Distribution design w/ 3560s & 4500 Sup IV

[mo shea]

Hi...

We have  a building that is currently connected to our LAN via 1G fiber links. A 6500 sup 2 (PFC2, MSFC2, no SFM, no dCEF) distribution switch is currently present in this building, serving three floors, each floor having 2 2950 switches (connected via 1G uplinks to the 6500).

We have received a new 4500 w/sup IV and 4 3560E-48 PD switches froma cancelled project. I was going through the 3560 datasheets and found that these give 101.2 mpps forwarding and 128 gbps switch fabric. Now I was thinking of replacing the old 6500 (7 years, Cat OS) with the new 4500 w/sup IV and connecting the 3560's in place of the 2950 edge switches, but I am worried that it will be undermining the superior the forwarding power and bandwidth capacity of the 3560 switches (the 4506 w/ sup IV has 48 mpps and 64 Gbps).

Shall I go on with this design? Any suggestions?

All help is appreciated.

Mo Shea

[Giuseppe Larosa]

Hello Mo Shea,

what kind of linecards have you got on the C4500?

be aware that WS-4548 and older linecards have a limit of 6 Gbps to/from the backplane and that ports are served in groups of 8 ports by an ASIC and share 1 Gbps traffic in/out.

Only newer linecards with final E in name have 24 Gbps per slot but requires also the newer supervisors to be used.

So the performance problem of your C4500 is probably worse of what you are thinking of.

I would suggest you to build a stack of two C3560 as your distribution switch and to use the C4500 and the two other C3560 at access layer.

Access layer switches can be connected with a 2GE etherchannel connected to two ports one on core-1-1 and one on core-1-2 (this is permitted by switch stack).

You will need to get the stackwise cable for C3560.

Alternatively, you can use a single C3560 as your distribution and you can keep c6500 as second distribution switch

Hope to help

Giuseppe

[mo shea]

Thanks Giuseppe for your reply.

By the stackwise cable do you mean a normal fiber cross cable, because the 3560 doesnt support stackwise technology like the 3750?

As for the 4500, there is 1x WS-X4418-GB card (18 GBICS, port 1 and 2 run wirespeed, 3 - 18 4:1 oversubscribed), 1 x Sup IV, 2 x WS-X4424-GB-RJ45 (again 4:1 oversubscribed).

Comparing to the existing 6509 (Sup 2, no SFM), it seems that, at least from the spec sheet, the 4500 has better mpps and gbps values. One another question is if 3 3560s were connected to the 4500 via 1G uplinks, wont the throughput of the 4500 not be overwhelmed since the higher mpps and gbps value of the 3560 be limited by the 1g uplink going to the 4500?

I'm just a bit confused whether the throughput and backplane of the 3560 is locally significant to the switch or how exactly will it effect the inferior 4500?

Thanks again.

[Jon Marshall]

tacobell wrote:
Thanks Giuseppe for your reply.
By the stackwise cable do you mean a normal fiber cross cable, because the 3560 doesnt support stackwise technology like the 3750?
As for the 4500, there is 1x WS-X4418-GB card (18 GBICS, port 1 and 2 run wirespeed, 3 - 18 4:1 oversubscribed), 1 x Sup IV, 2 x WS-X4424-GB-RJ45 (again 4:1 oversubscribed).
Comparing to the existing 6509 (Sup 2, no SFM), it seems that, at least from the spec sheet, the 4500 has better mpps and gbps values. One another question is if 3 3560s were connected to the 4500 via 1G uplinks, wont the throughput of the 4500 not be overwhelmed since the higher mpps and gbps value of the 3560 be limited by the 1g uplink going to the 4500?
I'm just a bit confused whether the throughput and backplane of the 3560 is locally significant to the switch or how exactly will it effect the inferior 4500?
Thanks again.

You can only send so much through a 1Gbps uplink so the internal switch fabric of the 3560 does not have a direct effect on the 4500. Having said that the worry would be the oversubscribed WS-X4418-GB module in your 4500. If with ports 3 - 18 you only needed to connect in 4 connections then you could get around the oversusbcription but if you needed to use more then this is potentially a serious bottleneck.

It's also very important to identfy just how much traffic you want to switch from the 3560s to the 4500. It may or may not be a problem using the 4500 depending on how much you need eg. if each 3560 needed a 3Gbps etherchannel then you would definitely be oversubscribed on the WS-X4418-GB card.

Jon