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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29 views

OSPF type-5 LSAs for routes without gateway [on hold]

Suppose I have a few Linux/Bird "routers" running OSPFv2 over GRE, and one of them has a tun interface created by OpenVPN. Since 'tun' interfaces are layer-3, from the kernel's point of view these ...
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45 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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48 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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38 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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33 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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99 views

Routes stopped redistributing through OSPF

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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2answers
478 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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66 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
84 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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21 views

How to force client side HSRP interface to go into standby when internet is not reachable [duplicate]

I have a VIRL setup in which the client router is connected to a client switch that connected to two provider switches that have HSRP configured for the client gateway. The two switches are in an OSPF ...
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87 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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98 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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77 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
64 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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44 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
101 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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40 views

Basic connectivity won't work in Packet Tracer

I've been redoing this multiple times and I'm sure i configured it correctly, however there is nothing happening at all. It's just a basic network with 3 routers and OSPF configured. Here are the ...
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59 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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1answer
32 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
76 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
70 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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1answer
34 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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1answer
63 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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65 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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2answers
61 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
93 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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44 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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29 views

Multiaccess link show two Designated Routers in area 0

I have 4 cumulus routers setup 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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128 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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1answer
60 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
76 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
337 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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57 views

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

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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1answer
229 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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230 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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114 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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2answers
499 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
301 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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3answers
877 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, ...
4
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1answer
171 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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54 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
122 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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1answer
47 views

Is the Backbone Area connected AS Area are through one router?

I am studying Networking, and I find the Area 0.0.0.1, Area 0.0.0.2 connect to the Backbone Area is through one path, is it means only through one router(or say not more)? we often hear that the ...
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2answers
74 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 ...
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1answer
218 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
908 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
155 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
362 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
244 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
3k 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 ...