mac addresses errors on router and switches

[africanDrew]

hello my fellow networks i was given PT Activity 1.5.1:
Packet Tracer Skills Integration Challenge to configure when i reached on the step of adding a 1841 router and adding the serial port. I added the both but on checking the serial interface has no Mac address (no set ) the same on switches help me out i asked my Instructor he told me that the packet tracer version  I'm  using might be the issue version 8.1.1 and told me to config the static mac address 

[Martin L · Accepted solution]

Serial interfaces have NO Mac addresses, you cannot add serial interface to a switch.  MACs are needed for PC, routers, switches, etc for all Ethernet ports /interfaces which have ARPA encapsulation;  Default Encapsulation for serial interface is HDLC on Cisco routers.  Ethernet communication uses MACs but not serial HDLC or PPP.

Regards, ML
**Please Rate All Helpful Responses **

[africanDrew]

thx brother for the help nut all i noticed is that packet tracer v 8.1.1 has some errors with configuring old activites