# ARP Published articles for ARP. This is one page of public article previews, not the complete archive. Follow Next page to continue. Summaries are not the original full articles. ## Worth Reading 072826 DevFeed: [Worth Reading 072826]() Original publisher: [Read original article]() Author: Russ Published: 2026-07-28T10:59:47Z Content type: article Language: en Sources: [rule 11 reader]() Topics: [Internet](), [data](), [Internet Engineering Task Force (IETF)](), [Networks](), [5G](), [Machine learning]() Tags: [5g](), [ai](), [arp](), [article](), [data](), [ietf](), [internet](), [ipv6](), [networks](), [worth-reading]() ### AI overview A developer reading roundup covering Internet infrastructure, synchronization of replicated data, IPv6-only networking, IPv4 dependencies, ARP, an IETF proposal, 5G control-plane timers, modern machine-learning pipelines, and the integration of AI into everyday applications. ### Source excerpt Today's Internet runs on a vast infrastructure of replicated data, and the difference between order and chaos lies in maintaining consistency through synchronization across the many distributed points where that data is published. IPv6-only networks often still depend on IPv4 subnets and ARP. This article introduces an IETF proposal to eliminate both. Traditional software engineering approaches reliability as a binary state of uptime and downtime. Modern ML pipelines render this paradigm obsolete. Yet while the radios and protocols largely reuse terrestrial 5G designs, one small but crucial component has been left behind: The control plane timers that quietly govern how registration, mobility, and session procedures behave under real-world conditions. Apparently, nearly all of them have reached the same conclusion. I don't merely need AI occasionally. I need it waiting inside every search bar, messaging app, music player, and document reader I already use. ## What's ARP Got to Do with It? DevFeed: [What's ARP Got to Do with It?]() Original publisher: [Read original article]() Author: Remco van Mook Published: 2026-07-23T06:35:41Z Content type: article Language: en Sources: [RIPE Labs]() Topics: [Internet](), [Network](), [Networks](), [FIRST]() Tags: [arp](), [article](), [enterprise](), [ietf](), [internet](), [internet-infrastructure](), [ipv4](), [network](), [networks]() ### AI overview The article examines why ARP still matters by distinguishing durable demand for IPv4 reachability from the local-network architecture traditionally used to provide it. It argues that many access and hosting segments isolate subscribers or tenants and use the local IPv4 subnet mainly as a mechanism for reaching the gateway, rather than for lateral communication. ### Source excerpt It's only ARP. It works. So how much can it really matter? The answer lies beyond ARP itself, in the IPv4 layer cake that grew around it over four decades. The IPv4 internet is not going away in bounded time, and nobody should pretend otherwise. ## Anycast-Only Gateways in EVPN Asymmetric IRB DevFeed: [Anycast-Only Gateways in EVPN Asymmetric IRB]() Original publisher: [Read original article]() Published: 2026-06-24T06:19:00Z Content type: article Language: en Sources: [ipSpace.net blog]() Topics: [evpn](), [VXLAN]() Tags: [arp](), [evpn](), [vxlan]() ### AI overview This article examines ARP resolution in EVPN asymmetric IRB environments where PE devices use only a shared anycast MAC/IP address. It describes how silent hosts can cause communication to stall because an ARP reply may be intercepted, and explains how Arista EOS accepts the unsolicited reply to create a MAC/IP route and complete forwarding. ### Source excerpt In the previous blog post, I described how ARP works in an EVPN asymmetric IRB environment where the PE devices share an anycast MAC/IP address in addition to a unicast MAC/IP address. Today, let's see how well things work if the PE devices have only the anycast MAC/IP address: Packet forwarding in an EVPN asymmetric IRB design using only anycast gateways Read more ... ## ARP with Anycast Gateways in EVPN Asymmetric IRB DevFeed: [ARP with Anycast Gateways in EVPN Asymmetric IRB]() Original publisher: [Read original article]() Published: 2026-06-17T06:19:00Z Content type: article Language: en Sources: [ipSpace.net blog]() Topics: [evpn](), [networking](), [Routing (disambiguation)](), [Protocol (disambiguation)](), [VXLAN]() Tags: [arp](), [evpn](), [routing](), [vxlan]() ### AI overview This article examines ARP behavior with anycast gateways in EVPN asymmetric IRB. It focuses on a topology where each PE has device-specific and shared MAC/IP addresses, and hosts use the shared anycast gateway. The article describes ARP requests, shared gateway MAC addresses, and gratuitous ARPs, including observations about Arista EOS. ### Source excerpt In previous blog posts, I described the ARP issues in EVPN environments, starting with centralized routing, and then asymmetric IRB with unicast (per-leaf-switch) first-hop gateways. Of course, no self-respecting vendor would tell you to do that; anycast gateways are all the rage these days. As always, anycast gateways could mean different things, depending on which vendor documentation you read ;) Active-active VRRP (one device is the active VRRP gateway, but all devices listen to the VRRP MAC address). Shared MAC+IP address beside device-specific unicast MAC and IP addresses. Shared MAC+IP address with no PE-specific IP address. Read more ... ## EVPN Centralized Routing with Arista EOS DevFeed: [EVPN Centralized Routing with Arista EOS]() Original publisher: [Read original article]() Published: 2026-06-03T05:44:00Z Content type: tutorial Language: en Sources: [ipSpace.net blog]() Topics: [evpn](), [Routing (disambiguation)](), [networking](), [VXLAN]() Tags: [arp](), [cache](), [evpn](), [implementation](), [netlab](), [route](), [router](), [routing](), [vxlan]() ### AI overview This article examines which EVPN routes Arista EOS generates in a centralized routing design where a spine switch acts as the router and leaf switches operate at Layer 2. It explains that the central router does not advertise MAC+IP routes for hosts attached to its VLANs, routers must perform their own ARP resolution, and minimal configuration can cause routed traffic to be flooded. ### Source excerpt A month ago, I described ARP issues in EVPN centralized routing design, and Naveen Kumar Devaraj was kind enough to add some Arista EOS implementation details. Today, let's explore what EVPN routes Arista EOS generates in that scenario. We'll use a very simple lab topology with a spine switch acting as a router. The leaf switches are layer-2 switches. Packet forwarding in centralized routing design Read more ... ## Lab: EVPN Asymmetric IRB with Anycast Gateways DevFeed: [Lab: EVPN Asymmetric IRB with Anycast Gateways]() Original publisher: [Read original article]() Published: 2026-05-15T05:52:00Z Content type: tutorial Language: en Sources: [ipSpace.net blog]() Topics: [evpn](), [VXLAN]() Tags: [arp](), [container](), [evpn](), [github](), [infrastructure](), [installation](), [mac](), [vxlan]() ### AI overview This lab exercise demonstrates EVPN asymmetric IRB with anycast gateways and addresses ARP issues. It requires extending VLANs into end-to-end MAC-VRF instances and adding IRB and anycast gateways. The lab can run on netlab-enabled infrastructure, a free GitHub Codespace, or an Apple-silicon Mac using an Arista cEOS container. ### Source excerpt I postponed the discussion of ARP issues with EVPN anycast gateways to keep yesterday's blog post reasonably short. If you're impatient and want to try that out, I have just the right lab exercise for you; you'll have to extend VLANs into end-to-end MAC-VRF instances and add IRB and anycast gateways: Explore the lab exercise You can run the lab on your own netlab-enabled infrastructure (more details), but also within a free GitHub Codespace or even on your Apple-silicon Mac (installation, using Arista cEOS container, using VXLAN/EVPN labs). ## ARP with EVPN Asymmetric IRB DevFeed: [ARP with EVPN Asymmetric IRB]() Original publisher: [Read original article]() Published: 2026-05-14T05:45:00Z Content type: tutorial Language: en Sources: [ipSpace.net blog]() Topics: [evpn](), [VXLAN](), [networking](), [BGP]() Tags: [arp](), [bgp](), [bridging](), [evpn](), [netlab](), [vxlan]() ### AI overview This tutorial explains ARP behavior in EVPN asymmetric Integrated Routing and Bridging (IRB). It identifies prerequisites for forwarding between VLANs, including creating ARP entries from MAC+IP routes and having end hosts send an early ARP request for their first-hop gateway. It also describes how to verify the behavior with a netlab topology and EVPN route and ARP-table inspection. ### Source excerpt In a previous blog post, I described the ARP issues you'll encounter when using centralized routing (on a spine switch) between two EVPN MAC-VRF instances (a fancy name for a VLAN encapsulated in VXLAN or MPLS). That blog post established a baseline that will help us unravel the ARP behavior in a more realistic scenario: asymmetric Integrated Routing and Bridging (IRB). That's a mouthful, but it's really quite a simple concept; the following diagram explains the asymmetric forwarding behavior: Packet forwarding in an EVPN asymmetric IRB design Read more ... ## ARP Issues in EVPN Centralized Routing Design DevFeed: [ARP Issues in EVPN Centralized Routing Design]() Original publisher: [Read original article]() Published: 2026-05-05T05:45:00Z Content type: article Language: en Sources: [ipSpace.net blog]() Topics: [evpn](), [networking](), [IP routing](), [Routing (disambiguation)]() Tags: [arp](), [ethernet](), [evpn](), [ip-routing](), [routing]() ### AI overview This article examines ARP and traffic-flooding problems in a centralized routing design using EVPN MAC-VRFs. It explains the expected packet flow through a spine switch and describes how implementations that do not advertise VLAN IP/MAC addresses can prevent switches from locating the gateway MAC, causing inter-subnet traffic to be flooded. ### Source excerpt Adding IRB to a EVPN MAC-VRFs (the fancy way of saying stretched VLANs) seems like a no-brainer: Add IP addresses to VLAN interfaces Optionally add a shared anycast gateway Declare "Mission Accomplished" (and try to ignore the inevitable phone call at 2 AM on a Sunday night) Making that work in a multi-vendor environment is even more fun1, as I sadly discovered when creating the EVPN lab exercises or trying to figure out why some EVPN implementations were failing netlab EVPN integration tests. Read more ... ## On Generating EVPN MAC/IP Routes DevFeed: [On Generating EVPN MAC/IP Routes]() Original publisher: [Read original article]() Published: 2026-04-29T05:38:00Z Content type: opinion Language: en Sources: [ipSpace.net blog]() Topics: [evpn](), [BGP](), [networking]() Tags: [arp](), [bgp](), [evpn](), [ip](), [mac]() ### AI overview The article explains that Arista EOS generates separate EVPN MAC-only and MAC+IP routes. MAC table updates trigger MAC-only routes, while ARP table updates trigger MAC+IP routes, which can increase the size of the EVPN BGP table. ### Source excerpt Naveen Kumar Devaraj was reading my Integrated Routing and Bridging (IRB) with EVPN MAC-VRF Instances lab exercise and spotted this detail: Arista EOS originates MAC-IP routes with and without IP addresses, effectively doubling the size of the EVPN BGP table He kindly wrote a LinkedIn comment explaining that behavior: Read more ... ## Finding End-to-End Paths: Topology and Endpoints DevFeed: [Finding End-to-End Paths: Topology and Endpoints]() Original publisher: [Read original article]() Published: 2025-06-06T05:51:00Z Content type: tutorial Language: en Sources: [ipSpace.net blog]() Topics: [networking](), [Routing (disambiguation)](), [Network design]() Tags: [arp](), [bridging](), [dhcp](), [discovery](), [ipv4](), [ipv6](), [network](), [networking-fundamentals](), [router](), [routing]() ### AI overview This article explains how networks discover topology and endpoints, build forwarding tables, and adapt end-to-end paths when links or nodes fail. It contrasts complete topology views in link-state protocols with local-neighbor knowledge in distance-vector protocols, and describes learning mechanisms including bridging, ARP, DHCP, and ICMPv6 Neighbor Discovery. ### Source excerpt We know there are three main ways to move packets across a network. However, before we can start forwarding packets, someone has to populate the forwarding tables in the intermediate devices or build the sequence of nodes to traverse in source routing. Usually, whoever is responsible for the contents of the forwarding tables must first discover the network topology. Let's start there, using the following network diagram to illustrate the discussion. Read more ... ## How Linux ARP Behavior Can Break Static-Route Tests with Multiple Next Hops DevFeed: [How Linux ARP Behavior Can Break Static-Route Tests with Multiple Next Hops]() Original publisher: [Read original article]() Published: 2025-04-22T05:55:00Z Content type: article Language: en Sources: [ipSpace.net blog]() Topics: [Linux](), [Network](), [Ethernet]() Tags: [arp](), [ethernet](), [experiment](), [linux](), [netlab](), [network](), [route](), [tests](), [validation]() ### AI overview The article investigates a netlab integration-test failure involving static routes with two next hops. It finds that default ARP behavior on a multi-subnet Linux host can cause Linux to send an ARP request using the IP address of another interface, while Junos does not answer it, causing the ping test to fail until the ARP cache is warmed. ### Source excerpt The amount of weird stuff we discover in netlab integration tests is astounding, or maybe I have a knack for looking into the wrong dark corners (my wife would definitely agree with that). Today's special: when having two next hops kills a static route. TL&DR: default ARP settings on a multi-subnet Linux host are less than optimal. We use these principles when creating netlab integration tests: They should contain a single device-under-test and a bunch of attached probes. They should test a single feature. They should not rely on the device-under-test. All validation has to be done on probes. How do you test static routes under these restrictions? Here's what we did: Read more ... ## ARP Challenges in EVPN/VXLAN Symmetric IRB DevFeed: [ARP Challenges in EVPN/VXLAN Symmetric IRB]() Original publisher: [Read original article]() Published: 2025-04-03T06:30:00Z Content type: article Language: en Sources: [ipSpace.net blog]() Topics: [evpn](), [VXLAN](), [networking](), [interoperability]() Tags: [arp](), [debugging](), [evpn](), [interoperability](), [netlab](), [networking](), [ospf](), [troubleshooting](), [vxlan]() ### AI overview An EVPN/VXLAN symmetric IRB integration test exposed interoperability issues between Nokia SR Linux or Juniper vSwitch and an FRR container. The article describes the lab topology and initial troubleshooting findings, including ARP behavior that prevented some expected connectivity. ### Source excerpt Whenever I claimed that EVPN is The SIP of Networking, vendor engineers quickly told me that "EVPN interoperability is a solved problem" and that they run regular multi-vendor interoperability labs to iron out the quirks. As it turns out, things aren't as rosy in real life; it's still helpful to have an EVPN equivalent of the DTMF tone generators handy. I encountered a particularly nasty quirk when running the netlab EVPN integration test using symmetric IRB with an anycast gateway between Nokia SR Linux (or Juniper vSwitch) and FRR container. Lab topology Read more ... ## Understanding and Observing the BGP Connect State DevFeed: [Understanding and Observing the BGP Connect State]() Original publisher: [Read original article]() Published: 2025-01-30T06:55:00Z Content type: article Language: en Sources: [ipSpace.net blog]() Topics: [BGP](), [Finite-state machine](), [Cisco]() Tags: [arp](), [bgp](), [cisco](), [how-to](), [machine](), [mpls](), [state](), [tcp]() ### AI overview The article explains why the BGP Connect state is difficult to observe, especially on Cisco IOS, whose implementation predates the state and does not display it. It describes the BGP state transitions and conditions that can cause a peer to remain in Connect long enough to observe, including dropped TCP SYN packets and certain routing or filtering configurations. ### Source excerpt I got this question from Paul: Have you ever seen a BGP peer in the "Connect" state? In 20 years, I have never been able to see or reproduce this state, nor any mention in a debug/log. I am starting to believe that all the documentation is BS, and this does not exist. The BGP Finite State Machine (FSM) (at least the one defined in RFC 4271 and amended in RFC 9687) is "a bit" hard to grasp but the basics haven't changed from the ancient days of RFC 1771: Read more ... ## Comparing IP and CLNP: Finding Adjacent Nodes DevFeed: [Comparing IP and CLNP: Finding Adjacent Nodes]() Original publisher: [Read original article]() Published: 2024-10-17T07:10:00Z Content type: comparison Language: en Sources: [ipSpace.net blog]() Topics: [networking](), [TCP/IP](), [Protocol (disambiguation)](), [data]() Tags: [arp](), [interfaces](), [ip](), [ipv4](), [ipv6](), [network](), [networking](), [networking-fundamentals](), [protocol](), [tcp](), [tcp-ip]() ### AI overview The article compares TCP/IP and CLNP approaches to finding adjacent nodes. TCP/IP uses subnet masks to determine whether a destination is directly reachable and ARP or Neighbor Discovery to resolve the destination link-layer address, while CLNP nodes advertise NSAP addresses through hello messages that neighboring nodes cache. ### Source excerpt Now that we know a bit more about addresses in a networking stack (read the whole series) and why CLNP uses node addresses while TCP/IP uses interface addresses, let's see how they solve common addressing problems like finding adjacent nodes. Let's start with the elephant in the room: how do you know whether you can reach a host you want to communicate with directly? In the following diagram, how does A know whether B is sitting next to it? Read more ...