UPLINK Bandwidth Calculations

[Muhammad Kamran Shahzad]

Dear Experts,

Can you please advise about below query.
I have many Cisco switches in my network.

This question I am raising only for referring to 1 Cisco switch and I hope same strategy should be for all cisco switches.

WS-C2960S-24TS-S

I have 26 Gigabit ports from Gi0/1-26 Where Gi 0/25-26 are other side (Considered as Uplink)

I have connected 2 Uplinks in Gi0/25 and Gi0/26.

Advise if Cisco switch can give throughput of 2Gig or it will be bound to 1Gig only ?

# Question Number 2

Let say if it will give throughput of 2Gig and if we connect another uplink to Gi0/24 so will throughput will be 3 Gig or not ?

I just want to understand so if it will not be 3Gig then it's mean we have to use only Uplink ports for Upstream connectivity ?

How we can check maximum throughput capacity of the Switch before in production, like in specifications what it should be called.

This will help me alot to solve my confusion as currently I have connected 2 Uplinks in Gi0/25 and Gi0/26 and throughput not crossing 1Gbps and getting complaints as well.

Both links are coming from same upstream and i have distributed the load using PVST.

below is more detail.

Service From Upstream from Vlan 321 to 340

Below is current config 


interface GigabitEthernet0/25
switchport mode trunk
storm-control broadcast level 20.00
storm-control multicast level 20.00
storm-control action trap
spanning-tree vlan 328 cost 20000


interface GigabitEthernet0/26
switchport mode trunk
storm-control broadcast level 20.00
storm-control multicast level 20.00
storm-control action trap
spanning-tree vlan 321-327,329-330 cost 20000

so as per above config I am running only vlan 328 on Gi0/26 interface 


Thanks

[Joseph W. Doherty]

With your config, you have L2 link redundancy, and any VLAN would be limited to link's bandwidth, 1g.

The usual "better" Cisco solution would be to create an Etherchannel using multiple links.  This would provide, in theory (with ideal load balancing), the aggregate bandwidth of all the links to all your traffic, but any one flow would still be limited to using just one link.  For a dual link Etherchannel, although you will have 2x the aggregate bandwidth, in practice, you'll usually only obtain about 50% more effective bandwidth.

Lastly, yes you can often use other ports for uplinks.  The "gotcha" is, often switch  hardware provides "uplink" ports with more resources as often such ports are expected to usually have more traffic.  Believe that's true for any 2960 switch.

[Muhammad Kamran Shahzad]

Yes This is Layer 2 traffic going towards pppoe server
Actually there is also a challenge to create port channel as both links are comming from different locations and not coming from same upstream switch.

Traffic from both links going towards same PPPoE Server.

so it's mean even we create ether channel then throughput will not be more then 1Gbps ?

I want to achieve more then 1Gbps bandwidth so if I replace switch to 10G switch then also my uplinks will be still 1Gbps as uplinks are wireless links.

please advise the best practice as my main aim to achieve bandwidth throughput more then 1Gbps which is currently capped at 1Gbps.
Thanks

[Joseph W. Doherty]

You do have some options, some of which may require L3.  Also some options may only be available 3rd party.

Options such as dynamic load balancing by flow (e.g. PfR), equal load balancing by frame/packet/fragment (e.g. MLPPP, IMUX, CEF), and/or compression (e.g. WAAS, WAFS).

Since your primary bottleneck appears to be wireless, possibly that too might be upgraded (WI-FI6 or later?).

[liviu.gheorghe]

What @Joseph W. Doherty was explaining is that if you configure a Etherchannel bundle of 2 GigabitEthernet links, you will definitely have more throughput on the Etherchannel than 1 Gbps, but you will not achieve 2 Gbps. Real life scenarios you will attain a throughput of 1.5 Gbps, possible more, possible less depending of a number of factors that dictate how the switch distributes traffic of the Etherchannel on the individual bundle links.