User`s manual

OSPF Configuration Basics
The Switch supports either RIP or OSPF for unicast routing. Only one of these protocols may be enabled at a
time. If you want to enable a different protocol, you must first disable the protocol currently running.
RFC compliance
The Switch's OSPF implementation complies with:
OSPFv2 RFC1583
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RFC 1765 Link Database Overflow●
RFC 1850 OSPF MIB●
Important:
This section assumes you are familiar with OSPF. If not, refer to the RFCs listed above or one of the
many OSPF books available.
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You can configure an interface as an Internal Router (IR) or Area Border Router (ABR), but not an
Autonomous System Border Router (ASBR).
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When you connect this Switch to an existing OSPF network that already has selected a Designated
Router (DR) and a Backup Designated Router (BDR), the newly connected Switch accepts the existing
DR and BDR.
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OSPF may be enabled and disabled without rebooting the Switch.●
When you change the router ID with OSPF enabled, the OSPF interface is reset, its Link State Database
flushed and relearned without a reboot.
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On an OSPF routing interface that includes more than one port,
an OSPF link down event occurs only if every port on the interface is down.
❍
an OSPF link up event occurs when a link is established with any one port.❍
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All OSPF router interfaces must be assigned an OSPF area. By default, an interface is assigned to the
backbone, area 0.0.0.0.
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When an interface is assigned to an area, all subnets on that interface are automatically included.●
Simple password authentication is included.●
Terms
area_id - a number assigned to identify an OSPF area, represented in dotted IP format
autonomous system (AS) - a single IP domain.
backbone - Area 0.0.0.0 required by OSPF. All areas in an autonomous system must be connected to the
backbone.
normal area - an area that is not Area 0.0.0.0 and not a stub or not-so-stubby area. External routes can be
distributed into normal areas.
stub area - an area only connected to one area; route information is not advertised into stub areas
not-so-stubby area (NSSA) - the same as a stub area except that external routes learned by an Autonomous
System Border Router can be advertised within the NSSA. Likewise, external routes learned in an NSSA can be
advertised to other areas.
designated router (DR) and backup designated router (BDR) - the designated router is the OSPF router on
an IP subnet with the highest priority value. The Backup Designated Router is the one with the second highest
value. The only time the DR or BDR changes is if the existing one fails. In this event, OSPF selects a new DR or
BDR. See priority below.
priority - a number from 0 to 127 used to determine a new DR or BDR should the original one fail. The higher
the number, the higher the router's priority and its selection. A router that acts as a DR or a BDR has an
increased processing load. To prevent a router from being selected, assign a priority of 0.
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