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This article shows how to perform an ISSU (In-Service Software Upgrade) on a Nexus Data Center switch (7000 and 7700 models) and avoid service and network disruption. We explain the importance of keeping your NX-OS software updated, how the upgrade process is executed, explain the purpose of the Kickstart and System images, provide methods on how to transfer the NX-OS images to the switch bootflash on both supervisor engines, verify ISSU capability and test/simulate the upgrade process.
In addition we cover useful commands to discover issues that might occur during the upgrade process, configuration backup methods, upgrading a Nexus 7000 and Nexus 7700 series with single or dual Supervisor Engines (SUP1 and SUP2 models).
Here is a quick overview of what’s covered:
Upgrading your NX-OS can be a daunting task as there is always the risk something might go wrong. Despite this, it is very important to ensure your core Nexus switch is running one of the latest and supported images.
If you’re looking for reasons why to take the risk and upgrade, here are a few that might help convince:
It’s always recommended to perform a thorough research of the NX-OS version under consideration to identify caveats or issues that might affect your production environment. This information can be found on Cisco’s website or by opening a Cisco TAC Service Request.
The ISSU upgrade process provides us with the ability to upgrade a Nexus 7000/7700 switch without network or service disruption. During the ISSU process all Nexus modules and Supervisor Engines are fully upgraded without requiring a switch reboot.
Firewall.cx has covered Colasoft Capsa several times in the past, but its constant improvements make it well worth revisiting. Since the last review, the version has bumped from 7.6.1 to 11.1.2+, keeping a similar interface but scoring plenty of new features. In fact, its change is significant enough to warrant a full re-evaluation rather than a simple comparison.
For the unfamiliar, Colasoft Capsa Enterprise is a widely respected network protocol analyzer that goes far beyond free packet sniffers like Wireshark. It gives users detailed information about packets, conversations, protocols, and more, while also tying in diagnosis and security tools to assess network health. It was named as a visionary in Gartner’s Magic Quadrant for Network Performance Monitoring and Diagnostics in 2018, which gives an idea of its power. Essentially, it’s a catch-all for professionals who want a deeper understanding of their network.
The installation of Capsa Enterprise is a clear merit, requiring little to no additional configuration. The installer comes in at 84 MB, a very reasonable size that will be quick to download on most connections. From there, it’s a simple case of pressing Next a few times.
However, Colasoft does give additional options during the process. There’s the standard ability to choose the location of the install, but also choices of a Full, Compact, or Custom install. It lets users remove parts of the network toolset as required to reduce clutter or any other issues. Naturally, Firewall.cx is looking at the full capabilities for the purpose of this review.
The entire process takes only a few minutes, with Capsa automatically installing the necessary drivers. Capsa does prompt a restart after completion, though it can be accessed before then to register a serial number. The software offers both an online option for product registration and an offline process that makes use of a license file. It’s a nice touch that should appease the small percentage of users without a connection.
After starting Capsa Enterprise for the first time, users are presented with a dashboard that lets them choose a network adapter, select an analysis profile, or load packet files for replay. Selecting an adapter reveals a graph of network usage over time to make it easier to discern the right one. A table above reveals the speed, number of packets sent, utilization, and IP address to make that process even easier.
However, it’s after pressing the Start button that things get interesting. As data collection begins, Capsa starts to display it in a digestible way, revealing live graphs with global utilization, total traffic, top IP addresses, and top application protocols.
This article provides in-depth analysis of DHCP Option 82 (DHCP Relay Agent) which is one of the +180 DHCP Options available to the DHCP protocol and used by the Bootstrap Protocol (BOOTP) used for allowing diskless client machines to discover and obtain their IP address. We’ll show you how DHCP Option 82 is used when implementing DHCP Snooping, the structure and content of DHCP Option 82, how and where it’s injected and removed from DHCP messages plus much more. You’ll can also download our DHCP/BOOTP Options Excel file and Wireshark packet captures of DHCP packets with Option 82 used in this article to help further understand all topics covered.
Let’s take a look at the list of topics covered in this article:
It’s highly recommend to read through our DHCP Snooping – DHCP Attack Mitigation article which is a foundation article.
The DHCP Options field is included inside every DHCP packet and is critical for the correct operation of the DHCP/BOOTP protocol. You’d be surprised to know that there are almost 200 different DHCP Options available and there are more added as new features are introduced in the protocol.
The material used in this article such as wireshark DHCP Options 82 packet captures and DHCP/BOOTP Options excel file are freely available to download from our Article Attachments section.
The diagram below shows the structure of a DHCP packet and highlights the position of the DHCP Options field.
It is important to understand that the above DHCP packet is the data payload within an Ethernet frame using UDP as the transport protocol.
The below screenshot was taken from a packet analyzer and shows an Ethernet frame with the DHCP data payload expanded:
We’ve highlighted sections of the DHCP protocol using the same colours as our previous diagram to help the correlation process. Every field shown in our diagram maps directly to the fields of the captured DHCP packet.
The area marked in green is the section where the DHCP Options field is located. In our captured packet there are a total of 8 DHCP Options used, among them is also Option 82 (Agent Information Option).
The DHCP Option 82, aka Agent Relay Information Option or Agent Information Option, was originally created by RFC 3046 to allow the DHCP relay agent (e.g switch, router, firewall or server) to identify itself and the DHCP client that sent the original DHCP message.
The DHCP Option 82 is inserted and removed by the DHCP Agent Relay (e.g switch) as shown in the diagram below:
While some DHCP servers might not support the Option 82 they are still required to copy the Option 82 value received from the DHCP client and include it in all replies back to the client. We’ll discuss the Option 82 insertion and removal process in the next section.
As we saw earlier, the DHCP Options field is positioned at the end of the DHCP packet and always contains multiple DHCP options. This of course means the DHCP Option field varies in length according to the number of options used:
In the rush to keep pace with the many challenges facing today’s organizations, all too often networking teams end up adopting practices and processes that are, shall we say, less than perfect. You probably have seen a few yourself in your own organization.
Management refusing to consider new vendors because, well, they’re new. Engineers wanting to do everything manually when automation would save them a ton of time. Overspending on capacity when there are more affordable alternatives. You get the picture.
Some practices are well known, others are less obvious. A great starting point for identifying the worst of the worst in your organization was a recent list compiled by Gartner. The list culls insight from several thousand client interactions. While the Gartner report requires payment, a free eBook from Cato Networks explains each networking practice and how they can be addressed with a cloud-based SD-WAN.
The practices fall into three categories — cultural, design and operational, and financial:
We have some exciting news for you today!
Altaro has launched a great contest in celebration of SysAdmin Day on 27th July 2018!
They will be giving away Amazon eGift Cards to the first 100 eligible entries and 1 Grand Prize to 1 lucky winner.
The Grand Prize winner will be able to choose any prize from the following: a PlayStation 4 Pro, Xbox One X, a 3-year membership of Amazon Prime, an Unlimited Plus Edition of Altaro VM Backup, and more!
All contest participants will even get FOREVER FREE backup for 2 VMs when they download Altaro VM Backup!
Want to WIN?
Here’s what you need to do to:
Good luck!