12 May

Interfaces are important in ASAv failover on VIRL

Failover link on ASAv must be created using interface GigabitEthernet0/8

One reader asked me few days ago following question when he had problem establishing the failover in his lab: “I’ve tried to create ASA failover pair on VIRL and it was not working. I’ve looked through manual and VIRL forum for the solution. I believe that failover is supported configuration on VIRL. I think my configuration is correct, nodes can ping each other but I still cannot establish failover relationship”. Configuration he made was correct except he forgot about one thing – interfaces numbers are important when you setup failover using ASAv.

Cisco VIRL uses ASAv image for virtual firewalls. This is same image that you use in production on ESXi. That means all restrictions applies also to virtual firewall if you run it on VIRL. In this image we must configure failover link using interfaces GigabitEthernet0/8. It’s clearly stated in documentation. If we use any other interface the configuration will be accepted but failover never established.


failover lan unit primary
failover lan interface Fail-link GigabitEthernet0/8
failover replication http
failover link State-link GigabitEthernet0/7
failover interface ip Fail-link 192.168.255.253 255.255.255.252 standby 192.168.255.254
failover interface ip State-link 192.168.254.253 255.255.255.252 standby 192.168.254.254
failover ipsec pre-shared-key 0 FailoverKey
failover

We also need to remember we can’t configure Active-Active failover. This mode is not supported so we have to stick to Active-Standby model. It’s direct result of lack of support for virtual contexts so remember about it as well.

05 Mar

ASAv on Amazon Web Services – login issues

Have you ever tried to run ASAv image on Amazon Web Services (AWS)? Yes, in Marketplace you will find supported image of this firewall (which is actually great thing because you can run it in BYOB model where you use unlicensed mode for testing the features. Same way as you can do on your ESXi.

Deployment is easy with the creator of EC2 instance, just few clicks and there it is. Except small problem – on latest release of 9.6.2.1 I was not able to connect to management interface via SSH. It should be possible by using key assigned to instance during creation but no matter what I’ve done it always asked for password.

There is small but nice workaround of this problem that also enables HTTPS access to ASAv. During the instance deployment we should put zero-day configuration that will be implemented on ASA. In documentation we even have proposal on such config which we further modify by adding HTTP/HTTPS access, additional user account, enable password and aaa local authentication.

The final zero-day configuration should look as below


interface management0/0
management-only
nameif management
security-level 100
ip address dhcp setroute
no shut
!
same-security-traffic permit inter-interface
same-security-traffic permit intra-interface
!
crypto key generate rsa modulus 2048
http server enable
http 0.0.0.0 0.0.0.0 management
ssh 0 0 management
ssh timeout 30
username admin nopassword privilege 15
username admin attributes
username cisco password cisco privilege 15
enable password cisco
aaa authentication ssh console LOCAL
aaa authentication http console LOCAL
service-type admin 

This way we will be able to connect to ASAv instance via ssh/http using local accounts.

26 Jan

Apple App Transport Security (ATS) and ASA self-signed SSL certificate

Apple care about users privacy and security quite well. Of course it’s a matter of opinion but Apple put strong focus on encryption and peer authentication. In 2015 Apple introduced App Transport Security (ATS) as part of their Network Framework With every release they are putting more and more responsibility on developers and content operators to provide proper traffic encryption proper certificate signing and chain etc. That means if application is trying to connect to HTTP server that does not support latest TLSv1.2 connection should fail.

There is no doubt that ATS is good for end users and that’s right direction every corporation should follow. But switching to TLSv1.2 is not something that can be done just like that, obtaining signed certificate expensive option, especially for development environments or if you are writing apps to just test something or for fun. Self-signed certificates are the solution for such cases but there are few problems that we can encounter.

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03 Jan

Cisco ASA REST API – Part III: Checking if prefix is directly connected

First published: 03/Jan/2017
Last update: 03/Jan/2017

It’s time to do some programming and really use REST API for something good. The first script will be used to check if specified prefix is directly connected to any of firewall interfaces. Script requires two arguiments: checked IP address and IP address of firewall. The execution of script will be as below


$ ./IfDirectlyConnected.pl
Usage: IfDirectlyConnected.pl [Checked IP Address] [Firewall Management IP]

At this demo script require IP addresses to be used and is not checking if arguments are IP addresses, just simply validating if two it’s executed with two arguments.

Please take a moment to look back to my post Cisco ASA REST API – Lab topology and programming language where I explained the topology of simulated network and presented IP addresses assigned to each device. Routing is configured and all subnets are reachable.

We will test te script on asav-1 firewall. The expected results are as follow:


$ ./IfDirectlyConnected.pl 10.0.12.5 172.16.1.51
Checking address 10.0.12.5 on firewall 172.16.1.51
RESULT: Destination route is directly connected

$ ./IfDirectlyConnected.pl 10.0.24.5 172.16.1.51
Checking address 10.0.24.5 on firewall 172.16.1.51
RESULT: Route in routing table but not directly connected

$ ./IfDirectlyConnected.pl 10.0.99.5 172.16.1.51
Checking address 10.0.99.5 on firewall 172.16.1.51
RESULT: Subnet not in routing table

Script is available on my GitHub

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24 Oct

Cisco ASA REST API – Part I: Getting started

First published: 24/Oct/2016
Last update: 31/Oct/2016
ASA REST API version: 1.3.2

REST is an acronym of Representational State Transfer (REST) API. This API provide administrators an option to perform CRUD operations which is Create, Read, Update, Delete. It fully rely on HTTPS as transport protocol and requires programming skills from administrators. But if you gain some experience its a good way of learning and getting familiar with whole new world when you more program devices than configure it.

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