Err apt-get update on Ubuntu 14.04

I am noticing the below errors when I try to do update on Ubuntu 14.04 machine. I remember it was working fine the last time I tried.

sudo apt-get update
Err http://extras.ubuntu.com trusty InRelease                                  

Err http://extras.ubuntu.com trusty Release.gpg                                
  Cannot initiate the connection to extras.ubuntu.com:80 (2001:67c:1360:8c01::23). - connect (101: Network is unreachable) [IP: 2001:67c:1360:8c01::23 80]
Err http://us.archive.ubuntu.com trusty InRelease                              

Err http://us.archive.ubuntu.com trusty-updates InRelease                      

Err http://us.archive.ubuntu.com trusty-backports InRelease                    

Err http://us.archive.ubuntu.com trusty-proposed InRelease                     

Err http://us.archive.ubuntu.com trusty Release.gpg                            
  Cannot initiate the connection to us.archive.ubuntu.com:80 (2001:67c:1562::15). - connect (101: Network is unreachable) [IP: 2001:67c:1562::15 80]
Err http://us.archive.ubuntu.com trusty-updates Release.gpg
  Cannot initiate the connection to us.archive.ubuntu.com:80 (2001:67c:1562::15). - connect (101: Network is unreachable) [IP: 2001:67c:1562::15 80]
Err http://us.archive.ubuntu.com trusty-backports Release.gpg
  Cannot initiate the connection to us.archive.ubuntu.com:80 (2001:67c:1562::15). - connect (101: Network is unreachable) [IP: 2001:67c:1562::15 80]
Err http://us.archive.ubuntu.com trusty-proposed Release.gpg
  Cannot initiate the connection to us.archive.ubuntu.com:80 (2001:67c:1562::15). - connect (101: Network is unreachable) [IP: 2001:67c:1562::15 80]
Err http://security.ubuntu.com trusty-security InRelease

Err http://security.ubuntu.com trusty-security Release.gpg
  Cannot initiate the connection to security.ubuntu.com:80 (2001:67c:1562::17). - connect (101: Network is unreachable) [IP: 2001:67c:1562::17 80]
Reading package lists... Done
W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty/InRelease  

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-updates/InRelease  

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-backports/InRelease  

W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/trusty-security/InRelease  

W: Failed to fetch http://extras.ubuntu.com/ubuntu/dists/trusty/InRelease  

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-proposed/InRelease  

W: Failed to fetch http://extras.ubuntu.com/ubuntu/dists/trusty/Release.gpg  Cannot initiate the connection to extras.ubuntu.com:80 (2001:67c:1360:8c01::23). - connect (101: Network is unreachable) [IP: 2001:67c:1360:8c01::23 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty/Release.gpg  Cannot initiate the connection to us.archive.ubuntu.com:80 (2001:67c:1562::15). - connect (101: Network is unreachable) [IP: 2001:67c:1562::15 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-updates/Release.gpg  Cannot initiate the connection to us.archive.ubuntu.com:80 (2001:67c:1562::15). - connect (101: Network is unreachable) [IP: 2001:67c:1562::15 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-backports/Release.gpg  Cannot initiate the connection to us.archive.ubuntu.com:80 (2001:67c:1562::15). - connect (101: Network is unreachable) [IP: 2001:67c:1562::15 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-proposed/Release.gpg  Cannot initiate the connection to us.archive.ubuntu.com:80 (2001:67c:1562::15). - connect (101: Network is unreachable) [IP: 2001:67c:1562::15 80]

W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/trusty-security/Release.gpg  Cannot initiate the connection to security.ubuntu.com:80 (2001:67c:1562::17). - connect (101: Network is unreachable) [IP: 2001:67c:1562::17 80]

W: Some index files failed to download. They have been ignored, or old ones used instead.

Can some body help me out to fix this please !

@TungTran: After your suggested change, there is some progress but, am still facing some issues as shown below:

sudo apt-get update
Ign http://us.archive.ubuntu.com trusty InRelease                              
Ign http://security.ubuntu.com trusty-security InRelease            
Ign http://extras.ubuntu.com trusty InRelease 
Ign http://security.ubuntu.com trusty-security Release.gpg
Ign http://us.archive.ubuntu.com trusty-updates InRelease
Ign http://extras.ubuntu.com trusty Release.gpg
Ign http://security.ubuntu.com trusty-security Release
Ign http://us.archive.ubuntu.com trusty-backports InRelease
Ign http://extras.ubuntu.com trusty Release                                    
Ign http://us.archive.ubuntu.com trusty-proposed InRelease                     
Ign http://us.archive.ubuntu.com trusty Release.gpg                  
Ign http://us.archive.ubuntu.com trusty-updates Release.gpg                    
Ign http://us.archive.ubuntu.com trusty-backports Release.gpg        
Ign http://us.archive.ubuntu.com trusty-proposed Release.gpg         
Ign http://us.archive.ubuntu.com trusty Release                                
Ign http://us.archive.ubuntu.com trusty-updates Release              
Ign http://us.archive.ubuntu.com trusty-backports Release            
Ign http://us.archive.ubuntu.com trusty-proposed Release             
Err http://extras.ubuntu.com trusty/main Sources                     
  404  Not Found [IP: 199.168.148.24 80]
Err http://extras.ubuntu.com trusty/main i386 Packages                         
  404  Not Found [IP: 199.168.148.24 80]
Ign http://extras.ubuntu.com trusty/main Translation-en_US                     
Ign http://extras.ubuntu.com trusty/main Translation-en              
Err http://security.ubuntu.com trusty-security/main Sources                  
  404  Not Found [IP: 199.168.151.24 80]
Err http://security.ubuntu.com trusty-security/restricted Sources
  404  Not Found [IP: 199.168.151.24 80]
Err http://security.ubuntu.com trusty-security/universe Sources
  404  Not Found [IP: 199.168.151.24 80]
Err http://security.ubuntu.com trusty-security/multiverse Sources
  404  Not Found [IP: 199.168.151.24 80]
Err http://security.ubuntu.com trusty-security/main i386 Packages
  404  Not Found [IP: 199.168.151.24 80]
Err http://security.ubuntu.com trusty-security/restricted i386 Packages
  404  Not Found [IP: 199.168.151.24 80]
Err http://security.ubuntu.com trusty-security/universe i386 Packages
  404  Not Found [IP: 199.168.151.24 80]
Err http://security.ubuntu.com trusty-security/multiverse i386 Packages
  404  Not Found [IP: 199.168.151.24 80]
Ign http://security.ubuntu.com trusty-security/main Translation-en_US
Ign http://security.ubuntu.com trusty-security/main Translation-en
Ign http://security.ubuntu.com trusty-security/multiverse Translation-en_US
Ign http://security.ubuntu.com trusty-security/multiverse Translation-en
Ign http://security.ubuntu.com trusty-security/restricted Translation-en_US  
Ign http://security.ubuntu.com trusty-security/restricted Translation-en     
Ign http://security.ubuntu.com trusty-security/universe Translation-en_US    
Ign http://security.ubuntu.com trusty-security/universe Translation-en
Err http://us.archive.ubuntu.com trusty/main Sources   
  404  Not Found [IP: 199.168.148.24 80]
Err http://us.archive.ubuntu.com trusty/restricted Sources
  404  Not Found [IP: 199.168.148.24 80]
Err http://us.archive.ubuntu.com trusty/universe Sources
  404  Not Found [IP: 199.168.148.24 80]
Err http://us.archive.ubuntu.com trusty/multiverse Sources
  404  Not Found [IP: 199.168.148.24 80]
Err http://us.archive.ubuntu.com trusty/main i386 Packages
  404  Not Found [IP: 199.168.148.24 80]
Err http://us.archive.ubuntu.com trusty/restricted i386 Packages
  404  Not Found [IP: 199.168.148.24 80]
Err http://us.archive.ubuntu.com trusty/universe i386 Packages
  404  Not Found [IP: 199.168.148.24 80]
Err http://us.archive.ubuntu.com trusty/multiverse i386 Packages
  404  Not Found [IP: 199.168.148.24 80]
Ign http://us.archive.ubuntu.com trusty/main Translation-en_US
Ign http://us.archive.ubuntu.com trusty/main Translation-en
Ign http://us.archive.ubuntu.com trusty/multiverse Translation-en_US
Ign http://us.archive.ubuntu.com trusty/multiverse Translation-en
Ign http://us.archive.ubuntu.com trusty/restricted Translation-en_US
Ign http://us.archive.ubuntu.com trusty/restricted Translation-en
Ign http://us.archive.ubuntu.com trusty/universe Translation-en_US
Ign http://us.archive.ubuntu.com trusty/universe Translation-en
Err http://us.archive.ubuntu.com trusty-updates/main Sources
  404  Not Found [IP: 199.168.148.24 80]
Err http://us.archive.ubuntu.com trusty-updates/restricted Sources
  404  Not Found [IP: 199.168.148.24 80]
Err http://us.archive.ubuntu.com trusty-updates/universe Sources
  404  Not Found [IP: 199.168.148.24 80]
Err http://us.archive.ubuntu.com trusty-updates/multiverse Sources
  404  Not Found [IP: 199.168.148.24 80]
Err http://us.archive.ubuntu.com trusty-updates/main i386 Packages
  404  Not Found [IP: 199.168.148.24 80]
Err http://us.archive.ubuntu.com trusty-updates/restricted i386 Packages
  404  Not Found [IP: 199.168.148.24 80]
Err http://us.archive.ubuntu.com trusty-updates/universe i386 Packages
  404  Not Found [IP: 199.168.148.24 80]
Err http://us.archive.ubuntu.com trusty-updates/multiverse i386 Packages
  404  Not Found [IP: 199.168.148.24 80]
Ign http://us.archive.ubuntu.com trusty-updates/main Translation-en_US
Ign http://us.archive.ubuntu.com trusty-updates/main Translation-en
Ign http://us.archive.ubuntu.com trusty-updates/multiverse Translation-en_US
Ign http://us.archive.ubuntu.com trusty-updates/multiverse Translation-en
Ign http://us.archive.ubuntu.com trusty-updates/restricted Translation-en_US
Ign http://us.archive.ubuntu.com trusty-updates/restricted Translation-en
Ign http://us.archive.ubuntu.com trusty-updates/universe Translation-en_US
Ign http://us.archive.ubuntu.com trusty-updates/universe Translation-en
Err http://us.archive.ubuntu.com trusty-backports/main Sources
  404  Not Found [IP: 199.168.148.24 80]
Err http://us.archive.ubuntu.com trusty-backports/restricted Sources
  404  Not Found [IP: 199.168.148.24 80]
Err http://us.archive.ubuntu.com trusty-backports/universe Sources
  404  Not Found [IP: 199.168.148.24 80]
Err http://us.archive.ubuntu.com trusty-backports/multiverse Sources
  404  Not Found [IP: 199.168.148.24 80]
Err http://us.archive.ubuntu.com trusty-backports/main i386 Packages
  404  Not Found [IP: 199.168.148.24 80]
Err http://us.archive.ubuntu.com trusty-backports/restricted i386 Packages
  404  Not Found [IP: 199.168.148.24 80]
Err http://us.archive.ubuntu.com trusty-backports/universe i386 Packages
  404  Not Found [IP: 199.168.148.24 80]
Err http://us.archive.ubuntu.com trusty-backports/multiverse i386 Packages
  404  Not Found [IP: 199.168.148.24 80]
Ign http://us.archive.ubuntu.com trusty-backports/main Translation-en_US
Ign http://us.archive.ubuntu.com trusty-backports/main Translation-en
Ign http://us.archive.ubuntu.com trusty-backports/multiverse Translation-en_US
Ign http://us.archive.ubuntu.com trusty-backports/multiverse Translation-en
Ign http://us.archive.ubuntu.com trusty-backports/restricted Translation-en_US
Ign http://us.archive.ubuntu.com trusty-backports/restricted Translation-en
Ign http://us.archive.ubuntu.com trusty-backports/universe Translation-en_US
Ign http://us.archive.ubuntu.com trusty-backports/universe Translation-en
Err http://us.archive.ubuntu.com trusty-proposed/multiverse i386 Packages
  404  Not Found [IP: 199.168.148.24 80]
Err http://us.archive.ubuntu.com trusty-proposed/main i386 Packages
  404  Not Found [IP: 199.168.148.24 80]
Err http://us.archive.ubuntu.com trusty-proposed/universe i386 Packages
  404  Not Found [IP: 199.168.148.24 80]
Err http://us.archive.ubuntu.com trusty-proposed/restricted i386 Packages
  404  Not Found [IP: 199.168.148.24 80]
Ign http://us.archive.ubuntu.com trusty-proposed/main Translation-en_US
Ign http://us.archive.ubuntu.com trusty-proposed/main Translation-en
Ign http://us.archive.ubuntu.com trusty-proposed/multiverse Translation-en_US
Ign http://us.archive.ubuntu.com trusty-proposed/multiverse Translation-en
Ign http://us.archive.ubuntu.com trusty-proposed/restricted Translation-en_US
Ign http://us.archive.ubuntu.com trusty-proposed/restricted Translation-en
Ign http://us.archive.ubuntu.com trusty-proposed/universe Translation-en_US
Ign http://us.archive.ubuntu.com trusty-proposed/universe Translation-en
W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/trusty-security/main/source/Sources  404  Not Found [IP: 199.168.151.24 80]

W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/trusty-security/restricted/source/Sources  404  Not Found [IP: 199.168.151.24 80]

W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/trusty-security/universe/source/Sources  404  Not Found [IP: 199.168.151.24 80]

W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/trusty-security/multiverse/source/Sources  404  Not Found [IP: 199.168.151.24 80]

W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/trusty-security/main/binary-i386/Packages  404  Not Found [IP: 199.168.151.24 80]

W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/trusty-security/restricted/binary-i386/Packages  404  Not Found [IP: 199.168.151.24 80]

W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/trusty-security/universe/binary-i386/Packages  404  Not Found [IP: 199.168.151.24 80]

W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/trusty-security/multiverse/binary-i386/Packages  404  Not Found [IP: 199.168.151.24 80]

W: Failed to fetch http://extras.ubuntu.com/ubuntu/dists/trusty/main/source/Sources  404  Not Found [IP: 199.168.148.24 80]

W: Failed to fetch http://extras.ubuntu.com/ubuntu/dists/trusty/main/binary-i386/Packages  404  Not Found [IP: 199.168.148.24 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty/main/source/Sources  404  Not Found [IP: 199.168.148.24 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty/restricted/source/Sources  404  Not Found [IP: 199.168.148.24 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty/universe/source/Sources  404  Not Found [IP: 199.168.148.24 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty/multiverse/source/Sources  404  Not Found [IP: 199.168.148.24 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty/main/binary-i386/Packages  404  Not Found [IP: 199.168.148.24 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty/restricted/binary-i386/Packages  404  Not Found [IP: 199.168.148.24 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty/universe/binary-i386/Packages  404  Not Found [IP: 199.168.148.24 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty/multiverse/binary-i386/Packages  404  Not Found [IP: 199.168.148.24 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-updates/main/source/Sources  404  Not Found [IP: 199.168.148.24 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-updates/restricted/source/Sources  404  Not Found [IP: 199.168.148.24 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-updates/universe/source/Sources  404  Not Found [IP: 199.168.148.24 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-updates/multiverse/source/Sources  404  Not Found [IP: 199.168.148.24 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-updates/main/binary-i386/Packages  404  Not Found [IP: 199.168.148.24 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-updates/restricted/binary-i386/Packages  404  Not Found [IP: 199.168.148.24 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-updates/universe/binary-i386/Packages  404  Not Found [IP: 199.168.148.24 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-updates/multiverse/binary-i386/Packages  404  Not Found [IP: 199.168.148.24 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-backports/main/source/Sources  404  Not Found [IP: 199.168.148.24 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-backports/restricted/source/Sources  404  Not Found [IP: 199.168.148.24 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-backports/universe/source/Sources  404  Not Found [IP: 199.168.148.24 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-backports/multiverse/source/Sources  404  Not Found [IP: 199.168.148.24 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-backports/main/binary-i386/Packages  404  Not Found [IP: 199.168.148.24 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-backports/restricted/binary-i386/Packages  404  Not Found [IP: 199.168.148.24 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-backports/universe/binary-i386/Packages  404  Not Found [IP: 199.168.148.24 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-backports/multiverse/binary-i386/Packages  404  Not Found [IP: 199.168.148.24 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-proposed/multiverse/binary-i386/Packages  404  Not Found [IP: 199.168.148.24 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-proposed/main/binary-i386/Packages  404  Not Found [IP: 199.168.148.24 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-proposed/universe/binary-i386/Packages  404  Not Found [IP: 199.168.148.24 80]

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-proposed/restricted/binary-i386/Packages  404  Not Found [IP: 199.168.148.24 80]

E: Some index files failed to download. They have been ignored, or old ones used instead.

This is the content of my sources.list

cat /etc/apt/sources.list
# deb cdrom:[Ubuntu 14.04.3 LTS _Trusty Tahr_ - Beta i386 (20150805)]/ trusty main restricted

# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb http://us.archive.ubuntu.com/ubuntu/ trusty main restricted
deb-src http://us.archive.ubuntu.com/ubuntu/ trusty main restricted

## Major bug fix updates produced after the final release of the
## distribution.
deb http://us.archive.ubuntu.com/ubuntu/ trusty-updates main restricted
deb-src http://us.archive.ubuntu.com/ubuntu/ trusty-updates main restricted

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
deb http://us.archive.ubuntu.com/ubuntu/ trusty universe
deb-src http://us.archive.ubuntu.com/ubuntu/ trusty universe
deb http://us.archive.ubuntu.com/ubuntu/ trusty-updates universe
deb-src http://us.archive.ubuntu.com/ubuntu/ trusty-updates universe

## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu 
## team, and may not be under a free licence. Please satisfy yourself as to 
## your rights to use the software. Also, please note that software in 
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb http://us.archive.ubuntu.com/ubuntu/ trusty multiverse
deb-src http://us.archive.ubuntu.com/ubuntu/ trusty multiverse
deb http://us.archive.ubuntu.com/ubuntu/ trusty-updates multiverse
deb-src http://us.archive.ubuntu.com/ubuntu/ trusty-updates multiverse

## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
deb http://us.archive.ubuntu.com/ubuntu/ trusty-backports main restricted universe multiverse
deb-src http://us.archive.ubuntu.com/ubuntu/ trusty-backports main restricted universe multiverse

deb http://security.ubuntu.com/ubuntu trusty-security main restricted
deb-src http://security.ubuntu.com/ubuntu trusty-security main restricted
deb http://security.ubuntu.com/ubuntu trusty-security universe
deb-src http://security.ubuntu.com/ubuntu trusty-security universe
deb http://security.ubuntu.com/ubuntu trusty-security multiverse
deb-src http://security.ubuntu.com/ubuntu trusty-security multiverse

## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
# deb http://archive.canonical.com/ubuntu trusty partner
# deb-src http://archive.canonical.com/ubuntu trusty partner

## This software is not part of Ubuntu, but is offered by third-party
## developers who want to ship their latest software.
deb http://extras.ubuntu.com/ubuntu trusty main
deb http://us.archive.ubuntu.com/ubuntu/ trusty-proposed multiverse main universe restricted
deb-src http://extras.ubuntu.com/ubuntu trusty main

Solution 1:

Create /etc/apt/apt.conf to add proxy configuration for APT.

sudo nano /etc/apt/apt.conf

Add this line to your /etc/apt/apt.conf file

Acquire::http::Proxy "http://proxyaddress:proxyport";

Save it with Ctrl+X, Y and retry:

sudo apt-get update