Recently I encounter Cisco switch 3750 reload puts it into switch: prompt. I try every possible troubleshoot but wherever switch reload its automatically boot to recovery mode.

This is happen because manually boot process is enable to yes.

test-sw4#sh boot
BOOT path-list:       flash:/c2950-i6k2l2q4-mz.121-22.EA12
Config file:          flash:/config.text
Private Config file:  flash:/private-config.text
Enable Break:         no
Manual Boot:          yes
*************Output Omitted****************

To set switch to boot automatically, we have to issue no boot command in global configuration mode.

test-sw4(config)#no boot manual ?
  <cr>
test-sw4(config)#no boot manual
test-sw4(config)#end
test-sw4#wr
Building configuration...
[OK]
test-sw4#

Verify the command.

test-sw4#sh boot
BOOT path-list:       flash:/c2950-i6k2l2q4-mz.121-22.EA12
Config file:          flash:/config.text
Private Config file:  flash:/private-config.text
Enable Break:         no
Manual Boot:          no
HELPER path-list:  
*****************Output Omitted****************

Other method
You can set it form the switch:prompt
Initial might be look like this. MANUAL_BOOT=yes

switch:setBOOT=flash:/c2950-i6k2l2q4-mz.121-22.EA12MANNUAL_BOOT=yesswtich:

switch:MANUAL_BOOT=no

In this lab we learn to configure access server. For this lab we are going to use Cisco 2511 router. Before configure the access server make sure you have connect console cable to the router and you can access the router.

Access_Server#sh ver
Cisco Internetwork Operating System Software
IOS (tm) 3000 Software (IGS-J-L), Version 11.0(18), RELEASE SOFTWARE (fc1)
Copyright (c) 1986-1997 by cisco Systems, Inc.
Compiled Mon 01-Dec-97 17:59 by jaturner
Image text-base: 0x03034C58, data-base: 0x00001000

Access_Server uptime is 3 hours, 45 minutes
System restarted by power-on
System image file is "flash:igs-j-l.110-18", booted via flash

cisco 2511 (68030) processor (revision M) with 14336K/2048K bytes of memory.
Processor board ID 10355024, with hardware revision 00000000
Bridging software.
SuperLAT software copyright 1990 by Meridian Technology Corp).
 --More--

Command reference

hostname Access_Server
!
enable secret 5 (deleted)
!
username cisco privilege 15 password 7 (deleted)
!
interface Loopback0
 ip address 172.16.1.1 255.255.255.0
!
interface Ethernet0
 ip address 10.10.10.10 255.255.255.0
 !
interface Serial0
 no ip address
 shutdown
 no fair-queue
!
interface Serial1
 no ip address
 shutdown
!
ip host Sw1 2001 172.16.1.1
ip host Sw2 2002 172.16.1.1
ip host Sw3 2003 172.16.1.1
ip host Sw4 2004 172.16.1.1
ip route 0.0.0.0 0.0.0.0 10.10.10.1

line con 0
line 1 16
 transport input all
line aux 0
 transport preferred telnet
 transport input all
 rxspeed 38400
 txspeed 38400
 flowcontrol hardware
line vty 0 4
 no login

ip host: to mapped name-to-address of the static host
    ip host (name)[tcp-port-number][address]
transport input: define a input protocol on the async lines to Telnet
    transport input all

Verify the command

Access_Server>sh ip interface brief
Interface        IP-Address      OK?  Method    Status                 Protocol
Ethernet0        10.10.10.10  YES  manual    up                     up     
Loopback0        172.16.1.1      YES  manual    up                     up     
Serial0          unassigned      YES  not set   administratively down  down   
Serial1          unassigned      YES  not set   administratively down  down   

Access_Server#sh host
Default domain is not set
Name/address lookup uses domain service
Name servers are 255.255.255.255

Host                     Flags      Age Type   Address(es)
cust215-20.classic.com.np(temp, OK)  0   IP    49.236.215.20
Sw1                      (perm, OK)  0   IP    172.16.1.1
Sw2                      (perm, OK)  3   IP    172.16.1.1
Sw3                      (perm, OK)  3   IP    172.16.1.1
Sw4                      (perm, OK)  3   IP    172.16.1.1
Access_Server#

Troubleshoot:

 Access_Server#sw2
Trying Sw2 (172.16.1.1, 2002)...
% Connection refused by remote host

Access_Server#clear line tty 2
[confirm]
 [OK]
Access_Server#sw2            
Trying Sw2 (172.16.1.1, 2002)... Open

Amnesiac (ttyu0)

login: