Shell Programming and Scripting

HI all
i need to connect to about 900 cisco routers and switch to do some configs changes. the issue i am having is that half the devices have one set of username and password and the other half have another username and password. From expect or bash script i can ssh into a device and make changes. I need a sript that will try and ssh into the device with user 1 and password, if it fails it must try and ssh with user2 name and password.

I am new to expect and bash, explination and help will greatly be appreciated.
my expect script so far:

Code:

#!/usr/bin/expect -f
# Define the input variable, this will be a routername.domain-name
set host "x.x.x.x" 
set timeout 8
# Define the login credentials we will use.
set username "xxxx" 
set password "!xxxx123" 
set usernamessh "eeeeee" 
set passwordssh "eeee123" 
# Ssh to host ip address
spawn ssh -q -o StrictHostKeyChecking=no $username@$host

expect {
timeout { send_user "\nFailed to get password prompt\n"; exit 1 }
eof { send_user "\nSSH failure for $hostname\n"; exit 1 }
"*assword"
}
# Send password if ssh is succesfull
send "$password\r"
# If Prompts *# not found, return login failed
expect {
timeout { send_user "\nLogin failed. Password incorrect.\n"; exit 1}
"*#"
}
interact

Moderator's Comments:

Please use code tags or face the wrath of Sauron.

# from here i need to add second ssh attempt to
#login to device using the second username and password..if
# the first ssh failed. please help i have no idea what to do now.