Gigabit Routers & Fast Ethernet Switches

[jdjefferson60372]

Hi,

I notice with many of Cisco's labs, that fast ethernet switches are used with gigabit routers. In reality, is this best practice? Would the lesser fast ethernet switches in these cases slow the traffic??? If not please explain why. If so, why would this be implemented?

Thanks,

joe.

[Richard Burts]

Joe

You begin your post by describing Cisco lab exercises, and then ask a question about "in reality". To state the obvious: a lab exercise is not reality. For lab exercises the Fast Ethernet switches are more simple, easier to configure, and certainly good enough for the purpose.

Your question about reality is a valid question, and there is not a simple yes or no answer. I would suggest that for many "real" production environments a FastEthernet switch as an access switch is cheaper, easier to provision/configure, and good enough (does not negatively impact network performance). There certainly are some production environments where you might need the higher performance (and higher cost) of a Gig Ethernet switch. So the answer is that reality is complex and you need to consider on a case by case basis whether a Gig switch is justified or a FastE switch is good enough.

[Joseph W. Doherty]

What specific "gigabit" routers?

Why I ask, many low-end to middle series Cisco routers come with gig Ethernet interfaces but do not have the performance to even support one full duplex gig flow.  So using those, with their gig Ethernet interfaces, actually running at FE, can make a lot of sense, both in a lab and real world.

[Martin L]

It depends on traffic patterns and network design. In the past, we had network designs for 80/20 traffic patterns where 80% of traffic stays locally (LAN) while 20% goes outside LAN. However, today's' networks traffic is more like 20/80 where most of traffic goes out of LAN like to Data Centers, the Cloud and Internet, etc.  So, what you see is traditional pattern where hosts on LAN will use fast Ethernet ports while uplink port (gig port on switch) is connected to gigabit router who is default gateway for LAN. So, Yes, in case of 20/80 pattern, fast Ethernet ports will slow the traffic down.

Today, if you buy new Cisco LAN switch, all "regular" ports are Gig ports and uplink ports are "flexible" (replaceable 2-, 4-port add-on fiber modules) with speed from 1 Gig to 10 Gig, or even 40 Gigs. see cat 9000s series switches.

Regards, ML
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