• Category : Tech Tips

 
 

Carrying Label Information in BGP-4

Posted on March 19, 2018 by

Theory of BGP-LU Overview  MPLS typically has been used in core service provider (SP) networks. These deployments, however, have expanded beyond the network core and edge to the access and metropolitan networks. This rapid growth of edge-to-edge, label-switched paths (LSPs) across many networks  has presented scaling challenges.  In particular, emerging business demands related to Carrier Supporting Carrier (CSC), global growth of IPv6 traffic, and delivery of services over native IPv4 networks require pertinent and flexible solutions. Many organizations prefer to continue with the existing MPLS-based solutions to more recent overlay technologies such as VXLAN.   A solution that solves these potential...
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Arista Custom Event Handler To Take Action Based On Interface Utilization

Posted on October 12, 2018 by

Introduction An EOS event handler executes a Linux Bash shell command in response to a specific system event. An event handler consists of a Bash command, a trigger and a delay; when the trigger event occurs, the action is scheduled to run after a delay in seconds. With the particular customer, I was working with they wanted to shut down a mirror session when a bandwidth threshold was reached. The main reason for the custom event-handler was because they were heavily oversubscribing a mirror session destination and were worried about affecting their production traffic. In the scenario, they had several...
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Network CI/CD Part 3 – Building a network CI pipeline with Gitlab, Ansible, cEOS, Robot Framework and Batfish

Posted on October 3, 2018 by

Previously on Network CI/CD… We’ve kicked off this series with an overview of cEOS-lab and different container orchestration tools that can be used for network simulations. In the second post we’ve seen how to automate network verification and testing with Arista’s Robot framework library. In this final post, we’ll put it all together to demonstrate a simple data centre network CI pipeline that will run through a sequence of stages to build and test every new configuration change. Introduction Let’s take a typical data centre leaf-spine network as an example and let’s assume that Leaf-1/2 and Spine-1/2 are already built...
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How to Automate MAC Address Lookups

Posted on August 23, 2018 by

Introduction MAC addresses are often overlooked, compared to higher layers of the OSI model, but they are a necessity in the transfer of data across the network. MAC addresses are unique in nature, with the vendor OUI portion of the MAC, and the client portion of the MAC. There are many reasons why locating a device is necessary, a few of them are: A device is causing adverse affects to the network and the port needs to be shutdown A port needs to be re-configured for a new device, but it is not known where the device is connected to...
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Provisioning Cloud Vision Portal on AWS

Posted on August 21, 2018 by

Introduction This article demonstrates provisioning CloudVision Portal on AWS. With the release of CVP version 2018.x and upgrade of CVP platform to CentoOS 7.4, Cloud Vision Portal can be installed on CentOs servers with an RPM based script. This article specifically covers provisioning of CVP on the AWS EC2 Cloud platform. With CVP running on AWS users can easily manage AWS/OnPrem EOS instances from AWS and run analysis on CVP Telemetry/Compliance information with other AWS services and tools. Pre-Requisites 1) AWS account with appropriate privileges to create and access EC2 instances, DNS and NTP services. 2) Access to Arista.com Software...
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Arista Any Cloud Platform – vEOS Router in Azure Deployment Guide

Posted on August 20, 2018 by

Introduction In this document, we will demonstrate the deployment of Arista’s vEOS Router in Microsoft Azure. A vEOS Router can be leveraged to implement various Azure architectures such as the transit-edge or hub-spoke architecture. This particular document provides a step-by-step guide to deploy vEOS Router in a transit-edge architecture in the Azure public cloud. Overview Arista’s private and public cloud infrastructure both offer significant efficiencies that make it a compelling option for workload placement.   We have proven this in the private cloud with a simple yet scalable Spine/Leaf topology utilizing industry standard protocols across all of Arista switches. With...
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DHCP Snooping

Posted on August 16, 2018 by

Introduction EOS supports DHCP Relay feature, which relays DHCP Requests/Responses between DHCP clients and DHCP servers in different subnets. However, DHCP server does not have visibility of where the request originated from and can only make IP address allocation decisions based on the client MAC address alone (client MAC address is included in the DHCP packet as part of the payload). To remedy that, DHCP Option-82 was formalized to allow relay agent to include Remote ID and Circuit ID so that DHCP server can apply more intelligent allocation policy. Switch intercepts DHCP requests from client and insert Option-82 information in...
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DHCP Smart Relay

Posted on August 14, 2018 by

Introduction EOS DHCP relay agent forwards all the DHCP requests from the clients using the primary IP address of the interface as the ‘giaddr’ in the relayed/forwarded requests even when there are secondary IP addresses configured on the interface and there are multiple IP address pools from secondary IP subnets with available addresses on the server. DHCP smart relay feature supports forwarding requests with secondary IP addresses in the gateway address ‘giaddr’ field. This allows the DHCP server offer addresses to client requests with gateway addresses from secondary IP subnets configured on the interface. The smart relay agent keeps track...
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DHCP Relay

Posted on August 14, 2018 by

Introduction DHCP Relay feature forwards DHCP packets between client and server when DHCP server is not in the same broadcast domain as client. DHCP Relay should be configured on the gateway interface (SVI/ L3 interface ) for the clients. DHCP Relay agent creates a new unicast DHCP packet and sets the giaddr field to the ‘primary’ IP address of the interface on which DHCP request packet is received. The modified request packet is then relayed to one or more configured DHCP servers. DHCP server assigns ip address to client from the pool corresponding to giaddr field. Platform Compatibility Supported on...
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EVPN VXLAN Design Guide

Posted on August 6, 2018 by

EVPN VXLAN Design Guide   A Detailed Overview of the EVPN & VxLAN Protocols, Route Types, Use-Cases and Architectures   1. Introduction This document describes the operation and configuration of BGP EVPN Services over a VXLAN (Virtual eXtensible LAN) overlay on Arista platforms. The focus in this design guide is VxLAN as the protocol for the data-plane encapsulation for the overlay tunnels, and the functionality of the Multiprotocol BGP (MP-BGP) EVPN address-family for control plane signaling in the overlay.  MP-BGP EVPN is not only used for advertising MAC addresses, MAC and IP bindings and IP prefixes across the overlay; it...
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Arista Layer 2 VTEP EVPN VxLAN Route Type-1 Support

Posted on August 6, 2018 by

Arista Layer 2 VTEP EVPN Route Type-1 Support   Arista Layer 2 EVPN VTEP Inter-Operation With A/A Multi-homed Third-Party Layer 3 EVPN VXLAN VTEPs   Introduction   This document will explain the configurations required to support inter-working with EVPN VXLAN A/A multi-homed VTEPs, also known as L2 ECMP in VxLAN EVPN.   Currently, EOS uses MLAG is used to achieve Multi-homing in EVPN VxLAN Topologies, with an any-cast VxLAN VTEP configured on the MLAG pair, and as such does not need to support EVPN Multihoming Tx (Type-1 route generation). EOS can however install received Type-1 routes and can...
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Multi-Tenant EVPN VXLAN IRB Configuration & Verification Guide (iBGP Overlay eBGP Underlay)

Posted on August 6, 2018 by

Multi-Tenant EVPN VXLAN IRB Configuration & Verification Guide   Symmetric and Asymmetric IRB With VLAN Based and VLAN Aware Bundle Services Using an iBGP Overlay and eBGP Underlay Topology Logical Diagrams Tenant-A: Symmetric IRB Tenant-B: Asymmetric IRB Platform Support: https://www.arista.com/en/support/product-documentation/supported-features Topology Overview   In the symmetric and asymmetric IRB setups illustrated in the figures above;  for tenant-a four subnets are stretched across the two MLAG domains; with two subnets (vlan 10 – 10.10.10.0/24 and vlan 11 – 10.10.11.0/24) configured as a VLAN based service, and two other subnets (vlan 12 – 10.10.12.0/24 and vlan 13 – 10.10.13.0/24) as a vlan-aware...
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How to Minimize Impact when Port is Flapping

Posted on July 20, 2018 by

Intro A flapping port can cause network instability and disruption as L2/L3 protocols are constantly forced to re-converge and rebuild the topology with every port status change. If flapping happens at short intervals, it can cause a spike in the CPU utilization as well.  To minimize the impact in such scenarios, Arista introduced the ‘link-debounce’ feature. The idea is to wait until the port status is stable for a period of time before L2/L3 protocols are notified about the status change (up/down).  Feature Description The link-debounce command configures the link debounce under network interfaces. Link debounce time is the time...
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CVP REST API Tricks. Part 1: Form Builder with Dynamic Fields

Posted on June 29, 2018 by

Introduction Arista CloudVision Portal (CVP) covers customer demand for automation, provisioning and monitoring (telemetry) in a very simple and efficient way. Nevertheless, sometimes customers can have certain requests that are not covered by the default CVP workflow. Fortunately CVP workflow can be easily customised with REST API. “CVP REST API Tricks” series will cover some examples that are not part of the default feature set, but can be easily implemented via REST API.  WARNING: Examples covered by “CVP REST API Tricks” deviate from the default CVP provisioning model. If you are going to use that in production, be sure that...
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Cloud Tracer + Telemetry

Posted on June 26, 2018 by

Arista’s Cloud Tracer, coupled with CloudVision telemetry integrate together to create a compelling visibility and troubleshooting solution. Cloud Tracer Cloud Tracer is a feature within EOS software that monitors the performance of resources in the network.   Traditionally, network-based performance probes were based on proprietary packet formats and limited to router-router measurements.  Cloud Tracer is able to track and measure performance against an HTTP or HTTPS URL and provide measurements for response time, packet loss, round-trip latency, and jitter.  The URL could be another network device or a critical application resource. CloudVision Telemetry Arista’s CloudVision telemetry is a robust, state streaming...
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40G TapAgg BiDi Design

Posted on June 18, 2018 by

Arista QSFP BiDi optics allow both transmit and receive signals, to travel on the same fiber slice. The QSFP BiDi design provides 40Gbps (20Gbps egress & 20Gbps ingress on each fiber slice) bandwidth using the duplex MMF (OM3, & OM4) cable. This way one can leverage the existing cabling infrastructure to upgrade BW from 10Gbps to 40Gbps ( see diagram 1). The BiDi optics provides a number of benefits and some are listed below: ▪   Fiber replacement not required when moving from 10Gbps to 40Gbps ▪   Lower CAPEX as 75% less fiber comparing parallel cable (40G SR4) ▪   Interoperable with Industry standard...
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Robot Framework for Auto Test

Posted on June 14, 2018 by

Introduction In-house EOS code certification is generally a time consuming process as it involves a lengthy life cycle. At a high-level, the various stages involved are: Setting up the test environment Designing test cases Executing test cases Documenting test results Validating gathered test results As you can imagine, stages 3, 4 and 5 can be the most time consuming as they warrant an error-free execution. Additionally, since image and configuration management would be simplified, most customers would like to have a single EOS version deployed across all their platforms and networks. So certifying code at a brisk pace, on all platforms,...
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Understanding Logging Levels

Posted on June 6, 2018 by

Overview   EOS generates a number of logs to notify various events such as interface going down,spanning-tree state change, agent restart, bgp neighborship flap etc. One event can be more impacting than other and thus it is necessary that respective logs reflect that severity. This is why all the logs are categorized into different severity/logging levels. There are 8 logging levels available, from 0-7, 0 being most critical and 7 being least critical.  alerts         Immediate action needed           (severity=1)  critical       Critical conditions              (severity=2)  debugging      Debugging messages                (severity=7)  emergencies    System is unusable                (severity=0)  errors         Error conditions                  (severity=3)  informational  Informational messages            (severity=6)  notifications...
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ZTPv6 using DHCPv6 Relay Agent

Posted on June 2, 2018 by

1. IntroductionZTP (v4/v6) is a simple hands-off approach to both initial set up and upgrading an existing network.  ZTP does not require entering into the switch CLI, speeds up and simplifies deployment, reduces the risk of human error, and can adapt to many deployment scenarios. It offers scripting extensibility for complex networks and flexible provisioning using standard tools.  Additionally, the switch can be ZTP booted using a variety of identifiers, such as its MAC address, serial number, or LLDP neighbors. Arista switch’s ZTP process starts with communicating to a DHCP(v4/v6) Server, where apart from getting the IP Address, Default Gateway,...
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Tap Aggregration Tip: Popping MPLS tags for Untagged or VLAN based Tools

Posted on May 12, 2018 by

In Tap Aggregation scenarios common in WAN and Service Provider environments, MPLS tags are present.  Many of the analysis tools do not understand these tags and so the Arista DANZ feature set allows for these to be removed.  This functionality has been around since 4.15.0F however initially had the limitation that the traffic would always be sent out the Tool port with a VLAN tag.  However, some tools not only do not understand MPLS, but also VLAN tags, so this tip describes how to deal with both 802.1q and untagged scenarios. Step 1:  Configure MPLS pop/strip on the Tap port:...
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Integrating Salt and Arista ZTP Server for Zero Touch Automation of EOS

Posted on May 7, 2018 by

Zero Touch Provisioning The term ZTP or Zero Touch Provisioning is a feature often heard, which EOS has offered since the early days. During the initial boot, if a startup-configuration file is not found in the /mnt/flash/startup-configuration directory, the EOS device will automatically boot into ZTP mode. The switch will obtain an IP address from a DHCP server including DHCP options 66 and 67. Next the switch will ask the ZTP server or a server designated within option 66/67  for a bootstrap file. In this post we will use the Arista ZTP server which can be found here.  This process is depicted in the following picture: The...
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