OSPF: Difference between revisions
→Introduction
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auto-cost reference-bandwidth 1000
* What is a Demand Circuit?▼
Source: [https://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/5132-dc.html cisco.com]▼
OSPF sends hellos every 10 seconds and refreshes its link-state advertisements (LSAs) every 30 minutes. ▼
These functions maintain neighbor relationships and ensure that the link-state databases are accurate and use far less bandwidth than similar functions in Routing Information Protocol (RIP) and Interior Gateway Routing Protocol (IGRP). ▼
However, even this amount of traffic is undesirable on demand circuits. Using OSPF demand circuit options suppresses hello and LSA refresh functions. ▼
OSPF can establish a demand link to form an adjacency and perform initial database synchronization, the adjacency remains active even after Layer 2 of the demand circuit goes down.▼
Cisco IOS version 12.1(2)T introduces the flooding reduction feature for OSPF. ▼
This feature is intended to minimize traffic created by a periodic refresh of LSAs in OSPF domains with large number of LSAs. ▼
Unlike the OSPF demand circuit feature, flooding reduction is usually configured on leased lines. ▼
Flooding reduction uses same technique as demand circuits to suppress the periodic LSA refresh. ▼
This feature is submitted for standardization into the IETF OSPF working group.▼
The main difference between flooding reduction and demand circuits is that former suppresses only periodic LSA refreshes; it does not suppress periodic hello packets.▼
Thus, the flooding reduction feature does not impair the detection of a neighbor router going down.▼
ip ospf demand-circuit▼
* All Areas must connect to Area 0.
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* All Areas must connect to Area 0.
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▲ Source: [https://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/5132-dc.html cisco.com]
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▲ ip ospf demand-circuit
=Area Summary=
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