4A0-D03: Nokia SR Linux EVPN and Data Center InterconnectDemo

Learning a host MAC address in an L2 EVPN produces an EVPN Type 2 MAC/IP Advertisement route. EVPN Type 5 is an IP Prefix route used for Layer 3 prefix advertisement, not for advertising a newly learned Layer 2 host MAC address.

When a locally learned MAC entry ages out on a PE, the PE must withdraw that MAC address from BGP. EVPN MAC-mobility sequence numbers increase for a new local mobility event, while remote PEs use advertised routes rather than requiring MAC-table synchronization.

VXLAN encapsulates Layer 2 traffic over a Layer 3 underlay and uses a 24-bit VNI, allowing up to 16 million isolated overlay segments. UDP entropy can enable ECMP load sharing across underlay paths. EVPN is an optional BGP-based control plane used with VXLAN, rather than the purpose for which VXLAN was developed.

In an all-active EVPN Ethernet segment, exactly one designated forwarder (DF) forwards remotely received broadcast, unknown-unicast, and multicast (BUM) traffic to the multihomed device. Non-DF leafs do not forward that traffic toward the Ethernet segment, preventing duplicate BUM frames.

Interface-less symmetric routing connects IP-VRFs directly through the overlay and uses EVPN Type 5 prefix routes for remote-subnet forwarding. The IP-VRF does not require an anycast-gateway configuration; anycast gateway settings, when used for attached subnets, belong to the IRB gateway interface. Symmetric forwarding performs both MAC and IP lookups at ingress and egress.

A Layer 3 virtual Ethernet Segment configured for all-active multihoming has no Designated Forwarder election; every participating leaf is primary. It also does not use single-active redundancy. AD per-EVI routes advertise primary status, and the third-party prefix advertised by the VNF to Leaf3 is reached through Leaf3. Nokia SR Linux: EVPN for Layer 3

Asymmetric IRB in an EVPN-VXLAN fabric uses EVPN Type 2 MAC/IP advertisements for host reachability. The ingress VTEP routes traffic into the destination VLAN/VNI, so each leaf must have the destination MAC-VRF configured; the MAC-VRFs use IRB interfaces to connect to the Layer 3 IP-VRF. EVPN Type 5 IP-prefix routing is used for the symmetric IRB model, not this asymmetric Type 2 design.

ARP requests may be flooded within the EVPN broadcast domain, but an ARP reply is unicast back toward the original requester rather than replicated to every leaf in the flooding list. EVPN route type 2 advertises learned MAC/IP information between EVPN peers.

EVPN PE-CE routing is normally implemented with eBGP between the PE and CE. CE-learned BGP routes can be re-advertised as EVPN IP Prefix (route type 5) routes, while received EVPN routes require an export policy to be advertised to the CE and CE routes require an import policy to be re-advertised into EVPN. Using iBGP simply because the PE and CE are in the same autonomous system is not the preferred model.

In Nokia’s centralized-router Layer 3 EVPN multihoming design, the leaf routers and the centralized router’s Ethernet segment must operate in single-active mode. An all-active multihoming setting is therefore not a required configuration and conflicts with this design.

EVPN route-reflector client sessions are MP-iBGP overlay sessions. The leaf and route reflector use the common overlay autonomous system for those sessions; a leaf’s eBGP underlay ASN is not the ASN used for route-reflector EVPN peering. Route reflection uses cluster IDs for loop prevention and can use redundant route reflectors.

Duplicate-IP detection is triggered by IP-to-MAC moves within the monitoring window, rather than by a MAC address having been associated with a different IP address. When an IP is declared duplicate, the configured anti-spoof MAC replaces its proxy-ARP entry. With static-blackhole true, that anti-spoof MAC is installed as a blackhole MAC, so matching traffic is discarded during the configured 9-minute hold-down period.

A gratuitous ARP is an unsolicited, local-broadcast ARP announcement that advertises an IP-to-MAC mapping so receiving hosts can refresh applicable ARP-cache entries. It does not require, or cause, acknowledgement replies from the other hosts. RFC 5944 specifies that a gratuitous ARP is transmitted as a local broadcast and that receivers update an existing ARP-cache entry from the sender protocol and hardware addresses.

An EVPN Type 2 MAC/IP Advertisement route may carry only a MAC address when no IP address is encoded; that MAC-only advertisement is used by remote PE devices to establish Layer 2 reachability and MAC forwarding. A subsequent Type 2 route containing 192.168.100.1 provides the MAC/IP binding used for ARP-related functions, but it does not make the earlier MAC-only route irrelevant to MAC forwarding.

Designated-forwarder election controls which PE forwards traffic toward a single-active Ethernet Segment; it does not make the DF the sole originator of EVPN IP Prefix (Type 5) routes. IP Prefix routes advertise learned IP reachability independently of the DF forwarding role.

An EVPN Ethernet Segment route (route type 4) provides multihomed-PE discovery and participates in designated-forwarder election; its DF Election Extended Community can signal the desired election algorithm. All-Active versus Single-Active redundancy mode is instead signaled by the Single-Active flag in the ESI Label Extended Community carried with an Ethernet Auto-Discovery per Ethernet Segment route (route type 1).

An EVPN route type 5 is an IP-prefix route generated and advertised by a PE to remote PEs after the PE learns a local customer-side route. The CE advertises its reachable prefixes to the PE using the selected PE–CE routing method; it does not originate BGP EVPN type 5 routes. Juniper documents that locally learned PE routes are advertised to remote PEs through EVPN type 5.

Asymmetric L3 EVPN forwarding performs the IP route lookup and destination MAC resolution at the ingress PE, while the egress PE performs only MAC forwarding. Because all tenant subnets must be locally represented, every participating PE needs the relevant MAC-VRFs. EVPN Type 5 IP-prefix routes are not required for the asymmetric IRB model; it can use Type 2 MAC/IP advertisements instead.

In single-active (active-standby) EVPN multihoming, DF election selects the active PE for the Ethernet segment and MAC-VRF. The DF handles traffic toward and from the multihomed CE, including BUM traffic sent from remote PEs. Remote PEs direct unicast flows to the DF and use the non-DF only as a backup PE, so the non-DF does not forward that remote unicast traffic to the host.

A route distinguisher makes EVPN/VPN route NLRIs unique, allowing MP-BGP to distinguish overlapping tenant address information. It is configured uniquely for an EVPN instance on a PE and is carried in EVPN route NLRIs. Route Targets determine control-plane membership and route import/export, rather than the route distinguisher identifying the EVPN instance for that purpose.

EVPN single-active multihoming permits only one VTEP attached to an Ethernet segment to forward traffic to and from that segment; Leaf1 is the active designated forwarder and Leaf2 is standby. The host-facing interfaces are associated with ES-1, but single-active operation does not inherently require the host to use a LAG.