scope Sub-TLV indicates the PCE path computation scopes, which refers to the
PCE ability to compute or participate in the computation of intra-area, inter-area, inter-AS or inter-layer TE
LSPs.
PCE extensions to OSPFv2 include support for the Router Information Link State Advertisement (RI LSA).
OSPFv2 is extended to receive all area scopes (LSA Types 9, 10, and 11). However, OSPFv2 originates only
area scope Type 10.
For detailed information for the Path Computation Element feature see the Implementing MPLS Traffic
Engineering module of the MPLS Configuration guide and the following IETF drafts:
• draft-ietf-ospf-cap-09
• draft-ietf-pce-disco-proto-ospf-00

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).
Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 6.3.x
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Implementing OSPF