Editing Open Shortest Path First (section)

==Applications==
OSPF is a widely deployed routing protocol that can converge a network in a few seconds and guarantee loop-free paths. It has many features that allow the imposition of policies about the propagation of routes that it may be appropriate to keep local, for load sharing, and for selective route importing. IS-IS, in contrast, can be tuned for lower overhead in a stable network, the sort more common in ISP than enterprise networks. There are some historical accidents that made IS-IS the preferred IGP for ISPs, but ISPs today may well choose to use the features of the now-efficient implementations of OSPF,<ref>{{Cite conference
  | first = Howard
  | last = Berkowitz
  | title = OSPF Goodies for ISPs
  | url = https://www.nanog.org/meetings/abstract?id=1149
  | archive-url = https://web.archive.org/web/20160612140344/https://www.nanog.org/meetings/abstract?id=1149
  | archive-date = 2016-06-12
  | conference = North American Network Operators Group NANOG 17
  | year = 1999
  | place = Montreal
}}</ref> after first considering the pros and cons of IS-IS in service provider environments.<ref>{{Cite conference
  | first = Dave
  | last = Katz
  | title = OSPF and IS-IS: A Comparative Anatomy
  | url = https://www.nanog.org/meetings/abstract?id=1084
  | archive-url = https://web.archive.org/web/20180620232619/https://www.nanog.org/meetings/abstract?id=1084
  | archive-date = 2018-06-20
  | conference = North American Network Operators Group NANOG 19
  | year = 2000
  | place = Albuquerque
}}</ref>

{{Citation needed span|text=OSPF can provide better load-sharing on external links than other IGPs.|date=September 2023}} When the default route to an ISP is injected into OSPF from multiple ASBRs as a Type I external route and the same external cost specified, other routers will go to the ASBR with the least path cost from its location. This can be tuned further by adjusting the external cost. If the default route from different ISPs is injected with different external costs, as a Type II external route, the lower-cost default becomes the primary exit and the higher-cost becomes the backup only.