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BBW
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Spanning Vlans Across WAN Links

Tue Jun 29, 2010 10:25 am

Any of you guys know the best way to span vlans over wan links?

Here’s what I’ve got. We have two networks connected via a 15-meg MPLS circuit. The switches on either side are 3560G’s. The VMware guys want to have some of the vlans on either side of the link to be accessible from the other side. In other words they want to be able to place ports in site B in a vlan that currently only resides in site A. That way if the VMware servers from site A have to come up in site B they won’t have to readdress everything.

Is this something that I can do with tunnel groups, using HSRP groups so that either switch can route traffic to that vlan? Any good documentation on how to do this?

Thanks,

Ben

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Re: Spanning Vlans Across WAN Links

Tue Jun 29, 2010 11:13 am

The only thing that comes to mind is bridging or L2TPv3 psuedo-wire. Since this is a switch to switch connection dont think its going to be possible.

Q in Q tunneling would work though.

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Re: Spanning Vlans Across WAN Links

Tue Jun 29, 2010 12:11 pm

QinQ will only work if the WAN provides the passing of ethernet frames. I'm assuming that isn't the case here. Getting a VPLS service with l2pt support would be your best bet. That would give you the "cloud as an ethernet switch" set up you need.

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Re: Spanning Vlans Across WAN Links

Tue Jun 29, 2010 7:49 pm

I opened a TAC case with Cisco about this today. I'm not sure the guy I worked with really had any experience doing it, but he seemed to agree with me that I could do it using GRE tunnels and expanding my HSRP groups for each vlan.

I'll do some testing tomorrow and let you know how I make out. I've done things like this in the past where I had to bridge flat networks across wan links, but that was always just done on the router. I've never done it with layer 3 switches like this.

Ben

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Re: Spanning Vlans Across WAN Links

Tue Jun 29, 2010 8:03 pm

BBW wrote:I opened a TAC case with Cisco about this today. I'm not sure the guy I worked with really had any experience doing it, but he seemed to agree with me that I could do it using GRE tunnels and expanding my HSRP groups for each vlan.

I'll do some testing tomorrow and let you know how I make out. I've done things like this in the past where I had to bridge flat networks across wan links, but that was always just done on the router. I've never done it with layer 3 switches like this.

Ben



I don't think that guy knows what he is talking about. How is GRE and HSRP going to allow VLANs to span the WAN? You can create the same VLAN on both sides and have overlapping addresses, but thats not the same thing as VLANs spanning across.

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Re: Spanning Vlans Across WAN Links

Tue Jun 29, 2010 8:23 pm

I think you could probably do it with GRE tunnels and AToM, but I can't quite wrap my head around it without labbing.
http://blog.alwaysthenetwork.com

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Re: Spanning Vlans Across WAN Links

Tue Jun 29, 2010 8:50 pm

I think you are right Vito, just without the GRE tunnel part. AToM can do this:
http://blog.ine.com/tag/xconnect/

Haven't read into it much but I believe there are some problems with STP and Mac address learning.

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Re: Spanning Vlans Across WAN Links

Tue Jun 29, 2010 9:27 pm

No, you're talking about the provider side, which you could obviously use AToM for.

I'm saying you could run AToM across GRE tunnels on gear he owns. Maybe with bridged ints too or something. I can't get my head around it, but if I get some time I'll try to lab a solution.
http://blog.alwaysthenetwork.com

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Re: Spanning Vlans Across WAN Links

Tue Jun 29, 2010 9:32 pm

There is something called EoIP (Ethernet over IP) that can let you do this. I don't think it has a lot of support though...

I thought I saw something else that can do this very recently... Didn't PacketPushers talk about it?

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Re: Spanning Vlans Across WAN Links

Tue Jun 29, 2010 9:44 pm

Vito_Corleone wrote:No, you're talking about the provider side, which you could obviously use AToM for.

I'm saying you could run AToM across GRE tunnels on gear he owns. Maybe with bridged ints too or something. I can't get my head around it, but if I get some time I'll try to lab a solution.


EoMPLSoGRE, I was reading about that today. I'm pretty sure 3560s don't support full MPLS though, just VRF-Lite. You'll need a Metro series switch or a router IIRC.

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Re: Spanning Vlans Across WAN Links

Tue Jun 29, 2010 9:51 pm

BBW wrote:Any of you guys know the best way to span vlans over wan links?

Here’s what I’ve got. We have two networks connected via a 15-meg MPLS circuit. The switches on either side are 3560G’s. The VMware guys want to have some of the vlans on either side of the link to be accessible from the other side. In other words they want to be able to place ports in site B in a vlan that currently only resides in site A. That way if the VMware servers from site A have to come up in site B they won’t have to readdress everything.

Is this something that I can do with tunnel groups, using HSRP groups so that either switch can route traffic to that vlan? Any good documentation on how to do this?

Thanks,

Ben


I'd recommend taking a look at the network requirements for VMotion as well. Not gonna happen on a 15mb circuit. :?

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Re: Spanning Vlans Across WAN Links

Tue Jun 29, 2010 10:21 pm

Speaking of Packet Pushers, I just listened to that very recording this morning where they talked about this but I always doze off when they talk about data centers. I'm pretty sure this was the recording which included Stretch. EoMPLSoGRE could sure use some more acrynyms in there!

Vito, can't wait to see the results of your labbing as I think this is a very interesting topic.

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Re: Spanning Vlans Across WAN Links

Tue Jun 29, 2010 10:25 pm

Infinite wrote:There is something called EoIP (Ethernet over IP) that can let you do this. I don't think it has a lot of support though...

I thought I saw something else that can do this very recently... Didn't PacketPushers talk about it?


EoIP = AToM = pseudowire = etc, so many names for it. (Edit: Actually, EoIP might mean something else, I was thinking of EoMPLS)

I think the new thing you're talking about might be OTV, which is cool too.

I finished up my lab, I'll post in a minute. It worked like I was hoping.
http://blog.alwaysthenetwork.com

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Re: Spanning Vlans Across WAN Links

Tue Jun 29, 2010 10:34 pm

Well there are EtherIP tunnels too... :)

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Re: Spanning Vlans Across WAN Links

Tue Jun 29, 2010 10:50 pm

First let me preface this by saying it won't fit this exact scenario as your 3560s likely won't support MPLS/LDP. But if you had routers at the edge you could do it.

Ok, here's the topology:

Image

R1 and R3 are owned by the customer, the PE is obviously the provider's. So I've created a GRE tunnel between R1 and R3, then I brought up LDP between them. Last I created an xconnect to run AToM/EoMPLS across the tunnel. Here's the config:

R1:
Code: Select all
interface Loopback0
 ip address 1.1.1.1 255.255.255.255
 ip ospf 100 area 0
!
interface Serial0/0
 ip address 10.1.12.1 255.255.255.0
 description To PE
!
ip route 0.0.0.0 0.0.0.0 10.1.12.2
!
mpls ldp router-id Loopback0
!
interface Tunnel13
 ip unnumbered Serial0/0
 ip ospf 100 area 0
 mpls ip
 keepalive 10 3
 tunnel source Serial0/0
 tunnel destination 10.1.23.3
!
pseudowire-class one
 encapsulation mpls
!
interface FastEthernet0/0
 no ip address
 duplex auto
 speed auto
 xconnect 3.3.3.3 100 pw-class one


R3:
Code: Select all
interface Loopback0
 ip address 3.3.3.3 255.255.255.255
 ip ospf 100 area 0
!
interface Serial0/0
 ip address 10.1.23.1 255.255.255.0
 description To PE
!
ip route 0.0.0.0 0.0.0.0 10.1.23.2
!
mpls ldp router-id Loopback0
!
interface Tunnel13
 ip unnumbered Serial0/1
 ip ospf 100 area 0
 mpls ip
 keepalive 10 3
 tunnel source Serial0/1
 tunnel destination 10.1.12.1
!
pseudowire-class one
 encapsulation mpls
!
interface FastEthernet0/0
 no ip address
 duplex auto
 speed auto
 xconnect 1.1.1.1 100 pw-class one


So basically we just create a couple tunnels across the GRE tunnel, lol. The xconnect gives us an L2 connection which spans the cloud. And it works:

Code: Select all
server-1#ping 192.168.1.20

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.20, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/9/12 ms


Shit's pretty cool.
http://blog.alwaysthenetwork.com

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Re: Spanning Vlans Across WAN Links

Tue Jun 29, 2010 11:01 pm

that is pretty awesome!

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Re: Spanning Vlans Across WAN Links

Tue Jun 29, 2010 11:08 pm

auglan wrote:The only thing that comes to mind is bridging or L2TPv3 psuedo-wire.


I'd say this is the most direct route. Though you can't do it on the 3500 platform; if you have a spare port on the routers they're connected to you could use them as pseudowire interfaces. It should work, although I've only tried such a setup in the lab. I need to fire the lab back up and test with the DF bit set, but you could run into issues depending what you and your provider's MTUs are set at.

Vito, any advantages to doing EoMPLSoGRE vs L2tpv3?

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Re: Spanning Vlans Across WAN Links

Tue Jun 29, 2010 11:11 pm

Never used L2TP before, really no idea how it works.:(
http://blog.alwaysthenetwork.com

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Re: Spanning Vlans Across WAN Links

Tue Jun 29, 2010 11:22 pm

That is where the 'mpls mtu' command comes in handy.

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Re: Spanning Vlans Across WAN Links

Tue Jun 29, 2010 11:29 pm

Looks like L2TP is a bit easier. That's not supported on 3560s either though. :|
http://blog.alwaysthenetwork.com

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