Uplink Ports vs Normal Ports

[marcinwojcik]

Hi All

Let's say we have two types of switches:

1. WS-C2960-24TC-L (Uplinks - 2 Dual Purpose) 24Gb ports + 2 dual purpose uplinks

2. WS-C2960-24-S (Uplinks - None) 24Gb ports

Edit: I've given a wrong models.

Questions:

1. Is there any major difference between the uplink and "normal" ports on these switches?

2. Are the ports called "uplink" because we can plug SFP and use fiber (this is how I understend Dual Purpose)?

3. What will be a difference if I use Cat cable and ports 23 and 24 (etherchannel) to connect 2 x 24-S 1st type and 2 x 24TC-L 2nd type?

4. Do you know a website link which shows more info that this one: http://www.cisco.com/en/US/products/ps6406/prod_models_comparison.html

Thanks.

Marcin.

[Ton V Engelen]

Hi, Marcin

1. in fact, any switchport can be either an uplink or an access link. Its just a matter how things are connected and configured.

2. A fiber link is used as an uplink in many cases, but a copper link can be used to do the same.

3. Not sure what you mean as i dont know the 2960 model switches you use. But i asume you can connect these with an etherchannel

4. i am not at all familiar with the 2960, so i dont know this one. .

[Richard Michael]

Hello Marcin,

There is no difference between the uplink ports and the normal ports in the lower end series, however it makes a difference as you climb up the ladder, The below link might interest you,

https://supportforums.cisco.com/message/3413719#3413719

Thanks,

Ricky Micky

*Pls rate useful posts

[Latchum Naidu · Accepted solution]

Hi,

An uplink is a connection from a device or smaller local network to a larger network.
Some Ethernet computer networking equipment contains an uplink port. These ports simplify connecting different types of Ethernet devices to each other, such as when linking a local home network to a modem and the Internet.

Hubs, switches and routers typically designate one Ethernet port as the uplink connection. This type of port may be labeled WAN or Internet instead of uplink, but all serve the same purpose.

And regular switch port (normal port) where will use to connect end usr pc's or servers and all.

But at the end as like said, all ports erver the same purpose only.

Please rate the helpfull posts.
Regards,
Naidu.

[marcinwojcik]

Hi Ricky

Thanks for the reply. You wrote "however it makes a difference as you climb up the ladder...". What difference? I read the post which you suggested but and saw your reply but...

Could you be more specific? Are uplink ports more efficient/powerful in the terms of througput?

Thanks.

Marcin.

[Jon Marshall]

Marcin

Using the 4500 switch as an example. The 4500 switch has a module -WSX4418-GB which provides 18 1000Base-X ports. The connection to the switch fabric on the 4500 for this module is 6Gbps. So you can see that is oversubscribed ie.

18 Gbps on the module but only 6Gbps connection to the switch fabric.

On this module 16 of the ports are oversubscribed ie. they have a 4:1 oversubscription. So for each set of 4 ports they share a 1Gbps connection to the switch fabric.  Each set of 4 ports is assigned to a port group. The other 2 ports are the uplink ports and these are wire speed ie. they each have a dedicated 1Gbps connection to the switch fabric.

So 16 (ports) divided by 4 (the subscription rate) = 4Gbps ie. the amount that these ports can use. Then add the 2Gbps for the uplink ports and this is how you get to the 6Gbps switch fabric connection for the entire module.

In the above case clearly it would make sense to use the uplink ports to connect to other switches as you would then get the full bandwidth. If you used one of the 16 ports to uplink to another switch and you wanted the full 1Gbps throughput then for that port group you could only use one of the 4 ports.

Oversubscription is one of the major considerations you need to factor in when looking at the higher end platforms such as the 4500 and the 6500 switches.

Jon

[marcinwojcik]

Hi Jon,

Thanks for the explanation!

Are lower end switches like 2960 or 3750 oversubscribed or we have to worry about only in the case of high end switches?

Thanks.

[Richard Michael]

Hello Marcin,

Here is an analogy that i can come up with,

Lets say that i have a 6500 Sup 720, if you select a uplink port it has a high speed fabric connected to it, if you have a SUP 32 then you have a maximum forwarding rate of  15mpps.

However if you select a uplink in the linecard like 4418 then you must careful in selecting uplink ports as the ports are 4:1 oversubscribed and interesting thing in 4418 linecard is first 2 ports are non blocking and 4:1 oversubscribed on the remaining ports so theoretical throughput becomes 250Mbit/sec per port.

So on a whole yes there is a difference if you select a uplink in the supervisors on the

higher end models and Depends on the LC architechture you can chose which ports needs to be the

uplink.

Thanks,

Ricky Micky

*Rate if this helps

[Jon Marshall]

Ricky

and 4:1 oversubscribed on the remaining ports so theoretical throughput becomes 250Mbit/sec per port.

Just to clarify for the OP. The above statement is only true if all 4 ports in the port group are being used. If you only used 2 ports in that group then theoretical throughput becomes 500Mbit/sec. So it's a bit misleading to say the above without specifying how may ports in the port group are in use.

Jon

[Richard Michael]

Hi Jon,

Yes you are right, thats a sample calculation when all the ports in the port group are being used , you got the calculations

right

May be this looks better "4418 is non blocking on first 2 ports, and oversubscribed 4:1 on the remaining ports 3-18".

Thanks,

Ricky Micky

[jrasmussen1]

Hi all,

So I understand this discussion the switch fabrik support uplinks with full performance, other port have to share the capacity of the switch fabrik. So I think the following configuration should work (8 ports and 32 GBps switch fabrik) with full performance?

Computerraum Switch

Cisco Catalyst 2960G-8TC-L 8x 10/100/1000 Mbit Rackmount Switch

32 Gbps switching fabric (Catalyst 2960G-8TC, Catalyst 2960G-24TC, Catalyst 2960G-48TC)

  Forwarding rate based on 64-byte packets:

  Catalyst 2960G-8TC: 11.9 Mpps

configuration:

port1: other  Switches in the  Computerroom

port2: 1G  - 1. Server

port3: 1G - 2. Server

port4: 1G uplink - another switch

port5: 1G uplink - another switch

port6: 1G uplink to another switch

port7: 1G uplink to another switch
port8: 1G uplink to another switch

Thanks

[Joseph W. Doherty]

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Posting

Features of "uplink" ports vary per switch.  Sometimes they are not any different from "ordinary" ports, sometimes they offer additional features.  Such additional features might include: supporting MDI or MDI-X, more bandwidth (not just port bandwidth, might also include fabric bandwidth and/or ASIC allocation), additional media options (e.g. fiber), additional QoS features (e.g. ME3750's enhanced uplink ports), additional hardware buffering resources, etc.

Unfortunately, if there are differences, they are not always well documented.

2. Are the ports called "uplink" because we can plug SFP and use fiber (this is how I understend Dual Purpose)?

They are called "uplink" because that link is used to connected to the next "higher" device in the topology, e.g. edge switches that connect "up" to distribution layer devices.  Conversely, the "higher" layer's port to a "lower" level device, in the topology, might be called a downlink.  Because of distance, and other reasons, such links are offer fiber links but they're not always such.

"Dual Purpose" often is in reference to supporting copper and fiber, often with two physical ports, but only one of which might be active.  (In the config, either will be "seen" as the same logical port.

[krawietzj]

While I dislike bumping old threads, I'd rather add a related question to one so that related information is easier to find in one spot vs reading twenty different threads looking for an answer. With that said, on to my question.

I was searching for information on IE3000 switches in reference to the DPP Uplink ports vs the "normal ports". The datasheet says the switch has "Wire Speed Switching" but makes no reference that I can find about ports being oversubscribed. 

I am a bit inexperienced with backplane and switching fabric terminology so the information may be there and I'm simply overlooking it. 

Edit: I believe I found the answer, the normal ports are 4:1 oversubscribed if I read the other datasheet correctly. 

Thanks,

JK

[scottspa74]

Hi, I recently got my hands on a WS 3850 switch that has none of the uplink ports.  It was free and really is for tinkering.  I don't recall from my cisco training in school what the uplink ports are used for.  From what I'm reading, it looks like if I wanted to implement this switch in my home network, uplink ports are what I'd want to use to link it to my router, is that correct?  (my home router is just a loaner from the ISP, but it handles DHCP, NAT, etc).  The 3850 is a layer 3 switch, but would that cause a mess to plug a L3 switch into an actual (wireless) cheap router?  I've come up with a VLSM scheme that would work for my home topology?  The network modules appear to be pricey, and I'm trying to sort out if I could just use any of the standard 24 ports to plug into my router and share the internet access to the desired vlans I create on the switch.   (I took the entire cisco 200-301 content at community college as part of a digital forensics degree, but didn't get my CCNA right away, and my cisco classes were over a year ago now, and I'm just forgetting so much - even though the networking aspect was my absolute favorite part of the degree/course - in school it's hard to find time to drill down to be expert at any one thing, always being pushed along to the next set of classes). 

Thanks for any responses. Sorry to resurrect such an old thread. 

[Joseph W. Doherty]

The Catalyst 3850?  If so, it's "documented" "uplink" port(s) could "require" a separate interface module.  Which as you noted, is pricey.  Further, for your usage case, and topology, very, very unlikely you would need the advantages of such a module's port(s).  I.e. often, logically, any switch port can serve as an "uplink" port.

As noted in my long ago prior post, ports used for uplink purposes might have additional hardware resources supporting them, often increased buffer space, and/or possibly less contention for fabric and/or ASIC capacity.  They might also offer options not available on the "normal" edge ports, such as fiber and/or higher bandwidth per port.  (BTW, years ago, it was often common to find smaller switch "uplink" Ethernet ports, with their tx and rx pins reversed from the other "edge" ports.  This so you could use the same "straight-thru" Ethernet cable used for edge hosts and between switches.)

As to adding a 3850 messing up your home network, it could, if you try to use its L3 routing features beyond just those supported by it as a "dumb" L2 switch.

For example, yes you can route on your 3850, but likely the ISP loaner "router" wouldn't work with your 3850 doing routing.  I.e. creating VLANs "behind" the 3850, which you wish to used on the Internet too, might not be possible unless he 3850 supports NAT or PAT (which I don't recall that it does).