Tag :: STP

When a switchport receives its own STP BPDU, the port goes into role ‘Backup’ and state ‘Discarding’. The

Ethernet VPN (EVPN) networks normally require some measure of redundancy to reduce or eliminate the impact of outages and maintenance. RFC7432 describes four types of route to be exchanged through EVPN, with a built-in multihoming mechanism for redundancy. Prior to EOS 4.22.0F, MLAG was available as a redundancy option for EVPN with VXLAN, but not multihoming. EVPN multihoming is a multi-vendor standards-based redundancy solution that does not require a dedicated peer link and allows for more flexible configurations than MLAG, supporting peering on a per interface level rather than a per device level. It also supports a mass withdrawal mechanism to minimize traffic loss when a link goes down.

EVPN gateway support for all-active (A-A) multihoming adds a new redundancy model to our multi-domain EVPN solution introduced in [1]. This deployment model introduces the concept of a WAN Interconnect Ethernet Segment identifier (WAN I-ESI). The WAN I-ESI allows the gateway’s EVPN neighbors to form L2 and L3 overlay ECMP on routes re-exported by the gateways. The identifier is shared by gateway nodes within the same domain (site) and set in MAC-IP routes that cross domain boundaries.

Arista MLAG supports STP for Layer 2 loop detection. In fact, most customers enable STP in their MLAG(s) to ensure no

Spanning Tree Protocol requires each interface to have a unique port number ranging from 1 through 4095.  Arista STP typically assigns port numbers to port-channel interfaces in the order in which they are configured.

The new feature maintains STP restartability while a portfast-enabled port’s link status changes. In older releases, when portfast is enabled on an interface and the interface is flapping, i.e., going up and down, STP becomes non-restartable. After the new feature is introduced, STP remains restartable during port flapping. This may be applicable in several scenarios, but the most common usage is to keep STP restartable after endpoints are connected and disconnected. This feature is important for SSU because an SSU can only be performed while STP is restartable. After the portfast port's link status changes, SSU can still be conducted.

Leaf Smart System Upgrade (SSU) provides the ability to upgrade the EOS image with minimal traffic disruption. To perform the SSU, Spanning Tree Protocol (STP) should either be disabled or configured as MSTP. Meanwhile, all ports should be configured with admin edge ports (i.e., all ports are supposed to connect to host only) and the BPDU guard should be enabled for all edge ports.