Can an ME7350 gig uplink be config'd for 100mbps?

Unanswered Question
Sep 12th, 2008

We're purchasing a 100mb connection from our provider and they can had it off in either copper or fiber. They are actually handing us off a gig connection that they are provisioning at 100mb.

Is it best to connect that to one of the SFP uplinks and either:

1. connect it at 1000 speed, but change the bandwidth statement to 100,000? (this will be an L3 connection)

or

2. Connect it to an SFP uplink like and step the speed down to 100mb and use a GLC-T SFP.

Is guess the answer depends on whether the SFP ports allow for 100/1000 configured speeds.

I have this problem too.
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Mark Yeates Fri, 09/12/2008 - 13:24

Jim,

The GLC-T will support 100Mb/s. Option one is the only way to go if the connection is fiber and shape/police the bandwidth down to 100Mb. If you are able to have a copper link to your provider the GLC-T supports 10/100/1000 speeds so option number two will also work.

HTH,

Mark

Joseph W. Doherty Sat, 09/13/2008 - 03:48

For either a copper or fiber port that's gig, but a provider is provisioning only 100 Mbps, you'll likely need to either police or shape your traffic to 100 Mbps to avoid the provider from dropping traffic beyond the provisioned rate. Usually the need for either policing or shaping is eliminated if the physical port speed matches the provisioned rate. The latter also sometimes lends itself to "better" QoS configurations since not all platforms or IOS versions support complex QoS AQM (active queue management) in addition to enforcing a rate limiter or shaper.

The one advantage of keeping to a gig connection provisioned for 100 Mbps, short bursts will will go through at the gig rate.

andrew.butterworth Sat, 09/13/2008 - 04:13

On the Metro 3750 you have two Enhanced Services (ES) ports that have more functionality when used in a Metro environment than the standard ports - they support egress QoS service policies, MPLS, VLAN translation and some other stuff:

http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps5532/product_data_sheet0900aecd806e27b9.html

Unfortunately the ES ports can only operate at 1Gbps, so a GLC-T will work in these SFP slots, however you can't configure the speed. There are also two 'regular' SFP slots that will operate at 10/100/1000 but these don't have the additional features you get with the ES ports.

I looked into this a while ago and hit this limitation with the ME3750. I then came across the ME3400 which offers enhanced services on all interfaces (when running the Metro IP Access IOS image).

HTH

Andy

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