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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25 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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24 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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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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59 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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20 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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63 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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166 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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85 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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87 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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26 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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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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52 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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41 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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51 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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41 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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35 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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130 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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97 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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81 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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82 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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135 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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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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46 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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191 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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93 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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134 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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323 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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123 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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141 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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70 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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61 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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1k 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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119 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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50 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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200 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
232 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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48 views

Which device initiates the data exchange in OSPF (is it the master device or slave)?

I want to know which device initiates the data exchange in OSPF protocol (master device or slave device).
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64 views

How to transition an unauthenticated OSPF area to an MD5 authenticated area on a Cisco?

I currently have an existing OSPF area that has neighborships and is exchanging routes, but has no authentication mechanism. Is there a way to transition it to an MD5 authenticated area without ...
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118 views

In OSPF, can I have an NSSA router act as the DR for the ABR router in area 0?

I have a router in an NSSA area attached, via an ABR, to area 0; this is done through a broadcast link with a point-to-point address (31 bit prefix), so there are basically only two routers on this ...
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100 views

In OSPF does a DR consume more resources than a BDR?

What is the best practice in conserving router resources? Should a single ABR router be the DR for all areas? Will that have a negative impact on the resources, or would it be better to let other ...
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1answer
250 views

Configuring BFD for OSPFv3 between IOS-XE and JunOS

i need to implement BFD on a IGP Link with dual-Stack OSPFv3 between an IOS-XE device (ASR903) and a Juniper MX480. i'm running BFD for Dual-Stack OSPFv3 members on many links between IOS-XE and IOS-...
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49 views

How does the OSPFv2 and OSPFv3 instance learn the neighbor IP address?

For example, when I view the output of show ospf neighbor detail or show ospf3 neighbor detail in Junos, then I can see the IP address of the neighbor device interface. This field indicates the IP ...
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33 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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238 views

OSPF over IPIP tunnel doesn't work for CSR 1000v in AWS

I literally have the following topology shown in the figure below. I have 4 VPCs, each VPC has 3 subnets (1 for the VM instance and the other 2 for interfaces). Each VPC hosts a Cisco CSR 1000v in ...
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103 views

My OSPF Multi Area Topology is not reliable

I made an ospf multi area topology, but it's inconsistent. At times, host from the A area could ping to hosts in other areas however, sometimes otherwise (failed to arrive). Whenever I tried to do a ...

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