Metro Ethernet

Answered Question
Jul 11th, 2009

Hi,

Does Metro Ethernet support multiple VLANs which are in the two different location?

e.g.

In site A

192.168.1.0/24

192.168.2.0/24

192.168.3.0/24

192.168.4.0/24

Site B:

192.168.1.0/24

192.168.2.0/24

192.168.3.0/24

192.168.4.0/24

There is one Metro Ethernet link up site A and Site B.

If so, how to route the local LAN traffic to Metro Ethernet?

rdgs

Correct Answer by Edison Ortiz about 7 years 7 months ago

I can't answer for him, but you can share the same subnet over a MetroE link.

To reiterate, treat a MetroE link like a physical link between switches. MetroE will be transparent to your L2/L3 design as you can extend these L2/L3 domains over the MetroE connection.

On your design, you need to take into account overlapping IP address assignment thus if you had a DHCP server on Site A handing out addresses and another on Site B handing out same addresses, those issues need to be corrected - same goes for static IP address assignment.

Any Network Engineer would spot this issue during the design but I believe it's worth mentioning for clarity.

__

Edison.

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ciscotech4u Sat, 07/11/2009 - 07:35

Hi Anita,

Depends upon a fundamental factor. that how these sites A & B connected using metro ethernet , if you are hiding sites behind some form of NAT then they may work provided they have thier routing doman. but if both sites are connected without NAT and part of same routing network then you may find routing conflict as both sites cannot share same network.

Rgds,kunwar

anitachoi3 Sat, 07/11/2009 - 07:50

Hi,

If the NAT is deployed, how to config it? how to teach the switch the ip address to be in site B, not in local (site A)?

rdgs

Edison Ortiz Sat, 07/11/2009 - 08:30

You don't have to route the traffic on the MetroE if you want to share the same Vlans on different locations.

On the CEs, configure the ISP facing switchport as 802.1q and allow the Vlans listed above as part of the trunk.

Think of MetroE with the same concept as connecting 2 switches in your DataCenter.

HTH,

__

Edison.

anitachoi3 Sat, 07/11/2009 - 08:50

Hi Edison,

The MetroE is connected to ethernet switch not router, isn't it?

If so, I config the switch port to be a trunk port and connect the MetroE.

Is it correct?

rdgs

Joseph W. Doherty Sat, 07/11/2009 - 13:05

For what Edison is suggesting, you should confirm whether your MetroE provider will pass your VLAN IDs to your far side. Ask about "QinQ" support.

anitachoi3 Sat, 07/11/2009 - 19:07

Hi,

The white paper is more on the provider side to offer the Metro Ethernet service. It includes the router and switch. Regarding the network design (from the white paper), the router is required to connect the CE router. Detail please find the figure 4 - figure 7.

From the customer side, our service provider will give me "dot1Q 3615", that's all. How do I put the 4 class C to Metro Ethernet? It will appricate the sample config to be suggested.

rdgs

Edison Ortiz Sat, 07/11/2009 - 19:43

interface fx/x

switchport trunk encapsulation dot1q

switchport trunk native vlan 3615

switchport mode trunk

switchport trunk allowed vlan [enter the Vlans allowed in the trunk]

HTH,

__

Edison.

anitachoi3 Sun, 07/12/2009 - 06:39

Hi Edison,

Regarding the message from "ciscotech4u - TCS - Jul 11, 2009, 8:35am PST", it mentioned that "but if both sites are connected without NAT and part of same routing network then you may find routing conflict as both sites cannot share same network"

according the meaning, it cannot share same networks via Metro Ethernet, is it?

rdgs

Correct Answer
Edison Ortiz Sun, 07/12/2009 - 07:18

I can't answer for him, but you can share the same subnet over a MetroE link.

To reiterate, treat a MetroE link like a physical link between switches. MetroE will be transparent to your L2/L3 design as you can extend these L2/L3 domains over the MetroE connection.

On your design, you need to take into account overlapping IP address assignment thus if you had a DHCP server on Site A handing out addresses and another on Site B handing out same addresses, those issues need to be corrected - same goes for static IP address assignment.

Any Network Engineer would spot this issue during the design but I believe it's worth mentioning for clarity.

__

Edison.

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