Questions tagged [ospf]
For questions about OSPF. Open Shortest Path First (OSPF) is a link-state routing protocol for Internet Protocol (IP) networks.
344
questions
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25 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 ...
1
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1answer
43 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 ...
1
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1answer
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 ...
0
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1answer
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....
0
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1answer
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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0answers
98 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, ...
8
votes
2answers
477 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 (...
0
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2answers
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 ...
1
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1answer
83 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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0answers
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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1answer
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.
3
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3answers
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 ...
1
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2answers
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 ...
1
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1answer
63 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 ...
0
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1answer
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 ...
1
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1answer
100 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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0answers
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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0answers
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 ...
0
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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 ...
0
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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 ...
3
votes
1answer
69 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 ...
3
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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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2answers
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 ...
2
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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 ...
2
votes
1answer
92 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-...
3
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1answer
43 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 ...
1
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1answer
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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0answers
126 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 ...
2
votes
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 ...
2
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1answer
334 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
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 ...
2
votes
1answer
225 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 ...
1
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3answers
229 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 ...
2
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0answers
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
496 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 ...
1
vote
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 ...
7
votes
3answers
871 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
votes
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 ...
2
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0answers
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-...
1
vote
1answer
121 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 ...
1
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1answer
46 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 ...
4
votes
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 ...
1
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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
897 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 ...
0
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1answer
152 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 ...
1
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1answer
361 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 ...
-1
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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:
...
3
votes
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 ...
