layer 2 adjacency

[bluesea2010]

Hi 

I have the below topology .Between core is layer 3 . Access layer is also layer 3 .

Now I want to connect a wlc to the core and need redundancy .

what is the solution 

question 1? what if I connect wlc also layer 3 

Thanks

[marce1000]

 - You don't need l3 for the wlc in such configurations, the core can provide the vlans usually , trunk and or with ether channel like configurations will be sufficient, 

 M.

[MHM Cisco World]

WLC is interconnect so I think It HA, 
each WLC HA have it requirement which I think need L2 connection to SW.

[Wes Schochet]

Looks like a VPC could be a good solution for you.  One for each WLC.

[Flavio Miranda]

Hello

 WLC is a layer 2 device. The way you have to connect to the core is using trunk or port-channle layer2 and you enable LAG on the wlc side if you are considereing AirOS. For IOS-XE you can setup port-channle just like you would in the core. 

 However, the wlc will have at leat the management interface with an interface vlan on the core and some dynamic interfaces if your APs were in local mode If you put them in flexconnect,  only management interface is required.

 WLC have very limited routing funcition and basically all the routing will be performed by Core.

[bluesea2010]

Hi @Flavio Miranda  @marce1000 

So i should have a l2 coonection between core , there is no other solution 

Thanks

[Flavio Miranda]

Between cores not necessarily. I meant between core and wlc.

Between cores is perfect applicable a layer3 connection with iBGP, for example.

[bluesea2010]

Hi @Flavio Miranda 

If I don't have l2 connection between the core , what will happen if  a failover happens ?

Let us say ,I  have an ssid test and vlan 10 interface on the wlc 1  and vlan 10 gateway configured on  core 1 

Thanks

[Flavio Miranda]

The WLC and Core will be connected on Layer 2. Which meanns, vlan 10 will have one interface vlan in Core 1 , lets say 10.10.10.2 amd another interface vlan on core 2, lets say 10.10.10.3.

And the wlc interface is 10.10.10.5.

Then you are going to configure HSRP on cores with VIP 10.10.10.1.

So , the gateway for wlc vlan 10 is 10.10.10.1

If Core 1 fail, the VIP will be in Core 2, thats why we use Layer2 with hrsp

This is one thing. Now, the transit vlan between Core is another thing.

If Core one fail, and lets say Core 1 and core2 have a iBGP in between, Core 2 will realize that Core 1 is no longer responding and will take over and send the traffic to the gateway and not to Core 1 anymore

[bluesea2010]

HI @Flavio Miranda 

As I understand you are advising to do the above . But HSRP works by exchanging Layer-2 messages over a shared segment 

So  the two switches need to be Layer-2 adjacent on VLAN10

Thanks

[Flavio Miranda]

Right. On you case, you have Vlan 10 on both Cores and the interconnection between then can be a trunk or port-channel and the Vlan will have interface vlan. 

The problem for HSRP would be if you created a Routed interface between the two cores. But with vlan, it should be fine. 

Create a port-channel between Cores and use another vlan to stablish the L3 communication using iBGP, for example vlan5

Allow the Vlans on the port-channel and the iBGP will be fine and HSRP will be fine. 

[bluesea2010]

Hi @Flavio Miranda 

Thanks for the reply . I got confused now .My point was how can I  stretch the vlan 10 to core 2 , since core 1 and core 2 are in different broadcast domain . what if the wlc failed which is connected to the core 1 ? , what ip address client will get  ? 

Could you please give sample configuration 

Ill try in my lab 

Thanks

[Flavio Miranda]

In a real environment,  you can use VSS or stackwise and you dont need to worry about none of it.

But , if you are going to deploy independent boxes for core, and you have two wlc in SSO, then you need a trunk extending vlan between them.

 What I say at the beginning this conversation is that the communication between cores could be in layer 2 or 3.

 Which means, you can have the trunk between then and a transit vlan for some dynamic routing protocol like iBGP or OSPF.

[MHM Cisco World]

https://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/8-7/High_Availability_DG.html

VPC can not config here don't try it. 

[bluesea2010]

Hi,

Why vpc does not work here . can you please explain 

Thanks