Cisco 6504-E VSS and WLC 5508 Integration

[mohankumarm]

Hello,

We have implemented VSS on Cisco 6504-E switches using the 10GE links on the Sup-720-10GE. Two Cisco WLC 5508 controllers are planned to be connected in a LAG configuration, (consisting of eight links per LAG bundle) to each of the  6504-E chassis( Total of four WLC, two for the primary location and two for secondary location). WLC HA feature may be implemented on the primary and secondary WLC controllers using the 7.3 latest code release.

In this scenario, i would like to seek clarification on some of the design /configuration requirements  on the 6504E switches:

1. VLAN 100 - 200 is configured for the Active Primary 6504-E switch and VLAN 200-300 for the Standby 6504-E switch. The IP scopes for the VLAN are defined in the 172.16.x.x range on the Primary and 172.17.x.x on the secondary. As there no cross links(Multichassis LAG) from the WLC controllers to the 6504-E switches, is it better off implementing a single common VLAN range on a single subnet block for the VSS, which in the event of say Primary switch failure, the Wireless APs do not have to re-associate with a different IP range on the secondary? What is the best design practise in this case?

2. What is the best practise for implementing a single management loopback address for the VSS domain-  is this implemented using a port channel (Layer 3 MEC) as below?  and is the loopback IP address on a totally different IP range reference to point 1 above?

Can the VLAN IP ranges on the 6504-E VSS be assigned in two different subnets say 172.16/12(100-200) and 17.17/12(300-400) and  the common loopback (lo0) in 172.18.x.x/32 or is it better to have one common 172.16/12 subnet spanning the entire VLAN range (100-400). Cisco documentation describes creating port channels from the line card card physical ports as opposed to just creating lo0 and advertising this into the IGP.

int g1/x/1

desc VSS Management

channel-group mode 101 active

int gi2/x/1

channel-group mode 101 active

int po101

desc VSS Management

ip ad 172.18.x.x/32

Thanks and Regards,

Mohan

[Reza Sharifi · Accepted solution]

Hi,

For question number 1, I agree with a single subnet block, as the vss pair logically is one switch and you don't need multiple subnets.

For question number 2, if you want to use a loopback interface, than that is an in band management and you assign a /32 (host) address to it and added to your IGP to get routed. You usually want to use a separate subnets for all your loopback interfaces in your network. If you are using a physical interface for managment, you don't need a portchannel.  A single physical interface is good enough.

Also as in your example, you can't assign a /32 subnet to vlan interface or physical interface.  You can only assign a /32 (host) address to a loopback interface.

HTH 

[mohankumarm]

Hi Reza,

Thanks very much indeed and will assign a single subnet block for the VSS pair and assign a separate /32 address for the loopback and add it to the IGP.

Thanks and Regards.