1. EVC
Atahar Khan
CCIE SP 44012
Cisco Systems

2. Agenda
L2VPN overview Ethernet Virtual Circuits (EVC)

3. L2VPN Overview

4. What is L2VPN ?
We call L2VPN any method which allow to have a LAN shared across multiple remote location across a non L2 network
The network in the middle can be :
IPv4 Routed network  L2TPv3 can be use
MPLS network  EoMPLS or VPLS
Another switched Network  QinQ
The PE to CE interface might not be Ethernet
Atom : tunnel of anything over MPLS network
L2TPv3 : encapsulate anything over ipv4 network
Interworking : allow to interconnect one L2 tech to another (FR to ATM or Eth to ATM or…)
Those technique can be combined to achieve LAN transparency !
Cisco Systems

5. L2VPN Models L2TPv3 AToM L2-VPN Models MPLS Core IP core VPWS VPLS
P2MP/ MP2MP
Point-to-Point
Point-to-Point
Ethernet FR
ATM AAL5/Cell
PPP/ HDLC FR
ATM AAL5/Cell
PPP/ HDLC
Ethernet
Ethernet

6. Virtual Private Wire Service (VPWS) Reference Model
L2transport over IP = L2TPv3
L2transport over MPLS = AToM
SE = Service Endpoint
Customer Site
PSN = Packet Switched Network
Customer Site
PSN Tunnel
PWES
Pseudo Wires
PWES PE PE
PWES
Customer Site
PWES
Customer Site
Emulated Service
A Pseudowire (PW) is a connection between two Provider Edge (PE) devices which connects two pseudowire End-Services (PWESs) of the same type
Service Types:
Ethernet
802.1Q (VLAN)
ATM VC or VP
HDLC
PPP
Frame Relay VC
PWES
Cisco Systems

7. Ethernet Virtual Circuits (EVC)

8. The Challenges
On traditional switches, we require the switch to do two things:
1.) Have the VLAN configured globally
2.) Perform MAC learning in this VLAN
switches have a finite amount of CAM space for MAC Learning limiting the number of hosts we can support.
Since the 802.1q VLAN tag is only 12-bits wide we can only configure a maximum of 4096 VLANs.
In modern provider and cloud environments there is a need to scale beyond these limitations.
VLAN translation can not be done.
Cisco Systems

9. EVC Advantages
The VLAN tag is used for classification and the Service Instance defines the forwarding action.
we could allocate one VLAN to different customers on every switchport and forward each customer's traffic across different MPLS Pseudowires, but never actually configure the VLAN globally.
Customer VLAN ID preservation/ translation.
Cisco Systems

10. CE-VLAN ID Preservation Application (1)
ERS services with same End to End CE-VLAN ID
Cisco Systems

11. CE-VLAN ID Preservation Application (2)
Corporate Customers with all remote offices using the same CE-VLAN ID
Also useful for SP deploying Managed CPEs
NEED OF VLAN TRANSLATION !!!
Cisco Systems

12. EVC – Flexible Frame Matching
Service instance
Service instance ...
Provide classification of L2 flows on Ethernet interfaces
Are also referred to as EVC service-instances
Support dot1q and Q-in-Q
Support VLAN lists
Support VLAN ranges
Support VLAN Lists and Ranges combined
Coexist with routed subinterfaces
Match
VLAN: 14 14
100
Match VLAN range:
101
102
200
Match
VLAN list: 200, 203, 210
203
INTERFACE
210
Match
VLAN: 300,100
300,100
400,1
Match
outer VLAN 400,
inner VLAN range: 1-3
400,2
400,3
400,11
Match
outer 400,
inner VLAN list:
11,17,34
400,17
400,34
Cisco Systems

13. Exact vs. Non-Exact EVC only supports Non-Exact matching
‘encap dot1q 10’ matches any packets with outmost tag equals to 10:
‘encap dot1q 10 sec 100’ matches any packets with outmost tag as 10 and second most tag as 100 10 10
200 10
100 10
1000
100
Cisco Systems

14. Longest tag match Int G3/0/0
EVC supports longest tag matching within the same GigE port. Matching double tag at first, then single tag, then default tag (similar concept as routing table lookup) 10
dot1q 10
sec 100
sec 10
200 10
100
Int G3/0/0 10
130
Cisco Systems

15. EVC – Flexible VLAN Tag Manipulation
EVCs allow us to classify inbound frames in a highly flexible manner based on 1 or more VLAN tags or CoS values. Here are some examples
Configuration
Effect
encapsulation dot1q 10
Match the single VLAN tag 10
encapsulation dot1q 25 second-dot1q 13
Match first VLAN tag 25 and second tag 13
encapsulation dot1q any second-dot1q 22
Match any double tagged frame with a second tag of 22
encapsulation dot1q 16 cos 4
Match a single tag 16 when it has CoS value 4
encapsulation dot1q untagged
Match the native (untagged) VLAN
encapsulation dot1q default
The catch all class for all traffic not previously classified
Cisco Systems

16. Encap match order From most specific to most general
No exact match based on outmost tag #
Encap untag matches untagged packet
Encap default catches all remaining traffic w/o specific match. If there is no encap untag configured, it also catches untag packet.
Cisco Systems

17. Encapsulation Rewrite CLI
interface gig 1/1/1
service instance 1 ethernet
encapsulation dot1q 10
rewrite ingress tag ?
pop Pop the tag
push Rewrite Operation of push
translate Translate Tag .
Configuration
Effect
rewrite ingress tag pop 1 symmetric
remove the top 802.1q tag
rewrite ingress tag pop 2 symmetric
remove the top two 802.1q tags
rewrite ingress tag translate 1-to-1 dot1q  28 symmetric
remove the top tag and replace it with 28
rewrite ingress tag translate 2-to-2 dot1 22 second-dot1q 23
remove the top two tags and replace them with 22 and 23 (23 will be the inner tag)
rewrite ingress tag push dot1q 56 second-dot1q 55
push two new tags on top of the existing frame. The top tag will be 56; inner tag of 55
Cisco Systems

18. Encapsulation Rewrite CLI - Symmetric.
Cisco Systems

19. Here's a sample topology, with two access switches processing different VLANs. The service instance configurations are on PE Blue and PE Purple

20. EVC – Flexible Forwarding Model
Service instance
P-to-P Local Connect
MPLS
L3/VRF or EoMPLS/VPLS BD
SVI
MPLS
UPLINK
P-to-P EoMPLS BD
EoMPLS/VPLS
SVI BD
L2 Bridging
PVC / DLCI
L2 inter-working
Physical Ports
ATM / FR

21. Flexible Service Mapping Configuration Example
core interface, L2 trunk or L3 MPLS
Access port
service instance 1 ethernet
encapsulation dot1q 20 second-dot1q 10
rewrite ingress tag pop 1 sym
bridge-domain 10 c-mac
802.1ah (PBB or .1ah over VPLS
service instance 2 ethernet
encapsulation dot1q
rewrite ingress tag push dot1q 101
xconnect en mpls
E-LINE (VPWS)
service instance 3 ethernet
encapsulation dot1q 101 second-dot1q 10
rewrite ingre tag translate 2-to-1 100
bridge-domain 200
Interface vlan 200
xconnect vfi myvpls
E-LAN (VPLS or Local bridging)
Local connect
service instance 4 ethernet
encapsulation dot1q 102
rewrite ingress tag pop 1
bridge-domain 201
Interface vlan 201
ip address
ip vrf myvrf
L3 termination
Service instance or Ethernet Flow Point
Cisco Systems

22. EVC (Service Instance) Example
Here is an example of an interface configured with a bridge-domain:
interface g0/2
  service instance 1 ethernet
    encapsulation dot1q 11
    rewrite ingres tag pop 1 symmetric
    bridge-domain 22 !
interface Vlan22
  ip address

23. EVC – Local & remote bridging example
LOCAL Switching
interface g0/2
  service instance 1 ethernet
    encapsulation dot1q 10
    rewrite ingres tag pop 1 symmetric
    bridge-domain 22
  service instance 2 ethernet
    encapsulation dot1q 11
    rewrite ingress tag pop 1 symmetric
   bridge-domain 22 !
interface Vlan44
  ip address
Remote Connection
interface g0/2
  service instance 1 ethernet
    encapsulation dot1q 10
    rewrite ingres tag pop 1 symmetric
    bridge-domain 22 split-horizon
  service instance 2 ethernet
    encapsulation dot1q 11
    rewrite ingress tag pop 1 symmetric !
interface Vlan44
 xconnect encapsulation mpls
Cisco Systems

24. Cisco Systems