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10

To add to Ron's point - a hub (...or a number of hubs) basically models the behavior of the original Ethernet, which is to say basically a big piece of coaxial cable. If one station transmits, all the others receive. When a station wants to transmit, it waits for an opening. If multiple stations try to transmit at the same time then a collision occurs and ...


9

Are uplink ports simplex ? Hub interfaces are simply hub interfaces, there really are no uplink interfaces. Why is it not possible for the hubs to read from the uplink port and broadcast the frame to the remaining ports ? Hubs are stupid. They simply copy the signals received on any interface to all other interfaces. They do not read anything, and they ...


9

That switch uses (Q)SFP+ ports which are essentially PHYless. You need to either use matching PHY type transceivers on both the switch and the host ports (e.g. 10GBASE-SR or 40GBASE-SR4) or direct-attach cables that are compatible with both sides. The Mellanox NIC has QSFP28 ports that should support QSFP+ modules as well - check the documentation. Note ...


8

What really happens is that any one flow only uses one of the links. Different flows are assigned to different links based on a hashing algorithm, so, in aggregate, you get the full bandwidth of the combined links, but any one flow will only get the bandwidth of a single link. You don't want to spread a single flow across multiple links because that will ...


7

Yes you can uplink different brand of switches using SFP. The term stacking in this context means that several switches act as a single one. This is always a proprietary (and model dependent) feature, and can be done only with switches of the same brand (and not all of them). SFP doesn't work only with fiber: there SFP to copper converters, so you can ...


6

It's not that you cannot physically create a hierarchy of hubs. You can. And it will work to some extent (limited by timeouts once your network is too big). The thing to know is that such a configuration from a networking point of view is flat - it is not a hierarchy. Why is a hierarchy not a hierarchy? Because as mentioned before, hubs are stupid. The ...


5

Adding to Ron's excellent answer, with the vast majority of switches there are three different hashing algorithms: MAC address (L2), IP address (L3) and IP address plus port numbers (L4). The algorithm combines both source and destination addresses and mixes them together in its own special way (sometimes documented) to choose a somewhat random yet ...


4

An Ethernet network (without fancy extensions) MUST be a tree. You can put a sticker on one of those hubs saying "main hub" and call it the top of your hierachy if you want the protcol doesn't care. What you can't do is have a hub at a lower level of the hierachy connected to more than one hub at the next level up of the heiracy. Furthermore the ...


4

To calculate the number of links in a fully meshed topology of N devices, the formula is this: Full-mesh links = (N)*(N-1)/2 Substituting numbers... = 40*39/2 = 780 However, you'd only have one link to every switch if calculated thusly. If you assume 4 links per switch, it's technically 4*780, or 3120 uplinks.


3

Goal: To the greatest extent possible, I would like to provide 10-GbE line-rate performance between any pair of hosts in both rooms. In order to truly guarantee 10G, you'll need 10G dedicated bandwidth between the rooms for each host. 10 hosts on each side would require a 10*10 = 100G link. Aggregated links might not be enough as the flows are balanced ...


2

I think your terminology of "uplink port" might be a source of confusion. Connecting a pair of hubs together by a patch cable will fail, unless one or both of the hubs does auto MDI detection, also known as MDI-X for Crossover. Some hubs have a doubled-up port where two RJ45 jacks are present, with one wired "straight" and the next one ...


2

I came to know that we cannot create a hierarchy of hubs. My question is why so? That depends on the book's definition of "hierarchy". In CSMA/CD, no repeater has more "weight" than any other, so there's no hierarchy in terms of priority. However, you can (and should) arrange repeater hubs in a tree (multi-star) topology, so there's a ...


2

It all depends on your workloads. If you've got eight "light" users that work with some office documents, surf the 'net, send and receive a few emails, oversubscription is a non-issue. It might not even matter if the users are connected by gigabit or only 100 Mbit/s. You could even have 40 end nodes or more on a single gigabit uplink without any problem. ...


2

You can do this with 10base2, but I'm sure you're talking about equipment which is using twisted pair. The main problem is how to detect that Router A has failed. Many failure modes -- eg CPU overloads -- leave the NIC fully enabled, so you can't use anything like "link light". Many failure modes have continuous transmit, so you can't use the Tx light. ...


1

There is no industry standard. Common practice is to use either the first ports, or last ports. But it's a personal preference (or maybe company policy), one can use any port(s). (If the switch has dedicated "uplink" ports, one would normally use those.)


1

First, you can't do link aggregation unless the carrier is also doing it on their end. But you can load balance between all three 100 m connections. It's best if you can run a routing protocol with your carrier, so you know that each link is available. Your routers can certainly do that. IMO the dsl lines are not needed if you have 300 Mb spread over three ...


1

Different brands of switches can be connected by SFP modules via compatible cables. SFP can work through several kinds of cables, not limited to commonly-used fiber. There are also copper transceivers,like 1000BASE-T transceivers with RJ-45 which take Cat 5 as transmission medium.


1

Yeah, the SFP on most enterprise switches is MOST COMMONLY used for a high-speed fibre uplink. They're there for that purpose. Obviously, you need the module to make it happen. I assume by long haul you mean SM and not MM optical modules.


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