Tag :: Multihoming

EVPN route advertisements carry RD and RT. RD (Route Distinguisher) : prepend to the tenant’s IP Prefix or MAC address to make it globally unique. RT (Route Target) : a BGP extended community used to tag the EVPN route.  The EVPN import policy is chosen to select what is the target tenant VRF is imported from the global EVPN table.

EVPN Multihoming defines a mechanism for Multihoming PEs to quickly signal, to remote PEs, a failure in an Ethernet Segment (ES) connectivity with the use of Ethernet A-D per ES route

Multihoming in EVPN allows a single customer edge (CE) to connect to multiple provider edges (PE or tunnel endpoint). These PE devices are all connected to the same Ethernet-Segment (ES). Multihoming is activated by assigning a unique Ethernet Segment Identifier (ESI) and ES-Import Route Target (RT) which enables all the PEs connected to the same multihomed site to import the Type 4 ES routes

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 VXLAN all-active multihoming (AA-MH) provides redundancy to reduce or eliminate the impact of outages and maintenance. The objective of Maintenance Mode on AA-MH is to gracefully drain away the traffic from the EVPN core flowing through a switch that is part of multihoming while the switch is put into maintenance, and to gracefully add it back into the network and attract traffic again once the switch is out of maintenance. During the maintenance cycle any customer edge Ethernet or Port-Channel interfaces, whether they are participating as ethernet segments or not, can also be put into maintenance mode. Doing so eliminates the northbound traffic from the customer edge from flowing through the switch under maintenance. The traffic will instead take a path through other available multi-homing peers.

[L2 EVPN] and  [Multicast EVPN IRB] solutions allow for the delivery of customer BUM (Broadcast, Unknown unicast

PIM External Gateways (PEGs) allow an EVPN overlay multicast network to interface with an external PIM domain. They can be used to interconnect two data centers using an external PIM domain in between them.