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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Interior vs Exterior Gateway Protocols
I'm new to Networking and I was reading about the Interior and Exterior Gateway Protocols ,but i couldn't understand some points , as stated in a reference:
IGPs are designed to work in private ...
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OSPF Equal Cost Load balancing with External E2 routes
I am learning about OSPF external routes (E2) and I've decided to lab them up. Here is my topology.
192.168.1.0/24 and 192.168.2.0/24 are just loopbacks configured on the ASBR.
My book states that ...
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Doesn't OSPF Have Auto Summarization?
I asked AI if there is a command in OSPF for auto summarization like RIP and EIGRP. Here is the answer:
"No, OSPF does not have a command like RIP and EIGRP that enables or
disables automatic ...
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Why is the EXSTART state necessary in OSPF?
Many OSPF sources mention that during the EXSTART state, routers communicate and decide who will be the master and slave based on their RIDs (the router with the higher RID becomes the master).
...
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OSPF ECMP on /32 - consequences on EVPN-BGP
Afaik OSPF ECMP is based, one of the two options, on the destination IP address.
Hence if the OSPF advertised route is a /32 basically I wouldn't take advantage of the ECMP.
Now the question: in the ...
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How to permit ospfv3 packet in ipv6 access list?
In Packet Tracer, I have a private network with 5 different VLANs and inter-vlan routing enabled on R1. These are connected via an edge router to an ISP. On the interface S0/0/0 of R1 in direction in ...
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Cisco Packet Tracer - OSPF network variable length subnet
I'm not sure if I going crazy or not. I try to configure an ospf network:
(conf)#router ospf 1
#network 10.73.90.80 0.0.0.63 area 0
I then type show running and it reverts to 10.73.90.64 0.0.0....
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What Happens If A Router Added To The Wrong Area Instead Of The Area 0?
Considering This Topology:
Which is a part of the Practical Networking youtube educational channel, we can see three areas.
The teacher said that all traffic should go through Area 0 to keep a Hub ...
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What Is The Difference Between Using Wildcard Mask In EIGRP And In OSPF?
I noticed that in the CBT learning videos, a lot of teachers ignored using the wildcard mask when configuring the EIGRP, however, they always used it when they configured OSPF. I looked on the ...
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What Is The Difference Between OSPF Neighbors And Directly Connected Routers?
I have read somewhere that:
OSPF router’s neighbors are usually the routers directly connected to
it through its interfaces, from a layer-3 perspective. However, there
are some exceptions, such as ...
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Why do typical spine-leaf architectures have one border leaf instead of all leafs having an uplink?
In all spine leaf architecture explainers I've seen I've come across the concept of the border leaf which is used as the connection point of the entire clos network to an upstream router, be it either ...
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The purpose of last database description packet sent by the slave router during adjacency process
I've been learning OSPF adjacency process using packet tracer. The topology is a simple point-to-point network - two routers are connected with ethernet cable(fastEthernet 0/0 on both ends).
Here are ...
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Hide private IP address
DS has 7 VLANs and 7 DHCP pools respectively. There are 3 trunk links to 3 access layer switchs to share VLANs. Its VLAN interfaces and DHCP pools:
ip dhcp pool vlan10
network 192.168.10.0 255.255....
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In router's config, why do I need to advertise the directly connected network?
I have learned that, in routing config, a router must advertise all of its networks.
For example, in this topo:
Router A need to network 192.168.1.1 0.0.0.255 and network 100.1.1.2 0.0.0.255
But why ...
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Is TCP used for data transfer after building the routing tables (using OSPF protocol)
I am trying to understand how Data (video, image, ...) is sent over the network, and what are the protocols and different processes involved. We know that OSPF (L3 protocol) does not use TCP or UDP, ...
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OSPFv3 Convergence Issue between OPNSense & Cisco Router
I have been digging around the internet and have been trying to get IPv6 up and running on my lab. Here is my current layout:
I have been trying to get OPNSense and the Cisco 1900 router to give each ...
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How to properly configure OSPF protocol?
I have this simple 3 router network that I need to configure the OSPF for, when using two routers every thing works fine and i can ping but when I add the third router nothing works
left router
...
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how does OSPF work with different subnets and is it slower?
I'm having the following topology:
[router A] port1===port1 [router B] port2===port2 [router C]
subnet 1 on router A and B via port1
subnet 2 on router B and C via port2
Now all routers are in area 0,...
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How does OSPF know the cost of the interfaces between the router and the destination network?
So OSPF calculates and adds the best route to its routing table. The best route is the one with the smallest metric - cost.
However, how does an OSPF enabled router know the cost of the interfaces ...
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Does the order of Link State Advertisement packets in OSPF matter?
Does it matter in what order an OSPF router receives LSA packets while reliable flooding is being performed in its area?
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A question about DR/BDR routers in OSPF
About OSPF DR/BDR Routers.
If a link like the one on the top left corner goes down, the router will let the DR and BDR know by generating a Link-state Update Message and sending it using the ...
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Layer choice for OSPF
When designing the OSPF protocol, the designers choose to place it on top of the IP layer but why isnt it used above the data link layer? what would be the drawbacks?
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OSPF areas with two ABRs
With the following hypothetical network (each link between routers is /31 and configured as OSPF point to point)
Do R1 and R2 need to be neighbors inside area 1 considering their interfaces are all ...
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OSPF area or ABR impact on CPU and RAM consumption
I have two statments on OSPF, are they correct?
1- If I split a single area OSPF to an OSPF domain with area 0 and area 1, and there is just one ABR between area 0 and area 1, The load on CPU will ...
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Configure Inter-VLAN and OSPF - FIXED!
Hi guys thank you for your all answers!! I finally solved it. The IP is overlapping because of duplicate vlans. I replace same vlans to new vlans and it worked.
How can I make my VLAN connected to the ...
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OSPF routes are not advertised
routers with ASBR2 connecting to AREA 0 and 10 and ASBR1 connecting to area 0 and 20, there's no entry of routes in R1's routing table, help me out
R1#sh run
Building configuration...
Current ...
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When would we use more than 1 dynamic routing protocol?
I am learning about different dynamic routing protocols and I've learned that each dynamic routing protocol has an AD assigned to it which indicates the trustworthiness of the learned route from that ...
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OSPF - How does slave know what to send LSR to when DBD is not shared by the master
Consider a topology where R1 and R2 are connected.
R1 has following networks. 192.168.1.0/24 192.168.2.0/24 192.168.100.1/32
R2 has following networks. 192.168.2.0/24 192.168.30.0/24
192.168.2.1 and ...
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OSPF unadvertised routes are reachable
My network consist of 4 routers:
R1(with loop back network of 11.0.0.0)
R2(with loop back network of 12.0.0.0)
R3(with loop back network of 13.0.0.0)
R4(with loop back network of 14.0.0.0)
R3 is my ...
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Setting an OSPF router in one area that doesn't see other areas
Could an OSPF router be configured so that it can only see its own area LSAs and does not accept LSAs from other areas? (For example, if it is in area 2, its routing table just shows routes in area 2, ...
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Why is the highest IP address taken as Router ID by default in OSPF?
I know there are 3 ways for Router ID to be selected in OSPF but my question is specific to the auto-select of ID on basis of highest IP address (loopback or non-loopback). Why is the highest IP ...
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Does OSPF acknowledge DBD packets with an LSAck?
I don't see any LSAck for DBDs being sent out in this sample pcap:-
https://www.cloudshark.org/captures/e7dbbc860456
Does OSPF really send LSAck upon reception of DBD packets ?
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Ospf multicasting with two different group
Suppose I have one ospf network where two multicast group exists. And some routers is ospf which belongs to one group or multiple group (Like: routers E, H) and router is layer3 router (Like: ...
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CCNA | OSPF | What differences can exist between two processes of a single routing protocol?
It is my understanding that a process is a specific-instance of a routing protocol. The process-id is a symbolic representation of a unique instance of that RP within a router.
If that's the case, ...
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CCNA / OSPF / Area / Alternative Definition
Can another definition for an OPSF area be: A multicast domain within a larger autonomous system that is primarily subject to a single LSDB (topology database)?
//edit
I'll modify my definition soon.
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Why can't I ping from a pc in one OSPF area to a pc in another OSPF area after configuring each neighbouring network?
So I have an exercise with this topology:
I have configured all the OSPF networks on each router and I made every g0/0 interface (except for the ABR in the middle) a passive interface.
However, I ...
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OSPF Theory Question | Area Design
I know there are many assumptions to this question but:
Would it be possible to simultaneously configure all area x routers through something like SNMP for the purpose of merging with another area? If ...
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OSPF Theory Question | Topology Changes | LSU Flooding
Could you create a script on an ospf router that enable/disables interfaces randomly, and faster than time neighbor routers update their LSDBs, making a network that's constantly flooded with LSU ...
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Trying To connect Router4 to internet
In the picture, I have a part of my topology. The concept is that I am trying to configure OSPF in my network. Internet is a nat cloud module. The routers are all iosv routers.
ISP 1 has the following ...
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Routing for same subnets in remote sites
Is it possible to have interVLAN routing with router on a stick topology, but with remote sites communicating via OSPF? In the diagram below, I can ping PC1 from PC0. What I want is to ping PC2 and ...
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Why does redistributing ospf in rip change the path of all routers on the rip network that are not directly connected to the router that redistributed
I have three routers connected to each other. Each has a subnet that it uses (eigrp, ospf, rip) as shown in the figure
I managed to redistribute EIGRP and OSPF, this works perfect. But when I try to ...
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What does the OSPF RFC mean when it says "The master sends the first Database Description Packet"? [duplicate]
I'm trying to reconcile what I've read about the OSPF Master/Slave process, with what the RFC says, with what I'm seeing on the wire.
Everything I've read implies the Master starts the LSA exchange by ...
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How to view or change OSPF LSA max-age time in Cisco IOS?
Is there any way of viewing or changing OSPF LSA Max-Age time in Cisco IOS?
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Designing Workaround for Missing IPv6 Support (OSPF or BGP)
We have a pair of Ruckus (Brocade) ICX 7750s that we use as our core routers. They currently handle a BGP connection with our ISP and then use OSPF for internal routes. Our ISP is finally going to ...
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Passive interface default - issue
I was trying to configure ospf router, I have a router connected to FW in G1/0/10 and mpls router connected g1/0/1, when i typed passive interface default in the ospf router i lost all connectivity ...
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Meaning of import or export in Juniper routing policies
What exactly is happening to the junos ospf protocol and junos routing instance when one executes these commands?
set policy-options policy-statement POLICY-STATIC term TERM-STATIC from protocol ...
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OSPF and RIPv2 behaviour with route through switch
I have 2 questions, both relates to routing protocols.
How route/path looks like when there is L2 switch inside path. I mean with turned on either RIPv2 or OSPF. To clarify I must say there are 2 ...
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OSPFv3 Authentication IPSEC SPI/Logging issues - Can you filter out logs?
I'm running into a problem with our Cisco ASR-1002HX and ASR-1006X. I have a mix of Juniper and Cisco routers all configured exclusively with IPv6. All of our routers are in the same ospfv3 area 0. We ...
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How does OSPF work on point-to-point Ethernet interface (i.e, 2 routers connected by a cable)
OSPF RFC describes two different modes of operation of OSPF for (1) point-to-point and (2) broadcast networks (and others).
The operation on (2) involves selecting designated router and backup ...
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Why does OSPF use flooding despite using multicast?
We know that flooding is only possible in layer2 switch. But in OSPF router in layer3 uses flooding with multicasting. Suppose we have one router in OSPF uses multicast address 225.0.0.9. If router ...
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