Tagged Questions
For questions about OSPF. Open Shortest Path First (OSPF) is a link-state routing protocol for Internet Protocol (IP) networks.
0
votes
0answers
35 views
+100
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
votes
2answers
59 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
234 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 ...
4
votes
1answer
64 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: ...
1
vote
1answer
46 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?
1
vote
1answer
115 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 ...
3
votes
1answer
77 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 ...
4
votes
3answers
491 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 ...
3
votes
1answer
114 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 ...
3
votes
2answers
175 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
4
votes
2answers
86 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 (...
2
votes
3answers
98 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, ...
4
votes
1answer
223 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 ...
2
votes
1answer
123 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-...
1
vote
1answer
333 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 ...
3
votes
2answers
130 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 ...
-1
votes
1answer
134 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 ...
3
votes
2answers
228 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 ...
1
vote
1answer
70 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 ...
0
votes
1answer
127 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
votes
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 ...
3
votes
2answers
315 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?
1
vote
2answers
225 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 ...
4
votes
2answers
177 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 ...
2
votes
1answer
50 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 ...
1
vote
2answers
153 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 ...
5
votes
1answer
182 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), ...
3
votes
3answers
904 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 ...
1
vote
1answer
55 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 ?
...
3
votes
2answers
163 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 ...
1
vote
4answers
149 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 ...
1
vote
1answer
178 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 ...
1
vote
3answers
157 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
votes
1answer
61 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 ...
0
votes
1answer
70 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 ...
0
votes
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 ...
1
vote
2answers
633 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 ...
1
vote
1answer
90 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 ...
1
vote
1answer
103 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
votes
2answers
142 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 ...
0
votes
1answer
76 views
Multicast group membership
Context: Studying for CCNA
I'm trying to understand multicast. I understand it conceptually, but I'm trying to understand implementation. For instance, in OSPF, how is multicast group membership ...
1
vote
2answers
88 views
OSPF Link State Advertisements
I'm confused about how OSPF routers perform LSA to create LSDB.
I suppose, an OSPF router will exchange LSA only with the routers to which it has established adjacencies right?
What adjacencies do ...
2
votes
2answers
312 views
OSPF Configuration: Router ID won't change to loopback address
I am new to this so forgive me for mistakes, but I feel like I am missing something here.
I am trying to use a loopback address as the router ID for Router0 in my network. I am typing in:
Router(...
1
vote
0answers
87 views
OSPF NSSA - Type 7 LSA Metric Changes Unexpectedly
When a new path to an NSSA External (LSA type 7) route is brought up in the topology below, the existing path's cost to that route increments to exactly match the new path's cost. Therefore, both ...
2
votes
1answer
190 views
Implement ospf routing
My topology is
---rtr1-.1---192.168.10.0/24....2.asa1-.2---1.1.1.0/24----.1-asa2-.1---192.168.20.0/24---.2-rtr2
My goal is rtr2 can reach rtr1 via OSPF routing and vice versa
my problem is on ASA, I ...
2
votes
1answer
342 views
Need understanding on Wireshark Capture from LSA update of a link.PCAP attached
Consider OSPF in Area 0 is running on all routers and interfaces.
I advertise a route 223.0.0.1/24 from R4 in the diagram.
PCAP i shared is between r2 and r1 where R2 sends "LS Update"
I'm unable to ...
1
vote
3answers
59 views
How can I forward 0.0.0.0/0 to another router without using static-route command?
hope everything is fine wherever you are.
Now here is my question. I have two routers, R1 and R2. And I want R2 to see 0.0.0.0/0 address from R1. But without using static-route command. Both routers ...
6
votes
1answer
160 views
Router Ethernet port ip no accessible from clients
I have this setup with a hybrid of equipment's from Cisco and Ubiquiti Edge routers and Vyos. My Cisco Nexus configured with HSRP with all the SVI's on 192.168.1.243 as the active on HSRP and SVI's ...
1
vote
2answers
98 views
How can I implement default route along with OSPF?
I read something a cisco. It said OSPF and default route, defaul gateway, arent good friends...
See my architecture below :
Now in that diagram, I'd like PC1 to be able to reach PC2...
To reach any ...
1
vote
1answer
30 views
How to make routing on edges of a router in center of OSPF routing?
Lets says I have 3 routers : R1, R2, R3... All three communicate with OSPF (with athentication and all) ... R1 <--> R2 <--> R3
Now I have R4 on one side of R1 ...
R4 <--> R1 <--> R2 <...
