Warning message

  • Cisco Support Forums is in Read Only mode while the site is being migrated.
  • Cisco Support Forums is in Read Only mode while the site is being migrated.

256kbps link on Sync/Async serial interfaces...

Unanswered Question
Oct 16th, 2002
User Badges:
  • Bronze, 100 points or more

Hi all,

As per cisco docment, Sync/Async serial interfaces support max of 128Kbps. But for temporary lack of high speed ports, we have given 256Kbps customer through sync/async interface. During observation, due to his huge traffic , the 5 minute output rate (at our end) crosses 128 and almost it has reached 254Kbps. I expected after crossing 128kbps, there should be packet drops but didn't receive any complaint from customer. So, is that correct to use 256Kbps links, to use sync/async interfaces.

Thanks in advance..



  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
mark-obrien Wed, 10/16/2002 - 13:03
User Badges:
  • Bronze, 100 points or more


I think you got lucky. The manufacurer specified a "design" maximum data rate. As is often the case, the actual maximum exceeds the design rate. In this instance, the actual rate almost doubled the design rate, but I wouldn't count on this being the case in the future.

I don't have any specific knowledge of how Cisco, or the manufacurer of this interface, has designed the card, but this is often the case when a spec is given in product literature.

Hope this helps.


We have Cisco 2600 routers here with the sync/async interfaces and we frequently have 256K customers using these interfaces. We have had no problems with complaints. It is slower, of course, but we have experienced no packet drops. I suspect it kind of works like a computer; for example, a fast disk drive can be hampered by a bus with a low bandwidth, but it will still work.


This Discussion