4500-X and port speed mix

[adcampos]

Hi Guys,

I need some help understanding the 4500-X architecture. I know this switch is oversubsribed less than 20:1 using all ports as 10Gig.

Well, I'm designing a collapsed Campus using these 4500-X as CORE/Distribution. A key part is that some of the uplinks that will connect to the 4500-X are 1 gig and some others 10Gigs. Can I mix these two speeds in any way, like 6 ports being 10gigs and all the rest 1gig or half of the ports 1gig and all the rest 10gigs, or does it depends on the model? I'm selecting the 32x 10gig port.

Any help is appreciated.

Regards,

Adrian.

[Joseph W. Doherty]

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Posting

I suspect you might misunderstand the oversubscription ratios.  What's noted in, for example, the 4500-X white paper refers to using ports to and from other network devices.  For example, if you use 32 10g ports for downlinks and the optional 8 10g ports for uplinks, those uplinks are now oversubscribed 32:8 or 4:1.  Assuming you can use any port for any purpose, you could use 20 ports for downlinks and 20 ports for uplinks and not have any oversubscription.

The 4500-X is described as non-blocking, and with 800 Gbps fabric.  I.e. it can handle even the bandwidth demand of the maximum of all 40 10g ports.  However it's also described with 250 Mpps which isn't enough to guarantee wire-rate for all 40 10g ports (which would need about 600 Mpps).

The SFP+ supports 1g or 10g; don't see any restrictions noted.

[adcampos]

Let me see if I understood this correctly now.

According to the white paper:

" The Cisco Catalyst 4500-X Series Switch offers 800  Gbps of backplane bandwidth with up to 250 Mpps switching capacity that  provides up to 32 nonblocking 10 Gigabit Ethernet downlink ports and up  to 8 nonblocking 10 Gigabit Ethernet uplink ports using a pluggable  module".

So this means the 4500-X offers full b/w (line rate) on each port with no oversuscription, including the optional 8x10gig module, correct?

However in the "Managing Oversubscription" seccion says:

"The Cisco Catalyst 4500-X offers 32 x 10 Gigabit  Ethernet downlink ports and 8 x 10 Gigabit Ethernet uplink ports. With  the preceding oversubscription ratio, these 32 x 10 Gigabit Ethernet  downlink ports can aggregate up to 32 access-layer switches or ~6000 end  user devices on the access-to-distribution links with less than 20:1  oversubscription, and 8 x 10 Gigabit Ethernet uplink ports provide 4:1 oversubscription for distribution-to-core links"

According to your explanation the oversuscruption described here refers to the access switches and core devices not the 4500-X itself, correct? And you are not 100% sure about the "nonblocking" also as the number of pps seems low to you, right?

I also found no restriccions in the SFP+ ports. However, if for any reason the ports in the 4500-X are somewhat oversuscribed, restriccions will apply. And I would like to be 100% sure before ordering this device.

Anyone with access to one of this boxes, the 32x10gig port specifically, that can provide a "show platform chassis module 1" output? or similar to see the number ASIC on the 1 module

Thank you.

Adrian.

[Joseph W. Doherty · Accepted solution]

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

" The Cisco Catalyst 4500-X Series Switch offers 800  Gbps of backplane bandwidth with up to 250 Mpps switching capacity that  provides up to 32 nonblocking 10 Gigabit Ethernet downlink ports and up  to 8 nonblocking 10 Gigabit Ethernet uplink ports using a pluggable  module".
So this means the 4500-X offers full b/w (line rate) on each port with no oversuscription, including the optional 8x10gig module, correct?

That's my interpretation too, i.e.full b/w.

However in the "Managing Oversubscription" seccion says:
"The Cisco Catalyst 4500-X offers 32 x 10 Gigabit  Ethernet downlink ports and 8 x 10 Gigabit Ethernet uplink ports. With  the preceding oversubscription ratio, these 32 x 10 Gigabit Ethernet  downlink ports can aggregate up to 32 access-layer switches or ~6000 end  user devices on the access-to-distribution links with less than 20:1  oversubscription, and 8 x 10 Gigabit Ethernet uplink ports provide 4:1 oversubscription for distribution-to-core links"
According to your explanation the oversuscruption described here refers to the access switches and core devices not the 4500-X itself, correct? And you are not 100% sure about the "nonblocking" also as the number of pps seems low to you, right?

re: oversubscription, yes not the 4500-X itself.  Look at figure 7 in http://www.cisco.com/en/US/prod/collateral/switches/ps10902/ps12332/white_paper_c11-696802.html.  What it shows in oversubscription as from downlinks to uplinks, i.e. more of the former than the latter.

"Nonblocking" wouldn't be relevant to the PPS, that just means the traffic shouldn't need to wait (block) for access to the fabric.  The 250 Mpps, though, doesn't guarantee line-rate for small packets.