[c-nsp] Lot of input errors on a NPE-G1 interface

[Mark Tinka]

On Wednesday, May 23, 2012 09:23:03 PM Matlock, Kenneth L 
wrote:

> " hubs, concentrators,  switches, bridges, etc... to this
> interface when portfast is enabled, can cause temporary
> bridging loops."
> 
> Those are all Layer 2 devices. A router is a layer 3
> device (unless you explicitly turn bridging on).

We disable Portfast for all 802.1Q trunks, regardless of 
whether they're going to routers or switches. 

If an engineer moves connections by mistake, or plugs the 
trunk from the switch into another switch by mistake, 
instead of a router, you have that protection.

The 50-odd seconds required for the STP state machine to 
raech a Forwarding situation is a small price to pay for 
this safety, in my opinion (Lord knows how many times we've 
been saved by blocking Edge ports on BPDU receipt). 

Of course, the topologies have a part to play in one's 
thought process; if there is redundancy between the switches 
and their uplink routers, it's not such a big deal. But if 
services that rely on things like TFTP or DHCP are of 
importance, one has to rethink this for their network.

Mark.