Analyser
"OSPF network analyser" (OSPFana) is part of OSPFviz since revision 2.6. This analyser looks in the topology discovered by OSPFviz and performs some basic checks. If some checks fail OSPFana writes the result and a suggestion in the analysis html section. It does not change anything in your network. It is up to you (or the network administrator) to read the html page and to decide if these suggestions really apply to your network and if you want to do something about it.
OSPFana comes with these checks:
- [check 01] ping: ping the router id of each OSPF router
Management software normally addresses the router by its router ID, so it should be pingable.
- [check 02] bandwidth match: check if the bandwidth settings on both sides of a link match
They can differ if you set the bandwidth manually e.g. for serial links or tunnel interfaces. Different bandwidth results in different metric and this causes asymmetrical routes.
- [check 03] cost-reference: see if the OSPF cost-reference value is identical on all OSPF routers
This value has to be identical, or asymmetrical routes will exist.
- [check 04] little areas: find very little areas containing only of a few links
Too little areas are wasted memory and CPU usage in the routers.
- [check 05] multiple links: find multiple links between two routers with identical metric
This is most likely not a redundant path, but a Vlan trunk link running on the same wire.
- [check 06] capacity rules: are the recommended capacity rules met? [available since version 0.6]
Cisco released guidelines for the design of an OSPF network. This guide recommends among other things to have maximum 50 router per area, 60 neighbors per router and max. three areas per router.
- [check 07] authentication: is OSPF authentication used? [available since version 0.6]
Without authentication every IP device may communicate with the OSPF routers and inject false routes. This may be a security problem unless you have secured your network with different mechanisms.
- [check 08] adjacent neighbors: Are there OSPF neighbors that are not in the FULL state? [available since version 0.6]
If two neighbors are not configured with same settings (e.g. same subnet mask, MTU, area ID) they will not reach FULL state and never exchange link state information. Only routers on a broadcast network that don't have the DR or BDR role may reside in the 2WAY state.
- [check 09] loopback: Is the router ID a physical interface or a loopback interface? [available since version 0.6]
Always have a loopback interface as source for the OSPF router id, because this interface never goes down (unless administratively disabled).
- [check 10] designated router: For how many links it each router the DR? [available since version 0.6]
OSPF routers elect a designated router (DR) for every broadcast network. The work of a DR is memory intensive so we check if each router is DR only for a few links/networks.
When using a diagnosis tool, please keep in mind that no software can substitute a firm knowledge of routing operations in general and the OSPF routing protocol in particular.
