Skip to main content

Can I modify an access list in the production environment (VPN)?

With many VPN tunnels in your production environment you may be asked to modify some policies. What kind of tasks you can do without impact on the business traffic and what can be performed only during a change window?

You can add a new ACE, it doesn’t terminate tunnels:
 
R4(config-ext-nacl)#do sh runn | s access
ip access-list extended VPN
 permit ip host 150.1.4.4 20.0.0.0 0.0.0.255
R4(config-ext-nacl)#per
R4(config-ext-nacl)#permit ip
R4(config-ext-nacl)#permit ip 150.1.4.0 0.0.0.255  20.0.0.0 0.0.0.255
R4(config-ext-nacl)#
R4(config-ext-nacl)#

As you see nothing happened, but when you remove any entry, even not related with your SA you can see:
 
R4(config-ext-nacl)#do  sh run | s access
ip access-list extended VPN
 permit ip 150.1.4.0 0.0.0.255 20.0.0.0 0.0.0.255
 permit ip host 150.1.4.4 20.0.0.0 0.0.0.255
R4(config-ext-nacl)#
R4(config-ext-nacl)#no  permit ip 150.1.4.0 0.0.0.255 20.0.0.0 0.0.0.255
R4(config-ext-nacl)#
*Mar 15 10:41:16.123: IKEv2:(1): Sending DEL info message
*Mar 15 10:41:16.135: IKEv2:(1): Sending DEL info message
*Mar 15 10:41:16.167: IKEv2:(1): Processing ACK to informational exchange
*Mar 15 10:41:16.203: IKEv2:(1): Processing ACK to informational exchange
R4(config-ext-nacl)#
*Mar 15 10:41:18.691: IKEv2:(1): Processing initial message
*Mar 15 10:41:18.763: IKEv2:(1): Sending initial message
*Mar 15 10:41:18.899: IKEv2:(1): Recieved valid parameteres in process id
*Mar 15 10:41:18.923: IKEv2:(1): Processing auth message
*Mar 15 10:41:18.935: IKEv2:(1): Sending auth message
*Mar 15 10:41:18.947: IKEv2:(1): SA created; inserting SA into database
R4(config-ext-nacl)#

In this case our SA has been re-created once again. I strongly recommend to perform changes only during the change window but sometimes you may have an urgent request and it’s good to know which commands have impact on the active tunnels.
Labels:

Comments

Post a Comment

Popular posts from this blog

What should you know about HA 'override enabled' setting on Fortigate?

High availability is mandatory in most of today's network designs. Only very small companies or branches can run their business without redundancy. When you have Fortigate firewall in your network you have many options to increase network availability. You can use Fortigate Clustering Protocol ( FGCP ) or Virtual Router Redundancy Protocol ( VRRP ). FGCP has two modes: 'override' disabled (default) and 'override' enabled . I'm not going to explain how to set up HA as you can find many resources on Fortinet websites: https://cookbook.fortinet.com/high-availability-two-fortigates-56/ https://cookbook.fortinet.com/high-availability-with-fgcp-56/ Let's recap what is the main difference between them. The default HA setting is 'override' disabled and this is an order of selection an active unit: 1) number of monitored interfaces - when both units have the same number of working (up) interfaces check next parameter 2) HA uptime - an ...
8 comments
Read more

FortiGate and GRE tunnel

Recently I worked on one project where a client requested to re-route web traffic to the GRE tunnel to perform traffic inspection. I would like to share with you what is required if you configure it on FortiGate. We need a new GRE interface and policy base routing (PBR) to change the route for specific source IPs. Of course you need firewall policies to permit the traffic. Let's start with GRE interface. Unfortunately you can't configure it using the GUI, only CLI is the option: config system gre-tunnel edit "gre1" set interface "port1" set local-gw 55.55.55.55 set remote-gw 44.44.44.44 next end When the end peer is Cisco router, you need to set the IP for the GRE interface: config system interface edit gre1 set ip 192.168.10.10 255.255.255.255 set remote-ip192.168.10.20 end In next step we need to fix routing. We need the alternate path via GRE but to keep the route in the active routing table you need to set the same AD (adminis...
Post a Comment
Read more

Inpection of asymmetric sessions on FortiGate

There is one feature available on FortiGate, and I think you should know it, as it modifies a bit what we know about stateful firewalls. In past every packet was treated individually and you had to create policies in both directions. With stateful firewalls we can track connections, and by checking couple of attributes, we can treat them as part of the same session. For example when you initiate connection from a host1 to host2, the returning connection from host2 to host1 will be treated as part of the same connection (session). They have to have the same source/destination and destination/source IPs, port numbers and interfaces.There is an exception from this rule and FortiGate in some specific cases can accept connections on port which was not used in the initial connection. Let me explain how it works on the below example:      The host1 has a default gateway on R1 (10.0.1.2), but you may notice that it is not the optimal path to host2 subnet. When we analyze ...
1 comment
Read more