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For questions about OSPF. Open Shortest Path First (OSPF) is a link-state routing protocol for Internet Protocol (IP) networks.

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design - Cisco ACI and Nexus 7ks - best choice OSPF or EBGP

We have two data centers as shown in the picture. Data center 1 and data center 2. At each data center 1) Nexus 7ks have 3 VDC's configured . WAN_VDC is connected to Cisco ACI using L3 Port ...
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40 views

GNS3 - BGP and OSPF redistribution

Hello Guys, referring to the picture, I have configured ebgp between R1 and ISP 1, and R2 and ISP2. iBGP has been configured in a full mesh internally on top of OSPF. All neighbors are up and peered ...
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1answer
13 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
45 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
33 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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64 views

OSPF behavior on VRRP groups

I have OSPF area showed on pic. A, B, C - vyos, D - edgeos. Digits - ip ospf cost on interfaces. Master, backup - vrrp roles. I expect that ospf creates route to CD-network through C, but on A and ...
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49 views

OSPF stuck in Exchange state - Point-to-point setting is ignored?

I am participating in the DN42 project. In the scope of this project, i have my own (virtual) AS. It contains the IP range of 172.23.211.0/24, and currently two hosts. A server, with the IP 172.23.211....
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32 views

How to configure Check Point Firewall BGP and OSPF?

I Need assistance with configuring BGP on a Check Point firewall. It receives only the default route, and I want to redistribute that into OSPF. If the circuit goes down, then default route is ...
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2answers
84 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
27 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
88 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
82 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
608 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 ...
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1answer
67 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
48 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
214 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 ...
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1answer
93 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
627 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
166 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
232 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
107 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
133 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, ...
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1answer
322 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 ...
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1answer
160 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
502 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
161 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
191 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 ...
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2answers
283 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
106 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
186 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
383 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
293 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
184 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
54 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
219 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
209 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
1k 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 ...
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1answer
62 views

OSPF packets type - link failure and new adjacencies creation

Regarding an OSPF topology, when a link failed, some new LSA will be send, and flooded by all routers (or DR) in the area. What is the type of packet ? Link-state Update which contain these LSA ? ...
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2answers
197 views

OSPF loop avoiding

I would have a question regarding OSPF, when a topology is being created, how the LSA loop risk is prevented ? If you have X router the LSA should be routed over all the the network and how a loop is ...
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4answers
177 views

OSPF Link State Advertisement

As i see, there are different packets in OSPF. Hello packets DBD packets LSR LSU LSA(Acknowledgement) DB packets contain LS Advertisement, LSR contain LSA ID and Link State Type, LSU contain LS ...
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1answer
204 views

Communication between BGP and OSPF routers

I will start with a scenario. Please excuse me if its a low-level question. Lets say there are 2 AS, AS 100 and AS 200. *In AS 100 there are 3 routers R1,R2 and R3 running OSPF and RB1 and RB2 running ...
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3answers
209 views

OSPF LSA type 3

This is what I know about LSA types from what I've learnt. LSA type 1 is circulated inside an area and doesn't get to other areas. LSA type 3 is sent from one area(From backbone to non-backbone and ...
2
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1answer
62 views

OSPF DR election

From what I know, DR and BDRs are elected in an area which has an Ethernet segment. So what happens, if the area has a combination of both p2p(Mesh for example) and also an Ethernet segment which has ...
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1answer
77 views

How do we interpret LSU in OSPF?

This is a kind of a very basic question in OSPF packet exchange. What are these kinds of link in LSU - Stub link, PTP and again Stub link. What I am trying to achieve here is to understand how a ...
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1answer
37 views

Possible to do a port-channel and STP with three 10Gbps fibre interfaces?

I have two sites that I'm planning to interconnect via three circuits carrying layer 3. They will be presented via fibre. The bandwidth of the lines will be: 1Gbps, 1Gbps, and 2Gbps. Each SFP will ...
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2answers
786 views

Why is ospf to bgp redistribution and simultaneous bgp to ospf redistribution dangerous?

I am referring to this question, where OP apparently fixed his issue by redistributing ospf in bgp and vice-versa on the same router. The user Sebastian warns that this is a dangerous practice. We ...
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1answer
93 views

Is this a valid supernetting range for OSPF range command?

Is it a right way to supernet/range in OSPF for the following network address? area 0.0.0.x 10.128.0.0 255.255.255.0 How 10.128.0.0 can have a subnet of 255.255.255.0, e.g. /24? Is this a right ...
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1answer
128 views

Why does OSPF use flooding instead of broadcasting?

In flooding, we send unicast/multicast frames to all the routers in the network, whereas in broadcasting, we have a broadcast address by which we send packets to all the routers. In OSPF, "Router ...
3
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2answers
159 views

OSPF Issue, redundancy between P2P (MPLS) and Firewall

I drew a diagram for the network to make it easy to understand my network issue. Site B,C and D communicate through MPLS and in case of failover they communicate through VPN tunnels. Site X ...