The A/S interface is essentially a synchronous interface, but can be turned into an asynchronous interface via "physical-layer async" command. So, yes you can connect the routers back-to-back. CM -----Original Message----- From: Thomas To: [EMAIL PROTECTED] Sent: 12/05/01 06:35 Subject: difference between synchronous and asynchronous serial ports [7:4255] Hi All - I am looking for some routers to setup my CCNP lab. The Cisco 2522 seems to be a great for Frame Relay switch if I can use crossover cable with the A/S serial ports. However, I am not sure if the A/S will be acting exactly the same as the synchronous serial port? Can I connect these asynchromous serial port to a synchronous serial port on a 2501 router using crossover cable? Thanks all in advance! FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=4259&t=4259 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]