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What does the notation F0/0 and F0/1 mean in this diagram?

@3iron's answer gave me the hint that I needed. The notation is denoting that there are multiple NIC interfaces on the router in the diagram and it's making reference to this. F0/0 - interface #1 F0/...
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9 votes
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What is the difference between L2TP vs GRE

L2tp and GRE are totally diffrent protocols GRE is a simple IP packet encapsulation protocol. a GRE tunnel is used when packets need to be sent from one network to another, without being parsed or ...
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9 votes

What does the notation F0/0 and F0/1 mean in this diagram?

F0/0 and F0/1 look to be router interface notations to highlight a physical connection into the router from the two respective hosts. Typically they could be: Fa: FastEthernet Gi: GigabitEthernet ...
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5 votes
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Use cases for GRE over IPSEC

Running multicast or multicast based routing protocols does not necessarily require GRE-over-IPsec. "Tunnel based" or "route based" VPN (tunnel mode ipsec ipv4 a.k.a. IPsec Virtual Tunnel Interfaces ...
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5 votes
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How IPsec tunnel mode work without GRE

So what's the difference between GRE+IPsec and IPsec only? In GRE+IPsec the original IP packet is encapsulated in a GRE tunnel packet. The GRE packet is then encapsulated in the IPSec packet. The ...
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4 votes

What problem does GRE solve?

GRE is just a tunneling protocol - its main reason for existence is toplogy hiding/bypass. Some examples include: Tunneling MPLS across a network that may otherwise not support it - MPLS shims are ...
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4 votes

OSPF on tunnel interfaces

Yes, what's important to the router is layer 3 interfaces. You can think of a layer 3 interface as a logical construct, which can be be tied to a VLAN, physical or tunnel interface.
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4 votes
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Scaling VXLAN tunnels in openvswitch

You could solve this by running VXLAN on the hypervisor using software like FRR. That would imply that you run a full mesh BGP setup between your hypervisors, or use route reflectors. Then, you can ...
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4 votes

GRE, guarantee 1500 bytes MTU for end hosts

When there's additional overhead eating into the MTU size, there are three basic approaches: increase outer MTU/frame size, decrease inner MTU, or live with fragmentation. Routers may fragment (for ...
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3 votes
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Regarding front door vrf concept

You have to at least create static host routes pointing to the endpoint IPs of your tunnel to make sure they remain established. Front door vrf is handy if your endpoint is using a dynamic IP address,...
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3 votes
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Why source and destination addresses should match in GRE tunnel?

One simple explanation is that R3 needs to determine which tunnel the packet came from. It's often that there may be more than one tunnel terminating on the same interface on R3. EDIT: More ...
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3 votes

Splitting Data and Voice by creating GRE tunnel for Data, using overhead for Voice

Do not create GRE tunnels - this will appear to your L3 network as two distinct paths to the same site, meaning you'll end up with extra routing complexity you don't need. GRE will also add overhead ...
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3 votes
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Transparent proxy (wccp and squid)

I think Cisco was referring to the interesting traffic is automatically put into a GRE formed tunnel. Which is different than we normally think of when making a GRE tunnel. Usually it has to do with ...
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3 votes
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Gre Tunnel issue

There is not a lot to go on in your output there, but try removing qos pre-classify from the tunnel interface - it may be that you have misconfigured qos settings causing traffic to be dropped.
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3 votes
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qos inside vpn, possible or not ? I read yes and no

Possible? Generally, yes. However, you need to consider the tunnel outside as well. How effective QoS works depends on a large number of parameters only some of which you have control over. QoS ...
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3 votes

GRE over IPSec Transport vs. Tunnel Mode

No, it should not be GRE. In both cases as shown (IPSec tunnel mode and transport mode), it's always IPsec encrypting GRE (and whatever it may contain). Therefore, the outermost header has to be ...
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2 votes

Can different networks connected by MPLS run the same OSPF area?

I think you're looking for the OSPF "Sham-Link" feature. This feature builds virtual OSPF links over an MPLS infrastructure to connect OSPF networks. The feature is available on Cisco and Juniper gear ...
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2 votes

Splitting Data and Voice by creating GRE tunnel for Data, using overhead for Voice

First, if the three sites connect to the data center over WAN circuits with any appreciable latency, layer-2 connections are not a very good idea. Layer-2 must send all the broadcasts across the layer-...
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2 votes

Support GRE tunneling router or firewall

Although GRE is developed by Cisco, it doesn't mean that other vendors don't support it. It's became kinda standard in the industry and I have not seen any single vendor who doesn't support it, ...
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2 votes
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Why specify the source tunnel address?

Often, you may want to use a loopback, since it will never go down, as the source because you may have a backup path to the other end. It is not always the right thing to do to use the exit interface ...
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2 votes
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Two GRE tunnels in one subnet

A 'normal' GRE tunnel is a used as a point-to-point connection. A /30 (or even /31) would be a better use of your subnet space. There also exist multipoint GRE tunnels, such as DMVPN. Here you can ...
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2 votes
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Regarding Gre tunnel encapsulation

Q1: Inner Source: 1.1.1.1 Inner Dest: 4.4.4.4 Outer source: 172.16.0.1 Outer Dest: 192.16.0.2 Q2: The source address is the tunnel source, 172.16.0.1 (for R1-R4 traffic). The inner and outer ...
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2 votes
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Regarding Multicast over the internet

A1: Because normally you need to run PIM protocol in order to achieve end-to-end connectivity for multicast network. PIM doesn't normally run between ISP boundaries. It would be pretty complicated and ...
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  • 1,118
2 votes

Packet flow in GRE Tunnel

While Configuring GRE tunnel you may have specify source and destination address. That Source and destination IP are 1.1.1.10 and 2.2.2.10. These IPs will be routed in the internet and helps to bring ...
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2 votes

Packet flow in GRE Tunnel

In the outer IP header, it would definitely be 1.1.1.10 / 2.2.2.10, as this is what is used to route the packet to the tunnel endpoint. Note that you may not even need IP addresses on the tunnel ...
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2 votes
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Can different networks connected by MPLS run the same OSPF area?

You can certainly run OSPF on GRE interfaces and routers will exchange routes quite happily via the GRE tunnel. A GRE interface should be just like any other interface to OSPF, so normal rules would ...
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  • 2,476
2 votes

Qos implementation

Unless you have a specific agreement with your ISP and the whole path is under the control of you and your ISP, no there's no QoS on the Internet. All Internet router will simply ignore all QoS ...
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2 votes
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How to use ACL to deny sending packages to the GRE tunnel?

On R0 you need to deny ip 172.16.0.0/24 172.17.0.0/24 for the appropriate port/VLAN and vice versa on R1 deny ip 172.17.0.0/24 172.16.0.0/24 Make sure you put a 9999 permit ip any any (or ...
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2 votes
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Two channels between two switches

Depending on your actual goal, there are several possibilities. Load balancing your flows 'at will' requires them to be split across different VLANs or very delicate fine tuning. VLANs with spanning ...
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