• Tag : BFD

 
 

BFD troubleshooting tips

BFD quick introduction: What is BFD? Bidirectional Forwarding Detection(BFD) is a low overhead protocol designed to provide rapid detection of failures in the path between adjacent forwarding engines over any media and at any protocol layer – this base protocol is defined in RFC5880. It does not operate independently, but only as an adjunct to routing protocols Operation: BFD is a simple Hello protocol that involves  a pair of systems transmitting BFD packets periodically over a path between the two systems, and if a system stops receiving BFD packets  for long enough , that bidirectional path is assumed to have...
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Support BGP PIC edge for EVPN VXLAN routes for remote VTEP failures

Description Prior to 4.25.2F, support for BGP PIC was restricted to locally identifiable failures such as link failures. If a remote VTEP went down, this would require action by the IGP and BGP to recompute a new best path traffic destined to affected BGP prefixes originally reachable by the problematic VTEP. This feature introduces support for RFC8971 (BFD for VXLAN) for EVPN learned VTEPs to improve convergence times in these scenarios by tying the liveness detection provided by the BFD sessions into existing BGP PIC support for software fast-failover. Without this feature, until the underlay route providing reachability to the...
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BFD session telemetry

Description BFD (Bidirectional Forwarding Detection) session telemetry allows for the collection of per-session statistics as well as rbfd kernel module statistics to be automatically collected at a set interval and stored in shared memory where Cloud Vision Portal (CVP) or other applications may gather them.  Previously, this information was only available to the user via execution of several CLI show-commands.  In addition, several new statistics have been added which are updated within the session-stats interval and provide a finer “snapshot” view of session health than the previously-available session lifetime statistics.  This feature supports both hardware-accelerated and software (kernel module) accelerated...
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Modal BFD CLI configuration

Description A new configuration model for the BFD (Bidirectional Forwarding Detection) agent was added in order to more concisely group configuration commands.  In addition to isolating BFD-specific CLI commands from the rest of the system configuration, using a dedicated configuration mode allows for new sub-modes to be added for peer-specific configuration that pertains to either the default VRF or a non-default VRF.  This allows for a finer control of BFD-specific settings.  System-wide BFD configuration exists in three contexts: Interface-level BFD configuration, Global BFD configuration, and Peer-level BFD configuration. Global BFD configuration commands are entered within the scope of the new...
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Support for BGP Peer Flap Damping

Description This document describes the Bgp Peer Flap Damping feature which allows session damping for peers with bfd enabled. BGP takes a long time to detect failures such as failing links due to longer keepalive/hello time-out values. It takes advantage of detecting link failures faster by receiving notification through BFD. This is very useful until we are faced with a link flapping scenario, as it will cause BGP sessions to establish and break down over and over, causing unnecessary traffic loss and churn.  This feature allows delaying establishment of BGP sessions during BFD flapping, which ends up reducing traffic loss...
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BFD support in vEOS lab

When I tried to run the following BFD interval command under global scope in vEOS, I got error: bfd interval 1200 min_rx 1200 multiplier 3 % Incomplete command Can you give me hint what the correct syntax is?   Thanks  

Seamless BFD for SR-TE policies

Description Bidirectional Forwarding Detection (BFD) is a protocol that provides low-overhead, short-duration detection of failures of arbitrary paths between two systems. Seamless Bidirectional Forwarding Detection (S-BFD) defines a simplified mechanism for using BFD with a large proportion of negotiation aspects eliminated, thus providing benefits such as quick provisioning and improved control and flexibility for network nodes initiating path monitoring. Segment Routing Traffic Engineering Policy (SR-TE) makes use of Segment Routing to allow a headend to steer traffic along any path without maintaining per flow state in every node. A headend steers traffic into an “SR-TE tunnel”. Currently, traffic is forwarded...
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Regarding Arista BFD Parameters

Hello, We are implementing bfd between Arista to Arista and Arista to Juniper for BGP. We see abnormal behavior with Your Disc and My Disc parameters. So looking at the bfd neighbors out put. If devices running 4.17.5M, the Your/My Disc numbers are small. If Devices are running 4.20.10M or 4.23.3M then the numbers are very high. What do those numbers indicate ?

Hardware Accelerated BFD Transmit

Description This feature adds support for offloading BFD Transmit path to hardware (ASIC) for specific types of BFD sessions. This will improve accuracy of transmit timer implementations for BFD (especially with fast timers like 50 ms) and relieve pressure on the main CPU in scenarios of scale.   On supported platforms, hardware acceleration-capable BFD sessions will be offloaded by default. Memory resources are required on ASIC to offload sessions (one unit per discriminator). Currently, the number of session discriminators that can be offloaded is restricted to 200 per ASIC.   Only single-hop BFD sessions on front panel ports are capable...
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Hardware Accelerated BFD Transmit

Description This feature adds support for offloading BFD Transmit path to hardware (ASIC) for specific types of BFD sessions. This will improve accuracy of transmit timer implementations for BFD (especially with fast timers like 50 ms) and relieve pressure on the main CPU in scenarios of scale. Note that RX packet processing for all BFD sessions is still handled by the Bfd agent on the main CPU. The feature does not add any additional timer interval or multiplier configurations. On supported platforms, hardware acceleration-capable BFD sessions will be offloaded by default. Memory resources are required on ASIC to offload sessions...
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IS-IS BFD

Does Arista EOS suppport ISIS BFD? If not, then are there any plans to support it and when? Thanks, Laszlo

BFD SSO

Description BFD Stateful Switchover (SSO) allows for a switchover from an active supervisor to a standby supervisor where BFD sessions do not flap on the router undergoing the SSO, or the router that is the BFD peer. If BGP is configured with a BFD neighbor and with graceful restart, then BGP routes will not flap during SSO. If IS-IS is configured with an IPv4 BFD neighbor and with graceful restart, then IS-IS adjacencies will not flap during SSO. BFD echo mode may or may not be required to be configured on the peer depending on the scenario. Prior to EOS-4.23.2F,...
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BFD Enhancements

As of EOS-4.17.0F, BFD support has been enhanced with support for configuring BFD within VRFs, improved scalability and cleanly disabling BFD sessions. This latter enhancement, referred to as AdminDown support, makes it possible to disable BFD configurations without the remote peer interpreting the BFD state change as a session failure. In most instances this non-disruptive BFD disablement is performed automatically upon changing the BFD configuration. Situations which would still be disruptive are cases where the interface which the BFD session is operating over is disabled or reconfigured to be incompatible with BFD. Examples include, the switchport or no vlan 1234...
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OSPFv3 BFD

EOS-4.17.0F adds support for BFD in OSPFv3. BFD provides a faster convergence in scaled deployments where using aggressive times may cause scalability issues. This also addresses scenarios which need sub-second hello timers , which is not supported in EOS. Platform compatibility OSPFv3 BFD feature is supported on all platforms. Configuration This feature can be configured in two ways. The following command is available under the config-router-ospf3 mode. Arista(config)#ipv6 router ospf <Ospf Process ID> Arista(config-router-ospf3)#[ no | default ] bfd all-interfaces This enables or disables BFD for all OSPFv3 interfaces. It is disabled by default. The following command is available under...
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