# OSPF **URL:** https://forum.networklessons.com/c/routing-switching/ospf/11.md [Latest](https://forum.networklessons.com/latest.md) · [Categories](https://forum.networklessons.com/categories.md) --- ## [About the OSPF category](https://forum.networklessons.com/t/about-the-ospf-category/17)
**Author:** [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)\ **Replies:** 0\ **Last updated:** [December 13, 2016, 12:33pm UTC](https://forum.networklessons.com/t/about-the-ospf-category/17 "2016-12-13T12:33:21Z")
OSPF is a link-state routing protocol that uses LSAs (Link State Advertisements) and the LSDB (Link State Database) to exchange routing information and to build a topology. Any OSPF related questions can be discussed her… --- ## [Virtual-Links and NSSA Areas](https://forum.networklessons.com/t/virtual-links-and-nssa-areas/58825)
**Author:** [@jonas.huesler](https://forum.networklessons.com/u/jonas.huesler)\ **Replies:** 2\ **Last updated:** [July 21, 2026, 11:45am UTC](https://forum.networklessons.com/t/virtual-links-and-nssa-areas/58825 "2026-07-21T11:45:45Z")
Hey everyone, I’ve been playing around with the different area types and virtual links. R7 redistributes its loopback0 interface with the address 7.7.7.7/32 into OSPF. R5/R6 translate the type 7 LSA into type 5 and … --- ## [OSPF Multi-Area Adjacency](https://forum.networklessons.com/t/ospf-multi-area-adjacency/58764)
**Author:** [@davidilles](https://forum.networklessons.com/u/davidilles)\ **Replies:** 3\ **Last updated:** [June 22, 2026, 4:41am UTC](https://forum.networklessons.com/t/ospf-multi-area-adjacency/58764 "2026-06-22T04:41:37Z")
Hello, everyone. I found this topic by accident while studying for SPCOR. I am not talking about having an ABR with interfaces in multiple areas, I am talking about a literal multi-area adjacency (one interface being in… --- ## [OSPF Forwarding Address](https://forum.networklessons.com/t/ospf-forwarding-address/58762)
**Author:** [@davidilles](https://forum.networklessons.com/u/davidilles)\ **Replies:** 3\ **Last updated:** [December 31, 2025, 9:16am UTC](https://forum.networklessons.com/t/ospf-forwarding-address/58762 "2025-12-31T09:16:20Z")
Hello, everyone. I have a quick question regarding OSPF’s FA. This topic is pretty confusing at times. When it comes to type 7 LSAs, FA makes perfect sense. Type 5 LSAs are the ones that confuse me, especially the req… --- ## [Best path selected for IP packet](https://forum.networklessons.com/t/best-path-selected-for-ip-packet/57485)
**Author:** [@huangrongeasy](https://forum.networklessons.com/u/huangrongeasy)\ **Replies:** 1\ **Last updated:** [June 6, 2025, 4:39am UTC](https://forum.networklessons.com/t/best-path-selected-for-ip-packet/57485 "2025-06-06T04:39:55Z")
please help to draw the packet flow of the network diagram from the switch to both two routers. thanks --- ## [Redistribution in ospf](https://forum.networklessons.com/t/redistribution-in-ospf/14671)
**Author:** [@mksoni4ccie](https://forum.networklessons.com/u/mksoni4ccie)\ **Replies:** 7\ **Last updated:** [February 28, 2025, 2:16pm UTC](https://forum.networklessons.com/t/redistribution-in-ospf/14671 "2025-02-28T14:16:01Z")
Please help me on below two queries. In ospf , what is difference between under the router ospf redistribute connected and redistribute connected subnets ? In which scenario/use case E1 metric will be used. Is th… --- ## [Adjacency Required for Learning Routes?](https://forum.networklessons.com/t/adjacency-required-for-learning-routes/51515)
**Author:** [@bkcashman](https://forum.networklessons.com/u/bkcashman)\ **Replies:** 0\ **Last updated:** [August 22, 2024, 2:42am UTC](https://forum.networklessons.com/t/adjacency-required-for-learning-routes/51515 "2024-08-22T02:42:44Z")
Hi, Hoping you can help understand what is happening in the following case. I have 4 Juniper routers connected in a ring by GRE tunnels. So router A ↔ B ↔ C ↔ D ↔ A. I’m using OSPF with interface type point to point.… --- ## [Null0 interface](https://forum.networklessons.com/t/null0-interface/49707)
**Author:** [@mjugal1999](https://forum.networklessons.com/u/mjugal1999)\ **Replies:** 1\ **Last updated:** [July 6, 2024, 7:04am UTC](https://forum.networklessons.com/t/null0-interface/49707 "2024-07-06T07:04:53Z")
Hello team, How does creating Null0 interface prevent loops? Sincerely, Jugal Modi --- ## [OSPF Control Plane Looping and p-bit](https://forum.networklessons.com/t/ospf-control-plane-looping-and-p-bit/49612)
**Author:** [@mjugal1999](https://forum.networklessons.com/u/mjugal1999)\ **Replies:** 1\ **Last updated:** [July 3, 2024, 2:52pm UTC](https://forum.networklessons.com/t/ospf-control-plane-looping-and-p-bit/49612 "2024-07-03T14:52:47Z")
Hello team, I was going through OSPF lectures and had some doubts: Question 1: How does OSPF avoid control plane looping? I did find an answer, however, couldn’t understand it clearly. To be specific it is point numb… --- ## [Defining routes and OSPF](https://forum.networklessons.com/t/defining-routes-and-ospf/47754)
**Author:** [@colinpaice3](https://forum.networklessons.com/u/colinpaice3)\ **Replies:** 2\ **Last updated:** [May 14, 2024, 10:50am UTC](https://forum.networklessons.com/t/defining-routes-and-ospf/47754 "2024-05-14T10:50:12Z")
I am trying to use frr on Linux to implement OSPF with IPV4. Do I have to define a static route myself - or does OSPF define a route for me. My scenario is One router has an IP address of 10.5.0.3 On another router s… --- ## [NSSA purpose](https://forum.networklessons.com/t/nssa-purpose/45617)
**Author:** [@Donjosephweb](https://forum.networklessons.com/u/Donjosephweb)\ **Replies:** 5\ **Last updated:** [April 2, 2024, 7:46am UTC](https://forum.networklessons.com/t/nssa-purpose/45617 "2024-04-02T07:46:30Z")
Hello, In a NSSA, type 5 LSA is replaced by Type 7, that means the amount of LSA flood remain same. So what are we achieving in terms of minimising LSA flooding, which was the original reason for creating a stub area. A… --- ## [Requirement of LSA#4](https://forum.networklessons.com/t/requirement-of-lsa-4/15292)
**Author:** [@ashish7aditya](https://forum.networklessons.com/u/ashish7aditya)\ **Replies:** 1\ **Last updated:** [September 7, 2021, 8:45am UTC](https://forum.networklessons.com/t/requirement-of-lsa-4/15292 "2021-09-07T08:45:17Z")
Hi All, just wanted to understand the need of LSA#4 once again .. I have attached one simple topology and in this context, I am still not able to understand why LSA#4 would be vital here for R2 to reach OE2 routes comi… --- ## [OSPF over DMVPN with redundant Hubs](https://forum.networklessons.com/t/ospf-over-dmvpn-with-redundant-hubs/31413)
**Author:** [@jessie.gares](https://forum.networklessons.com/u/jessie.gares)\ **Replies:** 3\ **Last updated:** [October 18, 2022, 8:02am UTC](https://forum.networklessons.com/t/ospf-over-dmvpn-with-redundant-hubs/31413 "2022-10-18T08:02:16Z")
Is there a lesson posted for a single OSPF Area with several Spoke Sites that need to connect to two head-end DMVPN Hubs that are located in two separate locations connected via a Point-to-Point? Secondly, is it common t… --- ## [OSPF and DN bit when unable to use "capability vrf-lite"](https://forum.networklessons.com/t/ospf-and-dn-bit-when-unable-to-use-capability-vrf-lite/30607)
**Author:** [@drobertson9356](https://forum.networklessons.com/u/drobertson9356)\ **Replies:** 0\ **Last updated:** [September 15, 2022, 5:33am UTC](https://forum.networklessons.com/t/ospf-and-dn-bit-when-unable-to-use-capability-vrf-lite/30607 "2022-09-15T05:33:40Z")
I am working on a particular practice lab has given me a headache for the past couple days. The lab is pre-configured with an L3VPN where OSPF is used as the PE-CE protocol, and there are a number of issues already intro… --- ## [Route-Map ACL behavior](https://forum.networklessons.com/t/route-map-acl-behavior/30263)
**Author:** [@stephen](https://forum.networklessons.com/u/stephen)\ **Replies:** 2\ **Last updated:** [September 8, 2022, 3:45pm UTC](https://forum.networklessons.com/t/route-map-acl-behavior/30263 "2022-09-08T15:45:19Z")
I’ve been reviewing a customer network that uses OSPF as their IGP. I found an interesting typo that I ended up building a demo lab using a different IP scheme in the interest of protecting their AS. I’ve been trying t… --- ## [Segment routing](https://forum.networklessons.com/t/segment-routing/25643)
**Author:** [@equnguy](https://forum.networklessons.com/u/equnguy)\ **Replies:** 1\ **Last updated:** [April 5, 2022, 4:48am UTC](https://forum.networklessons.com/t/segment-routing/25643 "2022-04-05T04:48:35Z")
Dear all, In OSPF segment routing, prefix SID is defined under loopback0 interface that belong area 0 toward to core side. However, we want segment routing also work at access side which belong area x which not includ… --- ## [OSPF flap counter](https://forum.networklessons.com/t/ospf-flap-counter/15059)
**Author:** [@ashish7aditya](https://forum.networklessons.com/u/ashish7aditya)\ **Replies:** 1\ **Last updated:** [August 6, 2021, 5:14am UTC](https://forum.networklessons.com/t/ospf-flap-counter/15059 "2021-08-06T05:14:49Z")
Hi, Is there any cmd o/p that can display number of time OSPF or LDP neighborship flapped .. Currently I rely only on the sys-logs .. Best Reg. Ashish JAIN --- ## [OSFP originate default route if present locally](https://forum.networklessons.com/t/osfp-originate-default-route-if-present-locally/14858)
**Author:** [@scramatte](https://forum.networklessons.com/u/scramatte)\ **Replies:** 2\ **Last updated:** [July 13, 2021, 7:38am UTC](https://forum.networklessons.com/t/osfp-originate-default-route-if-present-locally/14858 "2021-07-13T07:38:24Z")
Hello, I’ve got a router with eBGP session. I learned default route through this BGP session. I want to redistribute default route into my OSPF network but only if the default route is installed locally and active. I… --- ## [OSPF Default Route- Not all Routers](https://forum.networklessons.com/t/ospf-default-route-not-all-routers/14014)
**Author:** [@wrose](https://forum.networklessons.com/u/wrose)\ **Replies:** 4\ **Last updated:** [April 10, 2021, 5:11pm UTC](https://forum.networklessons.com/t/ospf-default-route-not-all-routers/14014 "2021-04-10T17:11:17Z")
Hello, I have many L3 switches in my campus and all are using OSPF. I have 2 separate internet circuits in 2 different locations. About half the LAN uses 1 circuit for its internet (default route) circuit and the other … --- ## [Ospf demand circuit](https://forum.networklessons.com/t/ospf-demand-circuit/13195)
**Author:** [@vijayjaggala23](https://forum.networklessons.com/u/vijayjaggala23)\ **Replies:** 2\ **Last updated:** [January 18, 2021, 9:15pm UTC](https://forum.networklessons.com/t/ospf-demand-circuit/13195 "2021-01-18T21:15:23Z")
I see no topic on ospf demand circuit. Could you please guide me on it. --- ## [OSPF & IPsec](https://forum.networklessons.com/t/ospf-ipsec/13239)
**Author:** [@brucey54](https://forum.networklessons.com/u/brucey54)\ **Replies:** 1\ **Last updated:** [January 6, 2021, 6:48am UTC](https://forum.networklessons.com/t/ospf-ipsec/13239 "2021-01-06T06:48:10Z")
Hi everyone, I have followed the following tutorial DMVPN Phase 2 OSPF Routing https://networklessons.com/cisco/ccie-enterprise-infrastructuredmvpn-phase-2-ospf-routing I would like to implement IPsec over OSPF do we … --- ## [OSPF route configuration problem](https://forum.networklessons.com/t/ospf-route-configuration-problem/11933)
**Author:** [@kikidelac44](https://forum.networklessons.com/u/kikidelac44)\ **Replies:** 3\ **Last updated:** [January 5, 2021, 2:33pm UTC](https://forum.networklessons.com/t/ospf-route-configuration-problem/11933 "2021-01-05T14:33:29Z")
Hello everyone, I have an OSPF configuration task where I need to send traffic between routers on specified routes. In the picture of logical scheme below you can see that traffic from Loopback0 on R3 needs to flow over… --- ## [OSPF: Reference Bandwidth & Interface Bandwidth](https://forum.networklessons.com/t/ospf-reference-bandwidth-interface-bandwidth/9215)
**Author:** [@sanjaynetworklessons](https://forum.networklessons.com/u/sanjaynetworklessons)\ **Replies:** 0\ **Last updated:** [December 17, 2019, 10:37pm UTC](https://forum.networklessons.com/t/ospf-reference-bandwidth-interface-bandwidth/9215 "2019-12-17T22:37:37Z")
OSPF Unit 1: Chapter: Introduction to OSPF | Reference Bandwidth & Interface Bandwidth I went through your video & Notes, i tried much, But I am not understanding, What is Reference Bandwidth & Interface Ban… --- ## [Https://networklessons.com/cisco/ccna-routing-switching-icnd2-200-105/ospf-multi-area-configuration](https://forum.networklessons.com/t/https-networklessons-com-cisco-ccna-routing-switching-icnd2-200-105-ospf-multi-area-configuration/8911)
**Author:** [@jktdgk](https://forum.networklessons.com/u/jktdgk)\ **Replies:** 0\ **Last updated:** [November 18, 2019, 11:34pm UTC](https://forum.networklessons.com/t/https-networklessons-com-cisco-ccna-routing-switching-icnd2-200-105-ospf-multi-area-configuration/8911 "2019-11-18T23:34:01Z")
Just wondering if you have a lab that taught in the lessons? Currently, I’m doing OSPF Multi-Area Configuration for CCNA and I wish I can import the same lab and practice in my GNS3 or packet tracer. --- ## [Isis vs ospf](https://forum.networklessons.com/t/isis-vs-ospf/4007)
**Author:** [@informfaizanmahmood](https://forum.networklessons.com/u/informfaizanmahmood)\ **Replies:** 2\ **Last updated:** [October 3, 2019, 10:00pm UTC](https://forum.networklessons.com/t/isis-vs-ospf/4007 "2019-10-03T22:00:43Z")
Hi, i am studying the ISIS routing protocol. and i have read that ISIS is more suitable to use in ISP environment rather than OSPF. Please Explain why ISIS is more preferable than OSPF. Thanks --- ## [GNS3 OSPF Summarization Lab](https://forum.networklessons.com/t/gns3-ospf-summarization-lab/8251)
**Author:** [@mcpp66](https://forum.networklessons.com/u/mcpp66)\ **Replies:** 1\ **Last updated:** [September 18, 2019, 1:06am UTC](https://forum.networklessons.com/t/gns3-ospf-summarization-lab/8251 "2019-09-18T01:06:23Z")
I have a question about the following lab: I replicated Rene’s video solution but I noticed that network 192.168.45.0 was not making it into the routing table of the other routers (Cerberus, Chimaera, and Cyclops). I … --- ## [Multiple OSPF instance and type 5 LSA](https://forum.networklessons.com/t/multiple-ospf-instance-and-type-5-lsa/7948)
**Author:** [@gazwoz](https://forum.networklessons.com/u/gazwoz)\ **Replies:** 0\ **Last updated:** [August 16, 2019, 1:34pm UTC](https://forum.networklessons.com/t/multiple-ospf-instance-and-type-5-lsa/7948 "2019-08-16T13:34:39Z")
Hello! I’ve been learning about type-5 LSAs or Autonomous System External LSAs and wondered how having more than one instance of OSPF running on the same device would affect this? Would you have to redistribute from on… --- ## [OSPF Virtual Link](https://forum.networklessons.com/t/ospf-virtual-link/3373)
**Author:** [@mriganksc](https://forum.networklessons.com/u/mriganksc)\ **Replies:** 9\ **Last updated:** [April 12, 2018, 6:06pm UTC](https://forum.networklessons.com/t/ospf-virtual-link/3373 "2018-04-12T18:06:18Z")
Hi Rene, In the scenario specified I am unable to reach from R5 to PC1. Help me --- ## [OSPF Broadcast Design Considerations](https://forum.networklessons.com/t/ospf-broadcast-design-considerations/7715)
**Author:** [@alias\_617](https://forum.networklessons.com/u/alias_617)\ **Replies:** 2\ **Last updated:** [July 19, 2019, 6:09am UTC](https://forum.networklessons.com/t/ospf-broadcast-design-considerations/7715 "2019-07-19T06:09:33Z")
I’m designing an OSPF network for a client’s new VPLS cloud. I’ve done this before using a /24 for the interface uplink to the VPLS. I’m curious if anyone has experience with larger (or even this large) of a subnet for… --- ## [OSPF DR/BDR election](https://forum.networklessons.com/t/ospf-dr-bdr-election/7436)
**Author:** [@apoorv\_jain2293](https://forum.networklessons.com/u/apoorv_jain2293)\ **Replies:** 1\ **Last updated:** [July 16, 2019, 7:02am UTC](https://forum.networklessons.com/t/ospf-dr-bdr-election/7436 "2019-07-16T07:02:05Z")
Hello, In the topic OSPF ABR Type 3 LSA Filtering (https://networklessons.com/cisco/ccie-enterprise-infrastructureospf-abr-type-3-lsa-filtering-on-cisco-ios), the R4#show ip ospf neighbor snippet shows that R4 is electe… [Next page](https://forum.networklessons.com/c/routing-switching/ospf/11.md?page=1)