Collection of useful, relevant or just fun places on the Internets for %dateend% and a bit commentary about what I've found interesting about them:
The post Internets of Interest – 27 July 2014 appeared first on EtherealMind.
Another day, another issue with an automation script. Today’s task was to grab the configuration file from an A10 Thunder load balancer. I don’t want to use the GUI, and while I could – in theory – use ssh and … Continue reading
If you liked this post, please do click through to the source at A10, aXAPI, and Another Awesome App and give me a share/like. Thank you!
In the last post, I introduced you to the concept of control plane abstraction, specifically the OpenFlow implementation. I talked about how OpenFlow allows us to specify the flows that we want to be programmed into the forwarding plane, from outside the forwarding device itself. We can also match on fields we typically don’t have access to in traditional networking, since current hardware is optimized for destination-based forwarding.
In this post, I plan to cover quite a few bases. The goal of this post is to address the main concepts of OpenFlow’s operation, with links to find out more. With this post, you’ll be armed with the knowledge of what OpenFlow does and doesn’t do, as well as resources to dive even deeper.
NOTICE: This blog post was written referencing the specification and implementations of OpenFlow 1.3 – since this version, some aspects of the protocol may have changed (though it is likely the fundamentals discussed here will be mostly the same)
The OpenFlow specification describes a wide variety of topics. For instance, the protocol format that’s used to communicate with an OpenFlow switch Continue reading
Is released by HP the new version of simulator for network devices (Switches and Routers) based on Comware 7 OS. This software is called HP Network Simulator.
I’m very happy about that because I have waited for a long time to run some commands and features in a lab environment.
The simulator is based on Cowmare 7 ( most commands are very similar to OS 5 version)
List below the link for download, inside there are some instructions for installing and configuring the topology that you wish.
Despite of the software working on GUI mode, the topology design must be made via text in a configuration file (also explained in the software manual).
Enjoy it, share and comment. It’s a good time to celebrate.
If the link is broken, please leave a comment.
Kirk Byers has been doing network automation work for quite a while now. I’ve been following his Pynet mailing list, where he teaches list members in a series of structured lessons how to code in Python, harnessing the scripting language’s power for network automation. I met Kirk at Cisco Live US, and we got to […]
The post Show 198 – Kirk Byers on Network Automation with Python & Ansible appeared first on Packet Pushers Podcast and was written by Ethan Banks.
In the last few posts on this topic, we’ve talked about the various bits and parts of the DNS system, from who pays to how it works to DNS tools. This time, we’re going to finish off DNS in this (probably record breaking for Packet Pushers) series, and talk about some various aspects of DNS […]
At some point, Network engineers will likely face some type of issue with MTU or maximum transmittable unit. Their first experience with this may be an eye opening and time consuming effort. After resolving the issue, those with a thirst for knowledge will take the necessary time to understand the issue.
MTU problems are most often seen when Path MTU Discovery, or PMTUD, fails to function. This is the process by which one end host determines the largest possible packet size to another station on the network. Symptoms of this type of issue include two devices having proven reachability, but applications fail to work in a way that indicates a network issue. Some applications may even crash or hang the system.
Symptoms of PMTUD Failure
To understand the problems of Path MTU Discovery, it is first necessary to understand how MTU relates to the conversation. MTU, or maximum transmittable unit, is the maximum chunk of data that a given interface can transmit. The type of data receiving our attention is IP Continue reading
A few weeks ago, I was working with the NX-API currently found on Cisco’s Nexus 9000 series switches, and ran into some peculiar behavior.
NX-API returns all information in terms of Tables and Rows. For a specific example, let’s look at what NX-API returns when I ask the switch for running OSPF processes:
There’s actually a lot more information in this snippet that pertains to the OSPF process itself, but I have omitted it for brevity. This specific example focuses on the section that describes the areas in this OSPF process.
{
"ins_api": {
"sid": "eoc",
"type": "cli_show",
"version": "0.1",
"outputs": {
"output": {
"code": "200",
"msg": "Success",
"input": "show ip ospf",
"body": {
"TABLE_ctx": {
"ROW_ctx": {
### OSPF process information omitted for brevity ###
"TABLE_area": {
"ROW_area": {
"age": "P15DT15H27M6S",
"loopback_intf": "1",
"passive_intf": "0",
"last_spf_run_time": "PT0S",
"spf_runs": "9",
"lsa_cnt": "5",
"no_summary": "false",
"backbone_active": "true",
"stub": "false",
"aname": "0.0.0.0",
"total_intf": "2",
"auth_type": "none",
"act_intf": "2",
"nssa": "false",
"lsa_crc": "0x18d91"
}
}
}
}
}
}
}
}
}
NXAPI uses a special tag that starts with TABLE, and within that, tag(s) that start with ROW, whenever it needs to describe something that would normally be Continue reading
In my last post, we wrapped up the base components required to deploy NSX. In this post, we’re going to configure some logical routing and switching. I’m specifically referring to this as ‘logical’ since we are only going to deal with VM to VM traffic in this post. NSX allows you to logically connect VMs at either layer 2 or layer 3. So let’s look at our lab diagram…
If you recall, we had just finished creating the transport zones at the end of the last post. The next step is to provision logical switches. Since we want to test layer 2 and layer 3 connectivity, we’re going to provision NSX in two separate fashions. The first method will be using the logical distributed router functionality of NSX. In this method, tenant 1 will have two logical switches. One for the app layer and one for the web layer. We will then use the logical distributed router to allow the VMs to route to one another. The 2nd method will be to have both the web and app VMs on the same logical layer 2 segment. We Continue reading
I’m always wondering if the addresses I’m assigning to interfaces aren’t already in DNS. So I came up with a little BASH script that takes a list of IP addresses and performs an nslookup on them to ensure they’re not in use already:
$nslookup < input-filename > output-filename
The addresses in the input file are carriage return delimited.
A better use for this would be to check if DNS entries already have an IP address assigned to them.
Having dual sites or multiple sites in Active/Active mode aims to offer elasticity of resources available everywhere in different locations, just as with a single logical data center. This solution brings as well the business continuity with disaster avoidance. This is achieved by manually or dynamically moving the applications and software framework where resources are available. When “hot”-moving virtual machines from one DC to another, there are some important requirements to take into consideration:
As with several other network and security services, the Continue reading
