2 Uplink Ports

[Alfie Overacre]

Ihave an old Linksys switch (EZXS55W) and it has worked fine for many years now, but I tried to hook something up today to the last open port and noticed the device didn't work when I did this. When I looked about my switch, it says that it disables that port when using the Uplink port.

I'm still a bit fuzzy on what the Uplink port does for me, I had always assumed that this Uplink port was for me to plug into from my router which is elsewhere in the house and hooked up to the modem so it could allow the switch to work for my other devices. I guess I need more than 5 ports now, but I see newer switches do not have this Uplink port generally anymore. Can I safely buy a new 8 port switch that does not have an Uplink port and maintain the exact same functionality?

If I understand what I'm reading correctly, newer switches did away with the need for a dedicated Uplink port so now the switches intelligently do whatever the Uplink did? I don't want to get further off from the accurate answer to this, so I just want to understand the technicality behind this so I'm not uninformed.

The one thing I guess I'm seeing from this though, if a switch is say an 8 port switch that means 1 port will be used to feed from the actual internet connection (whichever cable is providing it to the switch) and then the other 7 can be devices that need access to that shared network connection and by that virtue, the internet. It does not however, work like 5 port means it has 6 physical ports with one being the "internet" connection, and the other 5 being devices that need to be hooked up, correct? The latter is how I always thought it worked, but thinking this is incorrect now.

They are used to connect together 2 switches with a standard straight-trough cable.(otherwise it would require a cross cable where the transmit and receive are crossed in the cable rather than on the switch port)

Some switches came with 2 physical ports that were actually the same logical port , the first one being wired normally and the second wired "crossed". So you were able to use only one of the physical port a a time, depending if you connect a PC (or a router) or a switch.

Nowadays this generally doesn't matter anymore since most interfaces are "auto-mdix", meaning that the interface detect the type of device connected and cross transmit and receive internally if needed.

Note: this apply mostly to 10Base-T / 100Base-TX ports, since Auto MDI-X is nearly ubiquitous on gigabit Ethernet, and doesn't apply to 10GB Ethernet and above where there's no more dedicated transmit / receive wires.

This has to do with how (UTP) Ethernet cabling works. In the old days, end point devices (like your PC) would use wires 1 and 2 to transmit data, and wires 3 and 6 to listen ( :Ethernet_MDI_crossover.svg) (*). The switch on the other side of the cable would listen on wires 1 and 2, and transmit on 3 and 6. Now if you would connect two siwtches, this would not work with a regular cable, because both switches would use the same wires in the cable to transmit. On solution for this is to use a special crossover cable, within which the cabling is crossed. Another solution is to have a specific "Uplink" port on the switch, which is wired as an end-point and uses the same wires to listen/transmit as a regular PC for instance.

With modern devices this is all a moot point, since practically every device uses "Auto-MDI-X" ( -dependent_interface#Auto_MDI-X) to sense which wire to listen and to transmit on. This standard was introduced in 1998, so it's very rare to find use for your old crossover cables today.

As for your Linksys switch: you can use the Uplink port to connect an end-point if you would use a crossover cable. However, in the internal wiring in the switch the Uplink port is the same port as port number 5 ( -article?articleNum=132646), so you can only use one of them (either the Uplink port, or port 5, not both simultaneously).

However, we currently have two wiring closets with EX4200s connected over fiber with one SFP port per switch. Have I misunderstood and sending sending regular traffic through a VCP port is supported and how could I configure the ports to support it?

An uplink port can be used for regular traffic or it can be configured specifically as a VC port. When this is done it will be used to traffic flows between the switch chassis and can't be used for uplink purposes without removing the VC configuration statement.

We have 2 closets with 5 EX4200 switches. (3 in one and 2 in the other). Switches in the same closet are connected with their dedicated VC ports. One switch in each closet has an uplink module which connects them for regular traffic and they are all on the same virtual chassis.

Specific to my situation, we are adding 3 new EX4200s in different wiring closets that will have a home run back to the closet with the three switches, and be on the same VC. I would like to have a single run back, like what I'm currently set up for in my other closet.

If you want all the switches you have deployed (across all closets) to appear as a single virtual chassis (with 8 members) then you will need to configure the uplink ports between each closet and the "central" one (with 3 switches) as VCe (Virtual Chassis Expansion) Ports.

If you have redundant fibres between each closet and the central one, I would also configure link-aggregates between your edge closets and the central one, ensuring that the primary and redundant are on separate physical switches in the "core".

I appreciate the clarification.

Reading back, Kevin said "When this is done it will be used to traffic flows between the switch chassis and can't be used for uplink purposes". I'm thinking I may have made a mistake in terminology and had confusion in the function of a VC port, when I said I wanted this to be an uplink, (I was considering the connection back to the core was an "uplink", even though they were part of the same virtual chassis).

The traffic will only be flowing within the VC and will not need to uplink to anything external. In this case, I would configure the uplink ports as VCP, not worrying about anything acting as an uplink, and consider adding a second for redundancy.

For the purposes of traffic flow, a VC Port and a normal Ethernet uplink would essentially do the same thing (forward traffic to upstream destinations) but the a VC port will also send VCCP traffic to coordinate chassis topology and functionality to other VC members.

An uplink port does recognize vlan traffic and may be used in redirecting traffic based on the vlan. This typically is called the trunk port and have limited vlan support or all vlans, pending on the config. Thatlevel 2.

Alex is actually correct. And this is part of the problem. There is no -standardized- definition of the terms being used.

Company One says A is trunk port, B is uplink.

Company Two says B is trunk, there is no uplink

Company Three says X is trunk, B is uplink.

Ps By the way linking 2 x 1930 via the sfp+ port between them (used a Ubiquiti DAC) seemed to work but I think more configuration is needed like

-do I set jumbo frames on? 9000MTU instead of the 1500 default one? Is there a change of continues loop problems this way? Meaning do I have to set up STP?

-Today I tried connecting a server via a 10Gbe DAC cable to one of the 4 sfp+ ports. It seemed to work meaning that the server could have

net but don t have a way to check the 10g connection. Still this port too doesn t need configuration to see it as a 10g meaning MTU value again and any other possible option needed.

------------------------------

Jim tsoutsouras

------------------------------

Original Message Original Message:

Sent: 12-13-2021 03:59 PM

From: Jessica Mitchell

Subject: 1930 uplink ports usage info

Hi Jim,

I'm partnering with my internal teams about your questions. I'll respond back to this thread once I have more information. Thank you for your patience.

------------------------------

Aruba Instant On Communications

Original Message:

Sent: 12-09-2021 07:01 AM

From: Jim tsoutsouras

Subject: 1930 uplink ports usage info

Hi

After reading and watching a couple of links about uplink ports (a nice one uplink ports definition but still cant figure it out), I d like to ask about a more techy insight for a probably simple configuration of mine that I need to setup.

I need to connect 2 Aruba switches together and by together term I mean ..... right now I am almost full at the first switch and I d like to expand it by connecting another Aruba 1930 in order to be able to connect to the network more than the current 48 clients.

1a.Is this done by connecting via a DAC cable one of the four 10gbe uplink ports of the current switch to the other one?

1b.If yes do I need to enable jumbo frames for the specific port on both switches?

1c.Do I need some extra configuration inside the gui? I ve searched and didn t come up with anything.

Probably I can connect the uplink port of the one switch to a regular port of the second but that would demand for a special sfp+ -> rj45 cable and dont feel like doing it this way (if that was a possibility all along)

2.Are the4 sfp+ ports dual purpose ones? Still didnt find in gui anything like a software switch to allow to function as a regular or uplink port

3.Can all uplink ports used independently (because there is a line that seems to connect the lower left - right 10gbe ports and thought that this means you can use one of them each time)

4.I need to connect 2 servers between them (not by connecting them via their 10gbe network card) via the switch. There is need though, to be used the fast lane (10gbe)

Since these 4 ports are uplink ports, can I use them and connect each server with a 10gb3 copper cable and afterwards they can see each other and also have internet access?

5.In case I had an extra third 10gbe switch, then I could connect the 2 servers via their 10gbe network path to the switch. After that step, how that switch is supposed to to be connected with the Aruba switch (I mean which port) in order for both servers to have net access?

Thank you in advance.

------------------------------

Jim tsoutsouras

------------------------------

3a8082e126