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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How is the next-hop for an OSPF route chosen if there are multiple equal paths?
Let's say, that a Juniper router learns a 10.10.10.46/31 prefix from two different OSPF routers:
root@r1> show route 10.10.10.46/31 protocol ospf
inet.0: 10037 destinations, 50063 routes (10034 ...
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OSPF - is the Designated Router the same thing as the Master Router?
Is it possible, to have a DR as a Slave Router?
So here is my knowledge:
The DR and the BDR are elected based on priority and then highest RID in an area, so every router can communicate with the DR ...
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Is it possible to accomplish Cisco IOS "prefix-suppression" functionality in Junos?
I have a network of three Juniper routers:
ge-0/0/* and lo0.0 interfaces are in OSPF area 0. My goal is to have only the loopback addresses in OSPF, but as seen below, the network 10.7.0.4/31 used ...
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OSFP anycast route different area
So.. lets pretend i need to advertise a route in anycast to the backbone, obviusly same route that in this case is 192.168.1.111 .
Can be a problem if the routers that advertise that route to the ...
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How can I implement BGP between two routers that have already been configured with different routing protocols?
I have two different AS with different IP ranges and subnets, and the first router stack is running RIP, and the second one is OSPF. I want to configure BGP between "Router-PT Router23" and &...
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CCNA OSPF Loopback as the router ID
FYI, I am studying for the CCNA and new to this.
The scenerio, 2 routers R1 and R2.
R1 Loopback IP as 192.168.0.1
R2 Loopback IP as 192.168.0.2
Using the loopback IP's as the router ID.
I provisioned ...
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How to configure OSPF to create desired routing paths?
Is there any way to assign OSPF cost so that when is traceroute 147.147.11.98 from R1
it goes like R1->R4->R5->R2
and when I traceroute 147.147.11.98 from R5
it goes like R5->R4->R1->...
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How does OSPF sense the physical media?
For different physical media types, OSPF behaves differently about electing a Designated Router or not. For example, non-multiaccess media links such as serial Point to Point do not need election for ...
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Redistribution Loops and Route Tagging
I've read that when we configure multipoint redistribution, it's a good idea to tag our routes to prevent them from being advertised from Protocol 1 - Protocol 2 - Back to Protocol 1.
Source: ...
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Will an OSPF route in IOS be preferred over a static route? (It isn't Floating Static)
For the network topology attached in the image, a static route is configured with ip route 10.10.10.0 255.255.255.252 Ethernet0/0. Referring to the Topology and the output from the show ip route ...
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OSPF Advertise only loopback not transit VLAN
I have this topology:
and this configuration:
R1
interface Loopback0
ip address 10.0.0.1 255.255.255.255
ip ospf 1 area 0
interface GigabitEthernet0/0
ip address 192.168.0.1 255.255.255.252
ip ...
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Conflicting opinions for route aggregation [duplicate]
I am a student and I came accross this question:
An ABR in OSPF has in its range networks 10.0.8.9/24 to 10.0.21.0/24. how can it summarise the networks? not necessarily in one prefix.
What we ve ...
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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 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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