Thursday, August 28, 2014

Convergence between SVI vs Routed Interface - Cisco 3548 NXOS

Convergence of SVI vs. Routed link on a Cisco 3548 Nexus running A1.1c

Link failures were simulated by “shut” on the remote interface.


 2014 Aug 28 10:04:06.348524 switch %ETHPORT-5-IF_DOWN_LINK_FAILURE: Interface Ethernet1/9 is down (Link failure)  
 2014 Aug 28 10:04:06.478105 urib: "direct": no more next hops  
 2014 Aug 28 10:04:06.478419 urib: Deleting & Freeing  
 2014 Aug 28 10:04:06.479344 urib: "local": no more next hops  
 2014 Aug 28 10:04:06.479618 urib: Deleting & Freeing  
 2014 Aug 28 10:04:06.479954 urib: "broadcast": no more next hops  
 2014 Aug 28 10:04:06.480215 urib: Deleting & Freeing  
 2014 Aug 28 10:04:06.480542 urib: "broadcast": no more next hops  
 2014 Aug 28 10:04:06.480951 urib: Deleting & Freeing  
 2014 Aug 28 10:04:06.696703 urib: "am": no more next hops  
 2014 Aug 28 10:04:06.697117 urib: Deleting & Freeing  

Route deletion = 478419 – 348524 =  129895us

Wednesday, August 27, 2014

Configuring Arista - VARP aka Virtual ARP

Traditional FHRP (First Hop Redundancy Protocol) such as VRRP or HSRP allows only one gateway to forward at any given point in time. There is an 'Active' forwarder while the other forwarder stays in standby mode monitoring and only to become 'Active' when there is a failure on the 'Active' node. VARP or Virtual ARP (Arista's proprietary) solves this issue elegantly by allowing all configured nodes to be forwarding traffic rather the one of the node sitting idle. In this blogtorial we will configure and verify VARP and since there is not really much to the configuration, this 'how-to' should be a quick one. If you need a primer on FHRP such HSRP/VRRP/GLBP/IRDP please see my other blogtorials here.

Consider this topology with a traditional FHRP deployed such as VRRP.

Configuring Arista MLAG - Basic setup

Layer 2 All links forwarding none blocking ... Take that Spanning Tree!! (-- no offense Radia Perlman :) --) This is what you get with Arista's proprietary MLAG -- short for Multi-Chassis Link Aggregation. Although Spanning-Tree is extremely efficient at preventing loops and keeping your network healthy, it does come with a hefty price tag -- essentially blocking half of your uplinks. In this blogtorial, we will go through brief overview of spanning-tree and then deep dive into MLAG concepts, caveats, and configurations. As of this writing, MLAG is currently supported on Arista's 75xx, 7500E, 7048, 7150, 7050, 7050X, 7250X, and 7300X. If you are familiar with Cisco's proprietary vPC (Virtual Port-Channel) then most of this should be fairly straight forward.

Consider this traditional Layer 2 design where half of your links are blocked to prevent loops in the network.