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EVC
Atahar Khan
CCIE SP 44012
AGENDA
L2VPN overview
Ethernet Virtual Circuits (EVC)
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L2VPN Overview
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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 !
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L2VPN Models
AToM
L2TPv3
L2-VPN Models
MPLS Core
VPWS
IP core
VPLS
P2MP/
MP2MP
Point-to-Point
Point-to-Point
Ethernet
FR
ATM
AAL5/Cell
Ethernet
PPP/
HDLC
FR
ATM
AAL5/Cell
Ethernet
PPP/
HDLC
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Virtual Private Wire Service (VPWS) Reference Model
L2transport over IP = L2TPv3
L2transport over MPLS = AToM
SE = Service Endpoint
Customer
Site
Customer
Site
PSN = Packet Switched Network
PSN Tunnel
PWES
Pseudo Wires
PE
PWES
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
• HDLC
• 802.1Q (VLAN)
• PPP
• ATM VC or VP
PWES
• Frame Relay VC
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Ethernet Virtual Circuits (EVC)
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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.
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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.
CE-VLAN ID Preservation Application (1)
ERS services with same End to End CE-VLAN ID
VLAN Mapping
Points
Customer
CE-1
MEN
Customer
200
CE-2
100
CE-HQ 200
300
CE-VLAN ID
Customer
100
Customer
300
CE-3
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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
Customer
100
NEED OF VLAN TRANSLATION !!!
Customer
VLAN Mapping
Points
MEN
Customer
100
CE-2
600
CE-HQ 601
602
CE-VLAN ID
CE-1
Customer
100
CE-3
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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
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100
101
102
200
203
Match
VLAN: 14
Match
VLAN range:
100-102
Match
VLAN list:
200, 203, 210
210
300,10
0
Match
VLAN: 300,100
400,1
Match
outer VLAN 400,
inner VLAN
range: 1-3
400,2
400,3
400,11
400,17
400,34
Match
outer 400,
inner VLAN list:
11,17,34
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Exact vs. Non-Exact
• EVC only supports Non-Exact matching
• ‘encap dot1q 10’ matches any packets with outmost tag equals to
10:
10
10
200
• ‘encap dot1q 10 sec 100’ matches any packets with outmost tag as
10 and second most tag as 100
10
100
10
100
1000
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Longest tag match
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
10
200
dot1q 10
10
100
sec 100
dot1q 10
10
130
sec 128-133
Int G3/0/0
dot1q 10
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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
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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.
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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
rewrite ingress tag pop 1 symmetric
rewrite ingress tag pop 2 symmetric
Effect
remove the top 802.1q tag
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 remove the top two tags and replace them
second-dot1q 23
with 22 and 23 (23 will be the inner tag)
push two new tags on top of the existing
rewrite ingress tag push dot1q 56 secondframe. The top tag will be 56; inner tag of
dot1q 55
55
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Encapsulation Rewrite CLI - Symmetric
.
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Here's a sample topology, with two access switches processing different VLANs.
The service instance configurations are on PE Blue and PE Purple
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EVC – Flexible Forwarding Model
Service
instance
BD
MPLS
P-to-P Local Connect
L3/VRF or
EoMPLS/VPLS
MPLS
UPLINK
SVI
P-to-P EoMPLS
BD
BD
EoMPLS/VPLS
SVI
L2 Bridging
PVC / DLCI
Physical Ports
L2 inter-working
ATM / FR
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Flexible Service Mapping Configuration Example
Access port
Local
connect
Service instance or
Ethernet Flow Point
core interface, L2
trunk or L3 MPLS
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 11-100
rewrite ingress tag push dot1q 101
xconnect 1.1.1.1 101 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)
service instance 4 ethernet
encapsulation dot1q 102
rewrite ingress tag pop 1
bridge-domain 201
Interface vlan 201
ip address 2.2.2.2 255.255.255.0
ip vrf myvrf
L3 termination
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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 192.168.1.1 255.255.255.0
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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 192.168.1.1 255.255.255.0
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
bridge-domain 22 split-horizon
!
interface Vlan44
xconnect 192.168.1.1 12 encapsulation mpls
Thank You