cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
17825
Views
15
Helpful
7
Comments
Artem Tkachov
Beginner
Beginner

Introduction:

Purpose of this document is to show the way how you can monitor your remote ASA over Ipsec  Lan-to-Lan tunnel.

Scenario:

In my case I’ll try to use a common scenario, where you have HQ ASA and branch ASA which should be monitored/polled over VPN tunnel (which is in between). SNMP/NMS server will be behind the HQ ASA. In my test I will try to monitor/poll interface fastEthernet 0/0 on Branch ASA from SNMP/NMS Server.

NMS/SNMP server: 192.168.1.3/24

Branch ASA FastEthernet 0/0: 5.5.5.1/24

Topology:

Topo.jpg

Solution:

VPN configuration part:

On Branch ASA:

...

crypto ipsec ikev1 transform-set TRANS esp-3des esp-sha-hmac

...

crypto map MAP 10 match address ACL

crypto map MAP 10 set peer $peer ip address$

crypto map MAP 10 set ikev1 transform-set TRANS

crypto map MAP interface outside

crypto ikev1 enable outside

...

tunnel-group $peer ip address$ type ipsec-l2l

tunnel-group $peer ip address$ ipsec-attributes

ikev1 pre-shared-key cisco

...

crypto ikev1 policy 1

authentication pre-share

encryption 3des

hash sha

group 2

lifetime 28800

...

In ACL for encryption you should have ip address/subnet of fastethernet interface 0/0 (or whatever)

# access-list ACL extended permit ip 5.5.5.0 255.255.255.0 192.168.1.0 255.255.255.0

On HQ ASA:

...

crypto ipsec ikev1 transform-set TRANS esp-3des esp-sha-hmac

...

crypto map MAP 10 match address ACL

crypto map MAP 10 set peer $peer ip address$

crypto map MAP 10 set ikev1 transform-set TRANS

crypto map MAP interface outside

crypto ikev1 enable outside

...

crypto ikev1 policy 1

authentication pre-share

encryption 3des

hash sha

group 2

lifetime 28800

...

tunnel-group $peer ip address$ type ipsec-l2l

tunnel-group $peer ip address$ ipsec-attributes

ikev1 pre-shared-key cisco

In ACL for encryption should be defined ip address/subnet of NMS/SNMP server.

# access-list ACL extended permit ip 192.168.1.0 255.255.255.0 5.5.5.0 255.255.255.0

SNMP part:

On Branch ASA:

1.   You need to configure SNMP server and define interface behind which server is located, and this is a tricky part, since you need to define “inside” interface in order to push snmp traffic over the tunnel:

          # snmp-server host inside 192.168.1.3 community test version 2c

2.       You need to configure your “inside” interface as “management-access”.

          # management-access inside

Verification:

I’ve  done verification with “snmpwalk” command from snmp server:

root@VM:~# snmpwalk -v 2c -c test 5.5.5.1

iso.3.6.1.2.1.1.1.0 = STRING: "Cisco Adaptive Security Appliance Version 8.4(2)"

iso.3.6.1.2.1.1.2.0 = OID: iso.3.6.1.4.1.9.1.227

iso.3.6.1.2.1.1.3.0 = Timeticks: (134200) 0:22:22.00

iso.3.6.1.2.1.1.4.0 = ""

iso.3.6.1.2.1.1.6.0 = ""

iso.3.6.1.2.1.1.7.0 = INTEGER: 4

iso.3.6.1.2.1.2.1.0 = INTEGER: 8

iso.3.6.1.2.1.2.2.1.1.2 = INTEGER: 2

iso.3.6.1.2.1.2.2.1.1.3 = INTEGER: 3

iso.3.6.1.2.1.2.2.1.1.4 = INTEGER: 4

Reference links:

1.       http://www.cisco.com/en/US/products/ps6120/products_tech_note09186a00807e0aca.shtml

2.       http://www.cisco.com/en/US/products/hw/vpndevc/ps2030/products_tech_note09186a0080094a13.shtml

3.       http://www.cisco.com/en/US/docs/security/pix/pix72/quick/guide/sitvpn_p.html

Comments
joe.ho
Beginner
Beginner

I am following the example above to setup the snmp over vpn. It is not working for me. After doing some research, I found the route-lookup command is needed on my NAT command. 

 

nat (INSIDE,OUTSIDE) source static LOCAL-NETS LOCAL-NETS destination static REMOTE-NETS REMOTE-NETS route-lookup

 

Reference link

https://www.tunnelsup.com/cisco-asa-drop-reason-unexpected-packet/

CSCO11805675
Beginner
Beginner

I am tryign to do exactly what is described here. I already have route lookup enable on my NAT. I can not get SNMP or SMTP traffic from the ASA itself (hosts behind the firewall work fine) to Hit servers on the other side of the VPN. It gets blovked by implicit rule accorfing to packet trace.

netadminquid
Beginner
Beginner

I had an ASA with SNMP polling from a remote site through VPN tunnel running for a long.
After the ASA software upgrade to version 9.14.2 SNMP polling stopped working.
It keeps to work fine from hosts residing on inside network.

jont717
Beginner
Beginner

Same issue here.  SNMP to a firewall over site-to-site VPN broke on new code.  Works fine for anything behind the firewall in the remote location. 

romandoroshchuk
Beginner
Beginner

Same issue on ASA version 9.16.2, not fixed.

drew000
Beginner
Beginner

Build the IP address for the "outside" interface on the branch ASA into the VPN site-to-site crypto map to tunnel the SNMP traffic through the tunnel. Not a bug, a new feature.

 

New feature added to version 9.14(2) in November, 2020. https://www.cisco.com/c/en/us/td/docs/security/asa/asa914/release/notes/asarn914.html#reference_xqs_mvp_xhb

SNMP polling over site-to-site VPN

For secure SNMP polling over a site-to-site VPN, include the IP address of the outside interface in the crypto map access-list as part of the VPN configuration.

 

 

Setup the NMS/SNMP server to monitor the "outside" IP address instead of the "inside" IP address on the branch ASA.  The traffic will be secured by traversing the site-to-site tunnel. 

 

From the above scenario; changes:

On Branch ASA:

access-list ACL extended permit ip host 198.51.100.1 host 192.168.1.3
access-list ACL extended permit ip 5.5.5.0 255.255.255.0 192.168.1.0 255.255.255.0

 

On HQ ASA:

access-list ACL extended permit ip host 192.168.1.3 host 198.51.100.1
access-list ACL extended permit ip 192.168.1.0 255.255.255.0 5.5.5.0 255.255.255.0

 

I have it working again after v9.14 update. 

 

netadminquid
Beginner
Beginner

In my case I have VPN set up using VTI and not crypto map, so do I have to route OUTSIDE interface through the tunnel?

 

In any way this is not optimal in situation where OUTSIDE interface has to be reached not throug vpn, for instance Anyconnect or remote management from branch or HQ.

Getting Started

Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community:

Quick Links