A 14-day free trial of SolarWinds NTM is available to get you started. This advanced and scalable network diagram tool offers an impressive range of features, giving businesses access to everything they might need to create comprehensive and automated network diagrams. SolarWinds ® Network Topology Mapper (NTM) ranks highest on our list of the best network diagramming software because it provides detailed network diagram capabilities in a user-friendly interface. This guide explains what a network diagram is and how network diagram software can help your business improve efficiency, in addition to recommending the best software for network diagrams available today. The reason why I came to this conclusion is because I looked at another service which is working on ADSL and the Dialer 1 interface is spoofed as up and the Virtual Access port it is bound to is up.Įither way, this leads me to another question.Network diagram software plays a crucial role in helping businesses understand their network and how their network components interact. Would I be correct in saying that the Dialer interface is always spoofed but the interface to which it is bound to is not? I am reluctant to paste the config in here due to confidentiality.ĮDIT: I think I see what is happening here. I have started a new job and am currently learning the network so that I can take over in a few months). (As you can probably tell I did not put this config together. How come Dialer 2 is still spoofing if that is the interface currently being use? Or perhaps Aysnc1 is the one being used? I have a site where the ADSL is currently down (Dialer 1) and the backup ISDN is up (Dialer 2), however, the output is as follows:ĭialer1 is up (spoofing), line protocol is up (spoofing)ĭialer2 is up, line protocol is up (spoofing) And so dial backup works because the BRI is spoofing. It remains in the routing table even though there is really no layer 2 connection. It acts like it is up even when it is logically down. And therefore the BRI would not function for dial backup because the IOS does not think that it can reach anything through the BRI because it is not in the routing table. If there is no call active on the BRI then there is no layer 2 (data link layer) connectivity and the interface would normally be down and therefore the subnet would be removed from the routing table. If we understand that basic operation then we can better understand the spoofing of the BRI. In IOS when an interface goes down, then IOS removes the subnet of that interface from the routing table and does not use that interface to get anything in that subnet. Lets start from a basic operation in IOS: if an interface is up then IOS puts the subnet of that interface into the routing table as a connected subnet and IOS now knows that it can get to anything within that subnet by going through that interface. Your understanding is pretty close to exact. My thought is that perhaps it would think that the connection is broken therefore unusable which in turn would ruin the idea of using it as a dial backup. My question is, why does the layer 2 protocol need to be 'fooled' in the first place? What would be the problem if the layer 2 protocol knew that the line protocol was down? When you establish the connection, the 'spoofing' should go away because a real layer 2 peer will now be available to keep the protocol 'up.'" Here, "spoofing" infers that they layer 2 protocol is being 'fooled' internally to think that there is a connection to a peer when in fact there is no connection, because there hasn't been any phone call placed yet. Normally, the absence of a layer 2 peer would cause the protocol to go 'down.' "The layer 2 protocol does not have a peer to communicate with when there is no phone call / connection established. I found this information on another forum: Hi all, I am a little confused when it comes to BRI/PRI sppofing itself.
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