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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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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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19 views

how to redistribute using EIGRP instead of my shortcut way [closed]

I used these commands to redistribute: router ospf 1 redistribute rip metric 500000 subnets exit redistribute ospf 1 metric 0 end I want to the redistribute using the eigrp?
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34 views

OSPF using a new MAN network [closed]

I am working on a MAN network setup. It is not live currently, we are using IPSEC VPN tunnels back to the main office for the remote offices of ours. I am wondering how to setup from scratch OSPF to ...
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1answer
36 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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1answer
37 views

OSPF inter-area traffic - not so direct after all

a) Can I confirm inter-area traffic will be routed towards Area 0 / Area 0 will be the transit network for all inter-area traffic? b) Consider the diagram below q1) Does R1 receive Type 3 LSA for ...
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1answer
30 views

%OSPF-4-ERRRCV: Received invalid packet: mismatch area ID, from backbone area must be virtual-link

I have a topology like this: this Router0-1's Gig0/0/0 ip: 10.0.12.1/24, the Router0-2's Gig0/0/0 ip: 10.0.12.2/24, Gig0/0/1 ip: 10.0.23.2/24, this Router0-3's Gig0/0/0 ip: 10.0.23.3/24, at ...
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0answers
24 views

Whether the OSPF ABR Router's loopback network should announce to Backbone Area? [on hold]

The OSPF ABR Router whether its loopback network should announce to Backbone Area? the upper snapshot shows the C,D,E are ABR Routers, if everyone has its own loopback networks, I want to know ...
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15 views

Is there any rule for select the Net Link's ADV Router? [duplicate]

I have a topology like this: show ip ospf database OSPF Router with ID (2.2.2.2) (Process ID 1) Router Link States (Area 0) Link ID ADV Router Age ...
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1answer
42 views

What's the definition of Router Link and Net Link?

When I show the ospf database: Router2#show ip ospf database OSPF Router with ID (2.2.2.2) (Process ID 1) Router Link States (Area 0) Link ID ADV Router ...
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3answers
75 views

Why the OSPF router do not have neighbor?

I have two Routers in the Cisco Packet Tracer: Router2-1, Router2-2, Router2-3 all have their own loopback 0 with IP address 1.1.1.1, 2.2.2.2, 3.3.3.3. I only launched the OSPF progress in the ...
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53 views

OSPF behavior for redistribute routes

I have 2 equal cost path links between PeerA and PeerB and all its interfaces are participating in the same OSPF area. When i redistribute a static route (172.16.2.0/24) from PeerB to A, does the ...
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23 views

Zebra: Redistribute BGP over OSPF [on hold]

I am using netkit to simulate 2 AS: One with 3 nodes interconnected using OSPF. Other with 1 node using static routing. I interconnect the AS using BGP. Connection intra-AS is OK, but I am failing ...
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2answers
67 views

How to assign all interfaces in one router to OSPF backbone area?

Is there any command to assign all interfaces in router (CISCO 2691) to OSPF backbone area? I was using this command for each interface. network address wildcard-mask area area-id Where wildcard ...
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1answer
49 views

Quagga - Configure 3 routers using OSPF

Hi I'm trying to use quagga to connect 3 routers but the middle one doen't complete the path that a trace route command would do even though it knows where the target address is. It seems that ...
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1answer
212 views

OSPF and its use of Multicast

When it comes to OSPF and its use of multicast, am I correct in believing that IGMP forwarding and an IGMP querier is still required within the local segment? My understanding would be without this, ...
3
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1answer
53 views

When do multiple routers connect to the same switch (ie for DR election process)

When studying for the CCNA we are presented with the 3 tier Cisco model below. Then when we discuss routing protocols there are many images where these routers are connected in a switch and thus need ...
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0answers
49 views

OSPF peering not forming when authentication is enabled

OSPF peering between two of my routers went down 2 days before. After troubleshooting, I removed the authentication commands from both devices GRE tunnel interfaces ip ospf authentication message-...
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1answer
35 views

OSPF DR and ABR relationship

I know the DR/BDR and ABR are of course separate concepts and serve different functions, but in many cases is the ABR router for a given area also made to be the DR? Or would the DR be more often an ...
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2answers
67 views

Routing Table Eligibility

I have an architecture which is that each remote site has 2 Dialer interfaces dialling into a virtual-template core which authenticates the sessions and applies attributes from a RADIUS server. OSPF ...
1
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1answer
64 views

MultiLayer Switch to Ping different Switches and routers under different VLANs [closed]

Hey Guys, So this is basically a small design of a made up university which has 3 campuses( the 3 routers).Each connected to 1 College(Switch) and each college connected to 3 other Schools(switches) ...
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2answers
166 views

Prevent OSPF routes advertised by other routers from entering the routing table?

I have a fairly complicated scenario that I've managed to duplicate with GNS3. Please see the attached image. In this scenario I have four "Branch Offices" each with their own router connected to ...
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1answer
53 views

Prevent OSPF routes from one network from being redistributed to the rest of the network?

Synopsis: Network A needs to be able to use a static default route to Network B via a local connection (G0/0/3). Network A does NOT want to route ANY Network B addresses through the rest of its ...
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1answer
156 views

Cisco ASA context OSPF configuration issue

I've two cisco ASA configured in active/active HA. ASA is connected to switch with port-channel. Switch configuration: interface Port-channel47 description ASA2 switchport mode trunk switchport ...
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2answers
135 views

the difference between RIP and OSPF [closed]

I was working with CISCO and to create a path between switches my teachers told me that I can use 2 types of protocols, but they did not explain to me what differences there are between the two: ...
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1answer
1k views

How to flush route cache in fortigate

Is there something like route cache on fortigate like in linux? How can i clear this cache? I have some problems with OSPF, after adding or changing redistributed network. Foritgate show routes ...
4
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1answer
71 views

Question about OSPF and Database Descriptions

After the adjacency as been formed between two routers, a master-slave-relationship between two routers is formed too, where the master begins to send Database Description (DBDs). My question is: ...
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1answer
57 views

Why does OSPF function on Network Layer whereas RIP functions on Transport Layer?

As far as I know, OSPF creates its messages directly at the network layer, whereas RIP function on UDP. Their function is pretty similar, so why is there such a difference in their messaging practice?
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1answer
319 views

Broadcast,multicast and unicast in OSPF

In OSPF, routers from down to full state,what's kind of networks(broadcast multicast unicast) used per state to exchange information? I always heard 224.0.0.5 and 224.0.0.6 these two address, and was ...
3
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1answer
138 views

OSPF Area Design

Have a hub and spoke design where each Branch has a single router with a WAN connection to DataCenter1 Hub and another WAN connection to DataCenter2 Hub. There is no OSPF running elsewhere in the ...
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3answers
902 views

Configuring OSPF on two directly connected routers which are in different areas

I want to configure OSPF on the topology below. The problem is when I connect two routers to each other and when I config one router to area 0 and another one to area 1, they don't see each other as ...
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1answer
277 views

Why OSPF E1 and E2 exist?

I know the difference between E1 and E2 metric-types. I know the preference level given to those routes. I know difference between Metric and Forwarding Metric and how it works. What I don't ...
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2answers
325 views

OSPF on tunnel interfaces

Can I keep different tunnel interfaces in different OSPF areas. Keep in mind that the physical interface is going to be the same
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2answers
154 views

How does a route-map applied as outbound on a neighbor sees the redistributed ospf routes into bgp? Local or external?

Here's my scenario: Redistribute ospf routes into bgp Create a route-map that matches on route-type=local and modifies the nexthop (to 4.4.4.4 for example) Assign this route-map as outbound routemap (...
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3answers
169 views

Cisco Vlan block access

So I have 2 core switches and 1 access switch, I have the vlans 1, 10, 20, 30 and 100. Vlan 10 is voip and what I would like to do is stop anyone on the other vlans from being able to see that subnet, ...
4
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1answer
480 views

Why does EIGRP have lower Administrative distance than OSPF?

I have given the following network diagram and been told that, Since EIGRP has a better (lower) administrative distance than OSPF, the router on the far left will use the EIGRP path and publish ...
2
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1answer
207 views

BGP with OSPF configuration question

ISP - Sending default route to sw1/2 via eBGP sw1 - config router ospf 100 network 0.0.0.0 255.255.255.255 area 0 default-information originate always ! router bgp 100 bgp log-neighbor-...
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1answer
695 views

nexus ospf network statement missing

In old school IOS we used to do router ospf 1 network 0.0.0.0 255.255.255.255 area 0 But in Nexus switch i am not seeing any command or related doc, how do i announce my subnet in ospf in nx-os My ...
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2answers
241 views

OSPF - Default route doesn't get advertised to all areas

I am trying to find the reason why R1 doesn't have the default-route, propagated and generated by my Internet-PAT-Router, in his routing-table. The weird thing is, that R2 actually has an entry for ...
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1answer
273 views

How to implement Layer 3 (OSPF, IS-IS) link redundancy?

I think this kind of topic may be a course basic, but I'm still have a lot of technical doubts on how to implement redundant links on Layer 3, for example: -In order to use dual homing for a remote ...
3
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2answers
350 views

vPC traffic flow question

This is going to be new network in my datacenter and i have question related vPC, as you can see i have A1/A2 switch (L3/L2 routing) in aggregation layer and C1/C2 switches for Core (L3 routing). I am ...
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1answer
145 views

Is it required for an ABR to be connected to area 0?

The question "why is it required for all the areas to be connected to area 0?" is answered many times on the internet. However, I could not find an answer to the above question. Please refer to the ...
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1answer
236 views

OSPF Area Multiple Subnets

Is it possible to have multiple subnets in one OSPF area? Everything I can find so far points to the answer being 'No', however I need to know for sure if it's possible or not. Our current setup is a ...
4
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1answer
84 views

OSPF - networks/links don't get advertised

In my Multiarea-OSPF configuration I can ping my neighbor, but nobody which is more than one hop away (for instance ABR2). Also traceroute just shows "1 * * * - 2 * * * - 3 * * *" Can ...
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2answers
499 views

OSPFv3 (newer commands) not working in Cisco Packet Tracer

The command router ospfv3 1 is not working in the Cisco Packet Tracer (Router: 2811). Does it work somehow or are the IOS version just not up-to-date?
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2answers
382 views

OSPFv3 - Sample configuration (Dual Stack IPv4 and IPv6) - Cheat Sheet

When configuring OSPFv2 on a router, you type in router ospf 10 router-id 1.1.1.1 network 10.0.0.0 0.0.0.3 area 0 for example. That way the network can be advertised per LSAs. But in OSPFv3 it ...
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2answers
203 views

Cannot see the differende between distance-vector and link-state

At link-state routing protocols each router advertises every link he knows about to the next router, which again advertises his links and so on until every router knows all links in his area. So every ...
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1answer
71 views

Clarifications about RIP and OSPF

What (I think) I know: RIP uses a distance vector routing approach, where each node sends to its neighbors the number of hops one should take to get to other routes if one "started" from that ...
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2answers
320 views

Will an EIGRP route be chosen over an OSPF route regardless of metrics?

I am sure this has been asked SOMEWHERE but I can't find it anywhere. Question is simple: Will R1 chose the EIGRP route to R4 over the OSPF route, even though the OSPF route is clearly the better ...
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1answer
244 views

Struggling inbound and outbound traffic engineering to/from iBGP peers at different POPs

We are a managed service provider running a small sized network in a single datacentre in Sydney. We've recently deployed a new POP inter-state in Melbourne (both are on the east coast of Australia), ...
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3answers
2k views

Why does MPLS need an IGP (like OSPF) in order to work?

I saw a network using MPLS, BGP and OSPF as main network protocols. I understand that BGP was used to exchange traffic with another AS, and OSPF was used as Internal Gateway Protocol. So, why to use ...