Ospf And Ip; Passive Interfaces - Avaya 8800 Configuration Manual

5. R3 and R4 each form three adjacencies (one with each router on the NBMA
6. R1 and R2 each form two adjacencies (one with the DR and one with the BDR).

Passive interfaces

Use a passive interface to enable an interface to advertise into an OSPF domain while limiting
its adjacencies.
When you change the interface type to passive, the interface is advertised into the OSPF
domain as an internal stub network with the following behaviors:
• does not send Hello packets to the OSPF domain
• does not receive Hello packets from the OSPF domain
• does not form adjacencies in the OSPF domain
If an interface is configured as passive, it is advertised as an OSPF internal route. If the
interface is not a passive interface, to advertise a network into OSPF and not form OSPF
adjacencies, the interface must be configured as nonOSPF, and the local network must be
redistributed as an autonomous system external (ASE) LSA.

OSPF and IP

OSPF runs over IP, which means that an OSPF packet is sent with an IP data packet header.
The protocol field in the IP header is 89, which identifies it as an OSPF packet and distinguishes
it from other packets that use an IP header.
A destination in an OSPF route advertisement is expressed as an IP address and a variable-
length mask. Together, the address and the mask indicate the range of destinations to which
the advertisement applies.
Because the OSPF can specify a range of networks, it can send one summary advertisement
that represents multiple destinations. For example, a summary advertisement for the
destination 128.185.0.0 with a mask of 255.255.0.0 describes a single route to destinations
128.185.0.0 to 128.185.255.255.
Configuration — OSPF and RIP
subnet).
Open Shortest Path First
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