Do switches that provide 2 SFP+ 10GB uplink also allow downlink?

Discussion in 'Networking' started by jang430, Mar 4, 2019.

  1. jang430

    jang430 Member

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    Cisco Catalyst 4948 Switch

    I want to buy a switch that allows me to connect my Synology DS1618+ and my Dell T630 server via Intel X520-DA2 10Gb nic.

    The abovementioned switch says it allows the 2 sfp+ to provide 2 10Gb uplink, so my understanding is, when my Synology is connected to that port, and Dell T630 also connected on the other port, all the workstations connected to the other 48 ports can experience faster performance when they access files from those 2 devices all at the same time. 10GB / 48 ports, rather than 1 GB / 48 ports. My question is, if both Synology and Dell T630 are connected to the switch, does the Dell T630 get to access the Synology at 10 Gb?
     
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  2. Blinky 42

    Blinky 42 Active Member

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    In general yes, you should have 10G connectivity between the "uplink" ports as well as being able to use 10G aggregate from any mix of 1G and 10G ports on the switch.

    Some early 1G + 10G switches would have multiple 10G ports but not be able to handle line rate on all of the 10G ports at the same time. Searching for reviews of the switch in question from when they were released will often go into details about what configurations can handle line rate, what the topology of the switch ASIC(s) are inside etc.
     
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  3. jang430

    jang430 Member

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    Looking at the model only shows uplink of 10GB, and no mention of downlink anywhere. More important to me is a 10GB connection between T630 and Synology NAS. I hope we can confirm this.
     
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  4. mstone

    mstone Active Member

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    I don't understand what you're asking. Do you think they implemented a unidirectional 10Gbps link?
     
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  5. i386

    i386 Well-Known Member

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    Nope, the hosts are still only 1gbe. But your synology can serve more hosts simultaneously :D
    Yes.
     
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  6. Stereodude

    Stereodude Active Member

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    He just needs to make sure he gets a directional Ethernet cable and installs it the right way.
     
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  7. jang430

    jang430 Member

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    I bought 10Gtek 10G SFP+ DAC Cable 2m - Cisco SFP-H10GB-CU2M Twinax Copper Passive Cable for my NIC to be installed to Synology, Dell T630, and the switch mentioned above.

    Thanks guys for the clarification.
     
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  8. Terry Kennedy

    Terry Kennedy Well-Known Member

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    Be VERY careful here. The 4948 has 4 SFP (not SFP+) ports shared with the last 4 copper ports. The 4948-10GE has 2 dedicated X2 slots for 10GbE optics, but they are not SFP+. And the 4948-10GE is one of the Cisco models very prone to the "reboot of death" - they claim it was a memory vendor that supplied sub-standard chips, but the truth is that of the 5 memory chips, 3 are on the top of the module and get good airflow, and 2 are on the bottom and get absolutely no airflow. Gory details here. Note that that post is from well over 4 years ago and I no longer fix them, I just recycle them and buy 4948E's on eBay [advertising link, not mine] (well under $200 with dual power supplies if you're relatively patient).

    The 4948E switch (and the 4948E-F, which is the same unit but with reversed airflow) has 4 10GbE SFP+ slots, not shared with the 48 copper 10/100/1000 ports. But a lot of eBay [advertising link, not mine] sellers either don't know what they're selling or are intentionally mis-representing the product. A 4848-E (technically WS-C4948-E) is a plain old 4 SFP switch with an Enterprise software license. A 4948E (no dash) is the one with 4 SFP+ ports. All of the undesirable 4948s are Cisco blue-green, while the desirable ones are silver. Note that all of these are well past End-of-Life from Cisco.
     
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    Last edited: Mar 4, 2019
  9. jang430

    jang430 Member

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    @Terry Kennedy Oh man, thanks for these info :) . Too much information for me to absorb hahaha. I originally am looking at Cisco WS-C4948E-S Catalyst 48-Port Gigabit 4x SFP+ 10GB Switch w/ AC Power 658759114921 | eBay . Can you help me confirm whether this is one of the desirables? I will get reboot from this model? Noted on the EOL, expected it to be so hance the price.

    "The 4948E switch (and the 4948E-F, which is the same unit but with reversed airflow) has 4 10GbE SFP+ slots, not shared with the 48 copper 10/100/1000 ports." When you say not shared with 48 copper, meaning, no access from 48 to 4, and from 4 to 48?

    I intend to buy the Cisco on the link above, and use 10Gtek 10G SFP+ DAC Cable 2m - Cisco SFP-H10GB-CU2M Twinax Copper Passive Cable | eBay with Intel X520-DA2 10Gb 10Gbe 10 Gigabit Network Adapter NIC Dual E10G42BTDA | eBay

    Can you help validate?
     
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  10. Terry Kennedy

    Terry Kennedy Well-Known Member

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    Yes, that's one of the good ones and from a seller I've done business with. It does only have a single power supply (it only needs the one unless you want redundancy).
    No, they're all on the same switch fabric. On the original 4948, you had to say either "media-type sfp" or "media-type rj45" because it was only a 48-port switch, even though it had 52 physical connectors. The 4948E is a 52-port switch, so you can use all 48 copper ports and the 4 SFP+ ports at the same time.
    Passive DAC cables should work fine - there are no "magic footprints" in them like there are in optics to make you buy genuine branded optics.
     
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  11. jang430

    jang430 Member

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    Last question, I will connect my Dell T630 and my Synology DS1618+ using Intel X520-DA2 10Gb 10Gbe 10 Gigabit Network Adapter NIC Dual E10G42BTDA | eBay to this Cisco switch. Will the Dell T630 server be able to access the Synology NAS at 10Gb speeds? I believe this switch says 10Gb uplink, I understand that it has this 10Gb pipe sharing to all 48 ports. But does it share the 10Gb to the other SFP+ ports?
     
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  12. Terry Kennedy

    Terry Kennedy Well-Known Member

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    As long as the T630 and the Synology both have 10GbE ports, you should not run into any network limitations. You probably won't get 10GbE "wire speed" out of the disks in the Synology (that would be 1250Mbye/sec and with 6 disks striped running flat out, you'd be hard-pressed to get that speed).
     
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  13. jang430

    jang430 Member

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    Thanks @Terry Kennedy. You've been very helpful. Excited with my new purchases :)
     
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  14. Terry Kennedy

    Terry Kennedy Well-Known Member

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    The latest IOS software for it is version 15.2(4)E7 and the latest ROMMON (pretty much the BIOS) is 12.2(44r)SG11.
     
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    Evan and jang430 like this.
  15. Evan

    Evan Well-Known Member

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    Everything @Terry Kennedy just said in those posts about the 4948’s.

    In general in the enterprise line of Cisco switches all so called ‘uplinks’ can be either trunk or access ports no issues.
    Only on the low end enterprise and small business switches is there often some dedicated ‘stack ports’ and these usually have special cables anyway.

    Just be aware that some switches the last 4 or 6 fiber ports are sometimes locked in speed as a group. eg they are all lock at either 10G or 40G but you can’t run some ports at one speed and other ports at a different speed.
     
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  16. jang430

    jang430 Member

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