bandwidth command on a Gig Ethernet Interface

[sidpatel3691]

Need clarification on the bandwidth command on an gig interface.  Currently I have a gig interface with speed set to 100, and it is WAN connection to ISP is 10 mbps.  BW is set to 10000 on this interface to match to ckt rate provided by ISP.  Now there are talks of upgrading it to 30 mbps ckt. 

I understand bw command plays its role as a metric when IGP protocols are used to determine best path to multiple destinations. However, this interface is a WAN ckt and not running any IGP or QOS.

So does the bw command on this interface have to be changed to 30000 when the ckt is upgraded to 30 mbps.

Bottom line, even though this is a gig interface with 100 mbps speed, the bw/transfer rate will be limited to 30 mbps only, correct ?

[Georg Pauwen]

Hello,

the bandwidth statement has no effect on the speed of the interface. It is, as you already stated, by OSPF and EIGRP for computing metrics. So, in your case, it is basically irrelevant....if your ISP limits your connection to 30Mbps, that is what you get, regardless of what 'bandwidth' value you use...

[Joseph W. Doherty]

To add to Leo's post, your interface will transmit as whatever physical bandwidth it's running at (100 Mbps), the 30 Mbps limitation will happen (downstream) within your ISP's network.

One issue with this, depending on the nature of your traffic, you network stats might show a higher transmission rate than what's achieved and/or some of your traffic could be dropped by your provider and that will be "invisible" to you.

If you platform supports it, you might consider "shaping" your traffic for 30 Mbps.