Can I connect server to CX-4 on back of D-Link DGS-3420 switch?

Discussion in 'Networking' started by AveryFreeman, Jul 2, 2018.

  1. AveryFreeman

    AveryFreeman ESXi + ( BSD / ZFS ) = HAPPY

    Joined:
    Mar 17, 2017
    Messages:
    104
    Likes Received:
    9
    Hi,

    I was just wondering if it's possible to connect a server directly to the back of a DGS-3420 switch, it has two CX-4 connectors on the back that I know can be used for stacking switches together, but I wasn't sure if it could also be used for server connectivity.

    If anyone has any experience with these switches and doing this sort of thing I'd appreciate their feedback. I have absolutely 0% experience with any 10G+ networks.

    Thanks!
     
    #1
  2. Zuhkov

    Zuhkov New Member

    Joined:
    Dec 30, 2012
    Messages:
    27
    Likes Received:
    1
    Not familiar with that particular switch, but I did exactly this with an LB4 switch that has 4 CX-4 ports. Used Myricom 10G cards and DACs to connect them to the switch. Eventually moved to a newer switch with SFP+ due to the noise, but it worked quite well for several years. Critical question is whether the DGS-3420 supports the use of those ports for that purpose.

    Edit: if this describes the module you have, it would appear the answer is yes, you can connect servers to the switch via these ports: ftp://ftp.dlinkla.com/pub/DEM-420CX/DATASHEET-DEM-410420CX_02.pdf
     
    #2
    Last edited: Jul 2, 2018
  3. fohdeesha

    fohdeesha Kaini Industries

    Joined:
    Nov 20, 2016
    Messages:
    843
    Likes Received:
    623
    #3
  4. AveryFreeman

    AveryFreeman ESXi + ( BSD / ZFS ) = HAPPY

    Joined:
    Mar 17, 2017
    Messages:
    104
    Likes Received:
    9

    Hmmm... cool. But then, I want to go from Firewall/Gateway w/ Chelsio S310E-CXA --->> DGS-3427 10GbE Uplink #1 --->> DGS-3427 10GbE Uplink #2 --->> CX-4 to SFP+ cable --->> ProSafe XS708E 10GbE SFP+ Uplink --->> 10GBase-T Clients

    Does that setup make sense?
     
    #4
  5. fohdeesha

    fohdeesha Kaini Industries

    Joined:
    Nov 20, 2016
    Messages:
    843
    Likes Received:
    623
    If you can find a cx4 to SFP+ cable for not a bajillion dollars, sure. They tend to be a little costly though as they're "specialty items" in my experience
     
    #5
  6. AveryFreeman

    AveryFreeman ESXi + ( BSD / ZFS ) = HAPPY

    Joined:
    Mar 17, 2017
    Messages:
    104
    Likes Received:
    9
    I found one for $50 here:

    CX4 with Ejectors to SFP+ | DataStorageCables

    But I have no idea if it's electrically compatible. For all I know it just has the right ends.

    After seeing all these specialty 'media converter' devices that sell for hundreds of dollars, I'm experiencing a little PTSD.

    I'll email them and see what they say...

    The other option is CX-4 to 10Gbase-T (RJ45) ... but must chain using ASIC devices.

    The internets tell me my original idea of having a gateway server bridging both SFP+ and CX-4 would be slow AF.
     
    #6
  7. fohdeesha

    fohdeesha Kaini Industries

    Joined:
    Nov 20, 2016
    Messages:
    843
    Likes Received:
    623
    CX4 electrically is 4x serial lanes of 2.5gbps each, and SFP+ is electrically 1 serial lane @ 10gbps. They would need some type of SERDES chip in there I would imagine to serialize and de-serialize the 1 giant lane from the SFP+ connection into 4x separate serial streams

    but who knows I've been wrong before
     
    #7
    AveryFreeman likes this.
  8. AveryFreeman

    AveryFreeman ESXi + ( BSD / ZFS ) = HAPPY

    Joined:
    Mar 17, 2017
    Messages:
    104
    Likes Received:
    9
    That's very interesting, I had no idea. I've never worked with any 10GbE equipment before. Do you think going from 10GBase-T to CX-4 would be cheaper/easier?
     
    #8
  9. JustinClift

    JustinClift New Member

    Joined:
    Oct 5, 2014
    Messages:
    25
    Likes Received:
    11
    Hmmm, maybe just get a cheapo 10GbE card that has CX4 connectors and use a straight through CX4 to CX4 cable?

    I used to connect my old Mellanox MHGH28-XTC (ConnectX series 1) cards directly to the back of my HP Procurve 3400 switches, which have 2 CX4 ports on the back. Worked fine for years. :)

    Those cards are old, but can still be found really cheaply on Ebay so maybe worth experimenting?
     
    #9
  10. AveryFreeman

    AveryFreeman ESXi + ( BSD / ZFS ) = HAPPY

    Joined:
    Mar 17, 2017
    Messages:
    104
    Likes Received:
    9
    Yeah, you know, I got a CX-4 card, which I guess I could use in a machine that also has a SPF+ or RJ45 connector for my 10Gbe switch, I was thinking about using a software bridge but then I read that pfSense/FreeBSD is notoriously awful for doing that.

    I actually got a Chelsio T520-CR (SFP+) and a couple Intel X540-T2s (RJ45) and before buying all that stuff bought an old Chelsio N320e-CX before deciding I didn't want to mess with the CX-4 stuff. But I could just try another firewall distro, if I understood what I read the Linux kernel is OK at doing bridging (Linux bridge is highly developed due to its use in the VM space).

    The only problem is, I was demo-ing different firewall distros on my ESXi edge box and with my internet connection pfSense VM was consistently getting 680+ Mbps downloads on a close mirror using speedtest-cli. However, when I tried IPFire it would only get 450-500 Mbps. Not sure what that is about...

    hmmm... anybody know why there would be such a discrepancy? I'd hate to trade off decent 10Gbe lan speeds for shittier download speeds...

    Lastly, the saddest part about everything is I've only been able to get 4GBps in iperf3 max from server to server over my XS708e. It's a pretty crappy switch but I don't think that's the problem. Might be CPU-bound, only running E3-1230 v2s using ESXi with only 4 vCPUs and 16GB ram. Also might be the fault of pfSense being the software router though... just not sure, not enough experience with 10Gbe yet.

    Any tips, I'm all ears!
     
    #10
  11. JustinClift

    JustinClift New Member

    Joined:
    Oct 5, 2014
    Messages:
    25
    Likes Received:
    11
    Sorry, I've not used pfSense before, so can't really help there.

    With the transfer speeds... are you meaning 4 gigabits per second or 4 gigabytes per second? It's not clear from the context. ;)
     
    #11

Share This Page