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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56 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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56 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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74 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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33 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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13 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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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
369 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
80 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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33 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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32 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
32 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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40 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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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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39 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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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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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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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
72 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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207 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
129 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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117 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
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
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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43 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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148 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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104 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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89 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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104 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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1answer
163 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
1k views

Multi Area OSPF configuration in cisco packet tracer

I am a bit confuse in the concept of multi area ospf. I posted 2 days ago. And I was asked to leave the one interfaces of each router out of the circle. Now the center circle is area 0. The top circle ...
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44 views

Giving different OSPF areas to a router

In the topology shown above each circle represent an area. Now I want to configure multi area OSPF on each router. So for the first router can I do like this: router ospf 109 network 192.168.11.0 0.0....
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47 views

What does multi area OSPF mean?

Does this mean that all the routers in a given topology should have different values of area or just one i.e. area 0?
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213 views

Routes stopped redistributing through OSPF [closed]

I was entering a number of secondary addresses on some VLANs. In total there were 10 secondary addresses added. The subnets added were from three publically routable /24s (I will call them 25.0/24, ...
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1k views

OSPF increase bandwidth with load-balancing

This is my current setup where i have 40Gbps links between all 4 switches running OSPF using L3 links between them but now i want to double my bandwidth between switches so i am planning to add (...
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98 views

explanation on redistribution

I'm having trouble understanding redistribution in reference to this topology R1, R2, R3 and R4 have OSPF enabled on all IP interfaces, all in Area 0 R5 has a default route pointing to the VRRP ...
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1answer
149 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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1answer
371 views

What happens in Exstart state in OSPF neighbor state? Will DBDs be exchanged in that state?

According to my knowledge, DBD exchange happens in Exchange state.
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128 views

Why can the BGP protocol be implemented across routers, but the OSPF protocol can only be implemented direct connected routers?

Why can the BGP protocol be implemented across routers? But the OSPF protocol can only be implemented on directly connected routers? Is the OSPF protocol based on IP? we know the BGP is based on ...
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160 views

Do the Master/Slave Election happen in Broadcast Domain in OSPF? if not Why?

According to my knowledge, Mater-Slave election is needed to decide who will to start communication between two routers. In broadcast domains all the DR other routers communicate with DR. Is there a ...
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1answer
74 views

Understanding OSPF

In OSPF, what happens first, the SPF tree or the SPF algorithm? Once the LSDB is created does the SPF tree get created first and then the SPF algorithm runs or does the SPF algorithm run and the SPF ...
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64 views

OSPF and /30 for IPSEC VPN links on routes which support routing (as opposed to polices)

Traditionally i have always set IPSEC policies as /24 (/16 etc) on routers that had policies for encrypting IPSEC traffic (as opposed to routes). I have since started using a router (Fortinet) that ...
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1answer
2k views

What are the five flag bits in OSPF Hello packet that specify optional capabilities?

What are the five flag bits in OSPF Hello packet that specify optional capabilities? This may be a textbook question and probably less important.
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184 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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51 views

Why does my route-map blackhole some equally specific routes? [closed]

I have a challenging situation. I have two routers, in VIRL, sharing routes via BGP and OSPF I am attempting to remove the "network 0.0.0.0 255.255.255.255 area 0" from my OSPF process. I have tried ...
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1answer
230 views

Connecting eBGP and iBGP routers in Quagga

I am trying to run intra and inter-domain routing using Quagga. I like to announce a prefix from AS7 and I like AS6 receive it and send it to AS2(as shown in the attached topology). I know for intra ...
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1answer
308 views

High Availability for ISR 4431 IPSec VPNs

I have the following lab setup in GNS3. R1 & R2 are VPN endpoint at my datacenters and R3 is simulating a remote site. What i'm trying to accomplish is having one tunnel from R3 to the ...

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