This blog was selected as a finalist in Cisco BLOG Awards in the Best Analysis category, the category for resources that provide insightful discussions and help for networking architects around the world.
Fancy right? Do you agree? Go and vote, hit the big green button it’s the second one on the list 😉
The fancy way of configuring Cisco ACI Fabric is by using Python script for generating API calls. Those API calls are then used to configure Cisco ACI by pushing those calls to APIC controller using POSTMAN (or similar tool). Configuration changes done this way are those that you are doing often and without much chance of making mistakes.
You write a Python script and that script will take your configuration variables and generate API call that will configure the system quickly and correctly every time.
The thing is that you need to take the API call example and use Python to write a script that will recreate that API calls with your variables of configuration and do that correctly. You need to know to code in Python and you will need a certain amount of time to write that script.
If you are configuring Cisco ACI datacenter fabric it will sooner or later get to the point that you need to configure multiple objects inside the GUI which will, by using the click-n-click method, take a huge amount of time.
While using POSTMAN to create multiple objects of the same type is the preferred method that everybody is speaking about (because you can generate REST API calls using Python or something similar), the quickest way to do it is using POST of JSON configuration file directly through the GUI.
As described above, the POST of JSON for some simple yet repetitive configuration is the way to go. Let’s see how it’s done:
Creating multiple BDs inside a tenant in Cisco ACI:
If you check Juniper configuration guide for SRX firewall clustering, there will be a default example of redundancy-group weight values which are fine if you have one Uplink towards outside and multiple inside interfaces on that firewall.
set chassis cluster redundancy-group 0 node 0 priority 100 set chassis cluster redundancy-group 0 node 1 priority 1 set chassis cluster redundancy-group 1 node 0 priority 100 set chassis cluster redundancy-group 1 node 1 priority 1 set chassis cluster redundancy-group 1 interface-monitor ge-0/0/5 weight 255 set chassis cluster redundancy-group 1 interface-monitor ge-0/0/4 weight 255 set chassis cluster redundancy-group 1 interface-monitor ge-5/0/5 weight 255 set chassis cluster redundancy-group 1 interface-monitor ge-5/0/4 weight 255
This is the one: https://www.juniper.net/documentation/en_US/junos/topics/topic-map/security-chassis-cluster-verification.html
If you get to a situation where you may have multiple outside interfaces which are giving you Internet access or WAN access redundancy then maybe you don’t want failover to secondary SRX box to occur when you lose one of those two uplinks. If that’s the case, you should follow this article and get your SRX cluster to behave as it should.
This article describes the simplest way to enable MACSec using preconfigured static key-string. The example was tried on Catalyst 3850 and should work on other switches too.
There is another article that I wrote years ago which describes a more complex implementation with dot1x etc.
Media Access Control Security is the way to secure point-to-point Ethernet links by implementing data integrity check and encryption of Ethernet frame.
When you configure MACsec on a switch interface (and of course, on the other switch connected to that interface), all traffic going through the link is secured using data integrity checks and encryption.
Data integrity is done by appending 8-byte header and a 16-byte trailer to the Ethernet packet which is generated before a data is sent and checked upon receiving on the other switch to prove that the data inside the frame was not modified on the way. If the check fails, the packet gets dropped.
Sometimes you will have some L2 domains (Bridge Domains – BD) in your datacenter that will be used with hardware appliances like F5 NLB or something like an additional firewall, WAF or something similar. That is the case where ACI will not route or bridge but the only L3 point of exit from that kind of segment would be on actual hardware appliance outside ACI Fabric – connected to the Leaf port.
We will take an example here and use it throughout the article where BIG IP F5 NLB is used as an L3 termination of L2 BD 10.10.10.0/24.
F5 is directly connected to ACI Leaf and routing from 10.10.10.0/24 subnet (L2 BD) is done directly on F5 device which is default gateway for that subnet endpoints.
In those cases for some particular implementations when you decide not to use PBR or Service graphs, it will happen that appliances like our F5 would become L3 termination for some ACI L2 BD like the 10.10.10.0/24 from my beautiful image above.
You actually need three APIC controller servers to get the cluster up and running in complete and redundant ACI system. You can actually work with only two APICs and you will still have a cluster quorum and will be able to change ACI Fabric configuration.
In the MultiPod, those three controllers need to be distributed so that one of them is placed in the secondary site. The idea is that you still have a chance to keep your configuration on one remaining APIC while losing completely primary site with two APICs. On the other hand, if you lose secondary site, two APICs in the first site will still enable you to do configuration and management of ACI Fabric as nothing happened.
The second type of MultiPod fail is when you lose DCI (datacenter interconnect). In that case, both sites will keep working but will alert that the other side is down. The secondary site with one APIC will be in read-only mode and the primary site will be fully functional with two remaining APICs on that site. If some changes are made on the primary site, those changes will be replicated to the third controller on the secondary site when DCI recovers and configuration relating site B POD will be then pushed to POD 2 fabric.
DCI issues are not a good time for APIC replacement, just wait for DCI to start working normally and continue to use ACI APIC controllers as before the issues. You will still have the option to manage primary site if DCI fails and after DCI starts working again changes will be replicated to secondary site APICs and Fabric.
Please note that temporary DCI issues are not a good time to replace the APIC. If you are experiencing just a DCI outage the second site still works but it cannot be configured. Think about it, perhaps the best thing to do in this case is not to change the configuration of your fabric on either side while DCI doesn’t get back up and running. That way you are sure your configuration does not affect the MultiPod stability once DCI gets back up and sites start to communicate again.