L2VPN and Ethernet Services Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 7.2.x
Bias-Free Language
The documentation set for this product strives to use bias-free language. For the purposes of this documentation set, bias-free is defined as language that does not imply discrimination based on age, disability, gender, racial identity, ethnic identity, sexual orientation, socioeconomic status, and intersectionality. Exceptions may be present in the documentation due to language that is hardcoded in the user interfaces of the product software, language used based on RFP documentation, or language that is used by a referenced third-party product. Learn more about how Cisco is using Inclusive Language.
The EVPN-VPWS is a BGP control plane solution for point-to-point
services. It implements the signaling and encapsulation techniques for
establishing an EVPN instance between a pair of PEs. It has the ability to
forward traffic from one network to another without MAC lookup. The use of EVPN
for VPWS eliminates the need for signaling single-segment and multi-segment PWs
for point-to-point Ethernet services. The EVPN-VPWS technology works on IP and
MPLS core; IP core to support BGP and MPLS core for switching packets between
the endpoints.
EVPN-VPWS support both single-homing
and multi-homing.
Supported Modes for EVPN-VPWS
EVPN-VPWS supports the following modes:
Single-homed - Enables you to connect a customer edge (CE) device to one provider edge (PE) device.
Multi-homed - Enables you to connect a customer edge (CE) device to more than one provider edge (PE) device. Multihoming ensures
redundant connectivity. The redundant PE device ensures that there is no traffic disruption when there is a network failure.
Following are the types of multihoming:
Single-Active - In single-active mode only a single PE among a group of PEs attached to the particular Ethernet-Segment is
allowed to forward traffic to and from that Ethernet Segment.
All-Active - In all-active mode all the PEs attached to the particular Ethernet-Segment is allowed to forward traffic to and
from that Ethernet Segment.
EVPN-VPWS Single
Homed
The EVPN-VPWS single homed solution requires per EVI Ethernet Auto
Discovery route. EVPN defines a new BGP Network Layer Reachability Information
(NLRI) used to carry all EVPN routes. BGP Capabilities Advertisement used to
ensure that two speakers support EVPN NLRI (AFI 25, SAFI 70) as per RFC 4760.
The architecture for EVPN VPWS is that the PEs run Multi-Protocol BGP in
control-plane. The following image describes the EVPN-VPWS configuration:
The VPWS service on PE1 requires the following three elements to be
specified at configuration time:
The VPN ID (EVI)
The local AC identifier (AC1) that identifies the local end of
the emulated service.
The remote AC identifier (AC2) that identifies the remote end of
the emulated service.
PE1 allocates a MPLS label per local AC for reachability.
The VPWS service on PE2 is set in the same manner as PE1. The three
same elements are required and the service configuration must be symmetric.
PE2 allocates a MPLS label per local AC for reachability.
PE1 advertise a single EVPN per EVI Ethernet AD route for each local
endpoint (AC) to remote PEs with the associated MPLS label.
PE2 performs the same task.
On reception of EVPN per EVI EAD route from PE2, PE1 adds the entry
to its local L2 RIB. PE1 knows the path list to reach AC2, for example, next
hop is PE2 IP address and MPLS label for AC2.
PE2 performs the same task.
Configure EVPN-VPWS
Single Homed
This section describes
how you can configure single-homed EVPN-VPWS feature.
The EVPN VPWS feature
supports all-active multihoming capability that enables you to connect a
customer edge device to two or more provider edge (PE) devices to provide load
balancing and redundant connectivity. The load balancing is done using
equal-cost multipath (ECMP).
When a CE device is
multi-homed to two or more PEs and when all PEs can forward traffic to and from
the multi-homed device for the VLAN, then such multihoming is referred to as
all-active multihoming.
Consider the topology
in which CE1 is multi-homed to PE1 and PE2; CE2 is multi-homed to PE3 and PE4.
PE1 and PE2 will advertise an EAD per EVI route per AC to remote PEs which is
PE3 and PE4, with the associated MPLS label. The ES-EAD route is advertised per
ES (main interface), and it will not have a label. Similarly, PE3 and PE4
advertise an EAD per EVI route per AC to remote PEs, which is PE1 and PE2, with
the associated MPLS label.
Consider a traffic
flow from CE1 to CE2. Traffic is sent to either PE1 or PE2. The selection of
path is dependent on the CE implementation for forwarding over a LAG. Traffic
is encapsulated at each PE and forwarded to the remote PEs (PE 3 and PE4)
through MPLS core. Selection of the destination PE is established by flow-based
load balancing. PE3 and PE4 send the traffic to CE2. The selection of path from
PE3 or PE4 to CE2 is established by flow-based load balancing.
If there is a failure
and when the link from CE1 to PE1 goes down, the PE1 withdraws the ES-EAD
route; sends a signal to the remote PEs to switch all the VPWS service
instances associated with this multi-homed ES to backup PE, which is PE2.
Configure EVPN-VPWS Single-Active Multi-Homed
This section describes how to configure single-active multi-homed EVPN-VPWS feature. You can enable the single-active mode
by using the load-balancing-mode single-active command.
/* On PE1 */
!
configure
l2vpn xconnect group evpn_vpws
p2p e1_5-6
interface Bundle-Ether10.2
neighbor evpn evi 1 target 5 source 6
!
evpn
interface Bundle-Ether10
ethernet-segment
identifier type 0 00.01.00.ac.ce.55.00.0a.00
!
/* On PE2 */
!
configure
l2vpn xconnect group evpn_vpws
p2p e1_5-6
interface Bundle-Ether10.2
neighbor evpn evi 1 target 5 source 6
!
evpn
interface Bundle-Ether10
ethernet-segment
identifier type 0 00.01.00.ac.ce.55.00.0a.00
!
/* On PE3 */
!
configure
l2vpn xconnect group evpn_vpws
p2p e1_5-6
interface Bundle-Ether20.1
neighbor evpn evi 1 target 6 source 5
!
evpn
interface Bundle-Ether20
ethernet-segment
identifier type 0 00.01.00.ac.ce.55.00.14.00
!
/* On PE4 */
!
configure
l2vpn xconnect group evpn_vpws
p2p e1_5-6
interface Bundle-Ether20.1
neighbor evpn evi 1 target 6 source 5
!
evpn
interface Bundle-Ether20
ethernet-segment
identifier type 0 00.01.00.ac.ce.55.00.14.00
!
Flow Label Support for EVPN VPWS
The Flow Label support for EVPN VPWS feature enables provider (P) routers to use the flow-based load balancing to forward
traffic between the provider edge (PE) devices. This feature uses Flow-Aware Transport (FAT) of pseudowires (PW) over an MPLS
packet switched network for load-balancing traffic across BGP-based signaled pseudowires for Ethernet VPN (EVPN) Virtual Private
Wire Service (VPWS).
FAT PWs provide the capability to identify individual flows within a PW and provide routers the ability to use these flows
to load-balance the traffic. FAT PWs are used to load balance the traffic in the core when equal cost multipaths (ECMP) are
used. A flow label is created based on indivisible packet flows entering an imposition PE. This flow label is inserted as
the lower most label in the packet. P routers use the flow label for load balancing to provide better traffic distribution
across ECMP paths or link-bundled paths in the core. A flow is identified either by the source and destination IP address
of the traffic, or the source and destination MAC address of the traffic.
The following figure shows a FAT PW with two flows distributing over ECMPs and bundle links.
An extra label is added to the stack, called the flow label, which is generated for each unique incoming flow on the PE. A
flow label is a unique identifier that distinguishes a flow within the PW, and is derived from source and destination MAC
addresses, and source and destination IP addresses. The flow label contains the end of label stack (EOS) bit set. The flow
label is inserted after the VC label and before the control word (if any). The ingress PE calculates and forwards the flow
label. The FAT PW configuration enables the flow label. The egress PE discards the flow label such that no decisions are made.
Core routers perform load balancing using the flow-label in the FAT PW with other information like MAC address and IP address.
The flow-label adds greater entropy to improve traffic load balancing. Therefore, it is possible to distribute flows over
ECMPs and link bundles.
In this topology, the imposition router, PE1, adds a flow label in the traffic. The disposition router, PE2, allows mixed
types of traffic of which some have flow label, others do not. The P router uses flow label to load balance the traffic between
the PEs. PE2 ignores the flow label in traffic, and uses one EVPN label for all unicast traffic.
Restrictions
To configure flow label for EVPN VPWS, the following restrictions are applicable:
This feature is not supported for EVPN Point-to-Multipoint (P2MP) of VPLS and Ethernet LAN (E-LAN) service.
This feature is supported only for EVPN VPWS single homing. AC bundle interfaces must be configured with ESI-0 only.
This feature is not supported for EVPN flexible cross-connect service.
This feature is not supported for EVPN VPWS multihoming.
Configure Flow Label for EVPN VPWS
Configuration Example
Perform this task to configure flow label for EVPN VPWS on both PE1 and PE2.
This section shows the running configuration of flow label for EVPN VPWS.
l2vpn
xconnect group evpn-vpws
p2p evpn1
interface TenGigE0/0/0/0
neighbor evpn evi 1 target 2 source 1
!
!
evpn
evi 1
control-word-disable
load-balancing
flow-label static
!
!
Verification
Verify EVPN VPWS flow label configuration.
Router# show l2vpn xconnect detail
Group evpn-vpws, XC evpn1, state is up; Interworking none
AC: TenGigE0/0/0/0, state is up
Type Ethernet
MTU 1500; XC ID 0x1; interworking none
Statistics:
packets: received 21757444, sent 0
bytes: received 18226521128, sent 0
EVPN: neighbor 100.100.100.2, PW ID: evi 1, ac-id 2, state is up ( established )
XC ID 0xc0000001
Encapsulation MPLS
Encap type Ethernet, control word disabled
Sequencing not set
LSP : Up
Flow Label flags configured (Tx=1,Rx=1) statically
EVPN Local Remote
------------ ------------------------------ -----------------------------
Label 64002 64002
MTU 1500 1500
Control word disabled disabled
AC ID 1 2
EVPN type Ethernet Ethernet
------------ ------------------------------ -----------------------------
Create time: 30/10/2018 03:04:16 (00:00:40 ago)
Last time status changed: 30/10/2018 03:04:16 (00:00:40 ago)
Statistics:
packets: received 0, sent 21757444
bytes: received 0, sent 18226521128