Questions tagged [ospf]

For questions about OSPF. Open Shortest Path First (OSPF) is a link-state routing protocol for Internet Protocol (IP) networks.

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24 views

Why is OSPF more popular than IS-IS in enterprise networks? [closed]

I've read that IS-IS is more popular than OSPF in Internet Service Providers due to historical reasons (mainly that initially IS-IS had better hardware support and wasn't for IP only). But why did ...
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2answers
362 views

IGP between 2 routers with an uncooperative router in the middle

I've got two routers, A and B. A gets some routes over BGP over a VPN connection, and has a leg on 10.0.0.0/24. It also can access the whole 10.0.0.0/16 via its default gateway. B is on 192.168.0.0/...
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59 views

What is exact meaning of broadcast network in OSPF?

According to rfc2328(OSPFv2), broadcast network is "Networks supporting many (more than two) attached routers, together with the capability to address a single physical message to all of the ...
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1answer
108 views

OSPF Fast-Reroute Question

I'm running into a wall when doing some research on OSPF FRR. I came across this excerpt from the Cisco documentation: "Not all routes can have repair paths. Multipath primary routes might have ...
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2answers
68 views

Understanding the OSPFv2 MD5 authentication when packets contain LLS data block

When an OSPFv2 packet does not contain the LLS data block, then the calculated MD5 hash should be on the "Auth Crypt Data" field. For example, here is a LS Update message which does not ...
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1answer
197 views

Is this a valid OSPF topology?

In the following topology: every Backbone router is an ABR. Router 2 belongs to three different areas, area 0, area 1, and area 4. is this a valid topology for OSPF ? it works as expected and it ...
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2answers
76 views

Routing Protocols and sharing information

I am running multiple Protocols on different Routers as so: R1-RIPv2 EIGRP OSPF R2-OSPF and RIPv2 R3-RIPv2 and EIGRP R4-EIGRP and OSPF This is not a practical exercise, it is just to explore how ...
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1answer
36 views

Junos not automatically advertising an address configured on loopback interface to OSPF

According to JNCIP study guide(page 156) from 2003, the Junos should advertise a prefix on lo0.0 interface to OSPF if the RID is not manually configured: JUNOS software automatically advertises a ...
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15 views

OSPF Router ID election query [duplicate]

I have a query regarding ospf router id election. Suppose I have a router with 3 connected interfaces. 10.1.1.0/24 11.1.1.0/24 12.1.1.0/24 I have enabled ospf area 0 on network 10.1.1.0 and 11.1.1....
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1answer
36 views

Brocade OSPFv3 Routes are not installed

I am trying to deploy OSPFv3 across our network. However a few routers do not install the OSPFv3 route's to their routing tables. For example, this router is able to ping a certain host on the network....
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1answer
374 views

How an OSPF network react when an attacker deactivate one of the network interfaces on the router?

I am a bit stuck with OSPF. Want to know how an OSPF network react when an attacker deactivate one of the network interfaces on the router? What are possible impacts on the network if this ...
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1answer
96 views

OSPF route advertising same subnet in same area 0?

Now: SW02 currently running OSPF area 0 with redistribute connected subnets which includes VLAN10 with another router/switches which isn't in the picture and not in the scope of this question; VLAN10 ...
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0answers
35 views

How should OSPF work over WiFi? [closed]

I've had problems running OSPF over my WiFi network, and it seems to be related to multicast. The routers can't maintain a neighbor relationship, and when I watch the packet traffic I see one router ...
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33 views

Distance Command in OSPFv3

Does anyone know if there is a way to specify the distance of a specific neighbor in OSPFv3 in a Cisco router/switch? You seem to be able to do it for an entire area, but not for a specific neighbor ...
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1answer
45 views

Layer 2 redundant network and OSPF

What is a recommended way (in terms of maintenance, simplicity and failsafe-ness) to essentially run a "ring" of switches, but allowing OSPF to run properly (so equal-cost-path routing can work - in ...
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41 views

Are OSPF standard areas consisting of only one router any use?

I am currently reviewing the OSPF configuration of an existing network in an attempt to streamline it. From a Layer 3 standpoint, this network consists of two core routers in Area 0 (CORE1 and CORE2) ...
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4answers
67k views

Why must all areas connect to an Area 0 backbone in OSPF?

This question is a literal repost of the same question asked on The Cisco Support Community. Answers are unique to Stack Exchange. Why is area 0 the backbone area in OSPF? Why must all other areas ...
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65 views

Connecting layer 3 switches together without trunking

I currently have 2x Juniper EX4200 and I'm looking into changing it into Ubiquiti EdgeSwitchs. The diagram: SW01 and SW02 are connected to each other using OSPF P2P. Both of the switches have their ...
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1answer
42 views

why does the show ip protocols command at each router for ospf router output not showing any Routing Information Source for all loopback 0?

NarS-R1(config)#router ospf 1 NarS-R1(config-router)#network 192.168.12.0 0.0.0.255 area 0 NarS-R1(config-router)#network 192.168.17.0 0.0.0.255 area 0 NarS-R1(config-router)#network 1.1.1.1 0.0.0.0 ...
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2answers
3k views

What is the election process of Router ID in OSPF?

I am a little confused on the process OSPF uses to select the Router ID. Is following correct for the selection of the router ID in OSPF? Manual configuration Highest IP address on a loopback ...
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0answers
17 views

Would two ospf neighbors ever move from full to exchange?

I understand that when moving upwards from init through exchange to full states, ospf neighbors use received DBD packets to know which LSAs they need and make LSReqs as necessary. But, would 2 ospf ...
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1answer
32 views

“ospfNbrIpAddr” parameter in RFC 4750 page 53

in RFC 4750 page 53, there is a parameter called "ospfNbrIpAddr", I am not sure exactly what it means. Suppose I have two router, they are connected through physical ethernet port1, router A port1: ...
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1answer
29 views

Do DR-Other router forwards Type 2 LSA received by DR?

In the Diagram below when R1 is newly added to Network Topology R1 and R2 become neighbors and exchange Type 1 LSA from R2, R3, R4. But how R1 knows Network LSA created by the DR in LAN(subnet 1). ...
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1answer
76 views

OSPF neighbor not working

I'm currently designing a spine leaf network, 2 Spine switches and 4 leaf switches. btw this in packet tracer. So in order its Spine1# and Spine2#, then Leaf1#, Leaf2#, Leaf3#, Leaf4#, and addresses ...
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1answer
229 views

Layer 2/3 Ring with VRRP/OSPF

I have a few questions about my understanding if this is possible and how to achieve the following. As per the example diagram (simplified from potential network) I have a ring network as shown below. ...
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1answer
143 views

Transient looping problems in Link State Routing versus Persistent looping problem in Distance Vector routing

Can someone please explain how looping problem is transient in case of link state routing, but is persistent in distance vector routing.(maybe with a nice example) Thanks in advance! :)
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2answers
10k views

How do I delete all OSPF settings on a router?

I'm using PacketTracer. I want to delete all OSPF settings on a router. I used clear ip ospf process but after that when I do show ip ospf I can still see the process, its area and all interfaces of ...
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1answer
45 views

How to make routing on edges of a router in center of OSPF routing?

Lets says I have 3 routers: R1, R2, R3... All three communicate with OSPF (with authentication and all) ... R1 <--> R2 <--> R3 Now I have R4 on one side of R1 ... R4 <--> R1 <--> R2 <...
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1answer
136 views

Segregated OSPF Networks, cross same physical path, how to segregate back out at other end?

I'm sorry for being basic in writing this question. I think the details have been covered though. What's happening here is, two separate networks are being brought into an isolated area over a ...
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1answer
135 views

How important is it for time to be synchronized between adjacent OSPF neighbors?

I have two routers that; when first powered up, will initially form full OSPF neighborship with each other and exchange their respective advertised routes with each other. After approximately 2 hours ...
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27 views

Ospf and routes distribution

I'm doing some little cenarios in gns3 for classes but its getting messy. Let's say i have a router, if only FastEthernet 0/0 is on, the sh ipv6 route shows all routes, including the OSPF inter area ...
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1answer
66 views

How can I get OSPF to see the VLANS that are trunked through the gigabit port

I am relatively new to this and I have been trying various configs but nothing is catching. I have three routers, with various vlans. The vlans are working. The routers are seeing each other using ...
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1answer
54 views

PacketTracer: Why can I not ping from one to another router?

I'm trying to ping from Router DC_GE to BE: I uploaded the Packet Tracer File (v. 7.2.1): https://www.4shared.com/file/aEsd_0Piiq/Topologie_Ausgangspunkt_MH.html CD_GE: CD_GE#show running-config ...
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1answer
35 views

Multiaccess link shows two Designated Routers in Area 0

I have four Cumulus routers set up with a single ethernet connection from r3 -> r1 -> r2 - r4. From r1, show ip ospf neighbor displays the following: **Neighbor ID Pri State Dead Time ...
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1answer
42 views

What is the need of LSA refresh after every 30 minutes?

What is the exact need of LSA being refreshed every 30 minutes.
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1answer
385 views
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1answer
108 views

Why backbone area can not be stub area in OSPF

If there is no ASBR used anywhere in topology. Is it safe to make a backbone area as a stub.
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1answer
52 views

Filter tagged route to downstream routers

I'd like to filter a redistributed route from EIGRP into OSPF to all routers in AREA2 and AREA34. I have tagged the route 10.90.100.0/24 with tag 90 at the Tampa router where its redistributed into ...
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2answers
44 views

OSPFv2 through firewall

My network. https://imgur.com/a/5QI1NNq So my question is, on the 3 yellow above. Sub networks, I've used static routing, but on the other side of the internet (blue field) I've used Ospfv2. on the ...
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1answer
36 views

OSPF: What's the consequence of two nssa area translator router

If NSSA area has 2 ABR, then usually one of them will be elected to be translator by router id. But what if I have 2 translator routers and both translate the message simultaneously? How to route in ...
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3answers
1k views

OSPF LSA type 3

This is what I know about LSA types from what I've learnt. LSA type 1 is circulated inside an area and doesn't get to other areas. LSA type 3 is sent from one area(From backbone to non-backbone and ...
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2answers
159 views

How to ping from PC on EIGRP area to PC on OSPF area without middle router?

This is my topology. And I can send a package to every router and PC within the colored area, how can I ping from a PC on EIGRP area to a PC on the OSPF area? I heard about default route but I saw it ...
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3answers
8k views

Split OSPF Area 0 Behavior - What happens?

To make my question as simple as possible, I put together a quick scenario: Area 0 spans two data centers with multiple routers/networks in each. Area 0 has two ABR's connected to area 1 that connect ...
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1answer
95 views

I need help in creating OSPF between MultiLayerSwitch and Routers in packet tracer

I know we cannot create OSPF with different subnets. What network addresses should I put in the MLS and R1 to make it adjacent? Here's the configuration for MLS: interface FastEthernet0/15 no ...
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3answers
11k views

What is the difference between broadcasting and flooding?

In Open shortest path first routing algorithm, the information about connected links is "flooded" throughout the network. How is flooding different from broadcasting?
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1answer
4k views

Why do we need master/slave relationship to exchange DBD in OSPF?

I am confused with master and slave relationship in OSPF? Why ospf need the election for master and slave relationship to exchange DBD?
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1answer
3k views

OSPF between Cisco & PFsense

Cisco OSPF has area 0 with 10.0.0.0/24. PFsense OSPF has area 0 with 10.0.0.0/24 and area 10 with 10.10.2.0/24 and area 20 with 192.168.122.0/24. The routers have full "FULL/DR" & "FULL/BDR" ...
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1answer
173 views

Is OSPF router ID unique per area?

I found online that the router ID must be unique within the OSPF domain. But what exactly is an OSPF domain (an area?). Let's take the following topology: Can R1 and R5 have the same router ID, as ...
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1answer
156 views

Colocation rack setup (OSPF, VRRP)

I'm not a networking guy, so sorry if I mix some words up. We're moving in a new datacenter and want to setup the networking the right way. We have 2 uplinks coming into our rack and they assigned two ...
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2answers
2k views

How do I determine how many routers are in an OSPF area?

Is there any show command which allows me to determine the number of routers in a specific OSPF area? I can use the show ip ospf database router command and consider each LSA represent one router, but ...

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