How to configure site-to-site VPN tunnel using ASA?

Site-to-Site secure VPN tunnel using the ASA (Adaptive Security Appliances) enables an encrypted connection between private networks over a public network such as the internet. 

Basic steps for VPN Configuration: 

1- First define the ISAKMP Policy.

For example:

•  Authentication
• Hash
• Encryption
• Group

2- Establish IPsec transform set.

For example:

 Ã‚·  Esp-des

• Esp-md5-hmac
• Esp-aes
• Asp-sha-hmac

3- Configure crypto access list.

For example:         Define interesting traffics

4- Configure crypto map

     Used to verify the previously defined parameters 

5- Now apply crypto map on the outside interface.

     Used to verify the outgoing interface traffic

Configuration of ASA on side A 

First defined the IKE polices on ASA-A 

ASA-A(config)#crypto isakmp policy 10

(10 is isakmp policy number) 

ASA-A(config-isakmp)#encryption des 

(enable encryption des) 

ASA-A(config-isakmp)#hash md5

(enable algorithm md5 for hashing) 

ASA-A(config-isakmp)#authentication pre-share

(enable Pre-shared method)

ASA-A(config-isakmp)#group 2   

(enable diffie-Helman group 2)    

ASA-A(config-isakmp)#exit  

(Exit from crypto isakmp mode)

• The next step is to create a pre-shared key (password) on ASA - A.

ASA-A(config)#crypto isakmp key office address 20.1.1.20

(Here Key is "office" and 20.1.1.20 is ASA - B Address)

• Now create an access list to define only interesting traffic.

ASA-A(config)#access-list 100 permit ip host 20.1.1.10 host 20.1.1.20

(100 is access list number and 20.1.1.10 is source address and 20.1.1.20 is destination address.) 

• Now create the transform-set for encryption and hashing.

ASA-A(config)#crypto ipsec transform-set ts2 esp-des esp-md5-hmac

(Here encryption type is des and hashing technique is md5-hmac)

ASA-A(config)#crypto map imap 10 ipsec-isakmp 

(crypto map name imap) 

ASA-A(config)# crypto map imap 10 match address 100   

(apply the access list)

ASA-A(config)# crypto map imap 10 set transform-set ts2

(apply the transform set) 

ASA-A(config)# crypto map imap 10 set peer 20.1.1.20 

(Set remote peer address)

• Now apply the crypto map to the ASA - A interface

ASA-A(config)# crypto map imap interface outside

 (Apply crypto map on outside interface)

ASA-A(config)# crypto isakmp enable outside

(To enable crypto isakmp on ASA)

 

Configuration of ASA on side B 

First defined the IKE polices on ASA-B 

ASA-B(config)#crypto isakmp policy 10

(10 is isakmp policy number) 

ASA-B(config-isakmp)#encryption des 

(enable encryption des) 

ASA-B(config-isakmp)#hash md5

(enable algorithm md5 for hashing) 

ASA-B(config-isakmp)#authentication pre-share

(enable Pre-shared method)

ASA-B(config-isakmp)#group 2   

(enable diffie-Helman group 2)    

ASA-B(config-isakmp)#exit  

(Exit from crypto isakmp mode)

• The next step is to create a pre-shared key (password) on ASA - B.

ASA-B(config)#crypto isakmp key office address 20.1.1.10

(Here Key is "office" and 20.1.1.10 is ASA - A Address)

• Now create an access list to define only interesting traffic.

ASA-B(config)#access-list 100 permit ip host 20.1.1.20 host 20.1.1.10

(100 is access list number and 20.1.1.20 is source address and 20.1.1.10 is destination address.) 

• Now create the transform-set for encryption and hashing.

ASA-B(config)#crypto ipsec transform-set ts2 esp-des esp-md5-hmac

(Here encryption type is des and hashing technique is md5-hmac)

ASA-B(config)#crypto map imap 10 ipsec-isakmp 

(crypto map name imap) 

ASA-B(config)# crypto map imap 10 match address 100   

(apply the access list)

ASA-B(config)# crypto map imap 10 set transform-set ts2

(apply the transform set) 

ASA-B(config)# crypto map imap 10 set peer 20.1.1.10 

(Set remote peer address)

• Now apply the crypto map to the ASA - B outside interface

ASA-B(config)# crypto map imap interface outside 

(Apply crypto map on outside interface)

ASA-B(config)# crypto isakmp enable outside

(To enable crypto isakmp on ASA) 

Now to verify the secure tunnel, ping to other remote location. 

ASA-B(config)# ping 20.1.1.10

Thanks & regards,

"Remember Me When You Raise Your Hand For Dua"
Raheel Ahmed Khan
System Engineer
send2raheel@yahoo.com
send2raheel@engineer.com
sirraheel@gmail.com
send2raheel (skype id)

My Blog Spot
http://raheel-mydreamz.blogspot.com/
http://raheeldreamz.wordpress.com/

My Face book pages
http://www.facebook.com/pages/My-Dreamz-Rebiuld-our-nation/176215539101271    @[176215539101271:0]    
http://www.facebook.com/pages/Beauty-of-islam/223983470988333?sk=wall            @[223983470988333:0]               
http://www.facebook.com/pages/Health-is-wealth/289486761065829?sk=wall            @[289486761065829:0]