Comcast Ethernet Feed

Brian R. Watters brwatters at
Thu Mar 29 20:32:12 CDT 2012

Your correct with your understanding of our setup, I also note on our NPE-G1 that the onboard GIGE interface will auto-negotiation and I do see the flow control is not supported via the other side (Comcast) but as soon as I refresh and view the GIG# interface again I note that flow control is turned back on and "no negotiation auto" is back on the interface cfg ?, this is certainly part of the issue .. is their a way to disable flow control on the onboard GIGE ?  .. as stated Comcast does not want flow control on.

Yes there are other ports on this router that perform without issue and as designed both other GIGE interfaces that are VLAN'ed and Serial interfaces that are both DS3 and a PA-4T bonded to 6MEG's.

the GIGE cfg is as follows

interface GigabitEthernet0/1
 description Comcast Inet Feed Metro E 20MB
 bandwidth 100000
 ip address
 no ip unreachables
 no ip route-cache
 load-interval 30
 duplex full
 speed 100
 media-type rj45
 no negotiation auto
 no cdp enable

We have 2GB of memory on this router with a very light load on the CPU.

On 3/29/12 6:53 PM, Jon Lewis wrote:
> On Thu, 29 Mar 2012, Brielle Bruns wrote:
>> From my own experience here with our 7200s, some of the PA based
>> 100BaseT interfaces (ie: not on the IO module) can not negotiate
>> 100-full, but rather only half.  This leaves one end diff then the
>> other and creates issues with performance.  Try forcing both the
>> laptop and router to 100-full and see if it helps.
> Those interfaces don't to auto-negotiation at all.  That's why they
> default to 100 half.  OP said they were using a Gig interface though.
> Maybe a copper 10/100/1000 port on an NPE-G<1|2>?  I haven't used those,
> but I'd bet they support auto-negotiation.  1000baseT requires it.

I'm pretty sure the PA-FE-TX boards can do auto neg, just not 100 full 
(just tested with a 7507 with a VIP4 w a PA-FE-TX and a cheap 10BT hub - 
my 7206VXR is not powered up ATM).

Believe it has something to do with the DEC ethernet chip they use (I 
have an older desktop that just happens to have the same DEC chipset 
that those do and has exactly the same problem).

Based on what he said, I read his setup as having a G1 or G2 NPE, using 
the on-NPE gig to hook to comcast, and a PA-FE-TX in one of the PA slots.

At least, that's how it sounded to me - why else use 100BaseT on a gige 
as most laptops and desktops in the past... 4-5 years or so have onboard 

Brielle Bruns
The Summit Open Source Development Group    /

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