Controller Based WLANs

What is Router Advertisement? How to configure it? How to enable logging for it?

Aruba Employee

Introduction : In the IPv6 world, when a host comes up in network, it configures itself an link local address (derived using MAC address or other methods) and it is ready for communication in the local link scope. The next job is to find a default gateway to obtain a global address to communicate in the internet.  Hosts send multicast router solicitation to all routers’ multicast address. A router in the network would respond by a router advertisement message.
 
In order to establish continuous connectivity to the default router, the host starts the Neighbor Reachability state machine for the router. The host relies on periodic unsolicited RAs sent by the router to all hosts IPv6 multicast address.
 
A router advertisement packet contains various configurations for IPv6 hosts including the network part of the layer3 IPv6 address required by hosts to communicate in the internet. Clients then generate the universally unique host part of the address and derive the complete address.

 

Feature Notes : To enable RA there is a RA knob in each VLAN under IPv6 Neighbor discovery.


(Abilash-Lab-Cont-master-6.4) #show ipv6 ra status

IPv6 RA Status
--------------
VlanId  State     Prefix(es)
------  -----     ----------
164     disabled  None

 

Environment: Controller is the only L3 Interface in the VLAN and is expected to send out RAs in the VLAN for Address Auto configuration.

 

Network Topology : Router -------- Controller (L3) ---------------- AP ------------- Clients

 

Configuration Steps: To enable RA in a VLAN:


(Abilash-Lab-Cont-master-6.4) (config) #interface vlan 164
(Abilash-Lab-Cont-master-6.4) (config-subif)#ipv6 nd ra enable
(Abilash-Lab-Cont-master-6.4) (config-subif)#ipv6 nd ra prefix 2001::/120
(Abilash-Lab-Cont-master-6.4) (config-subif)#

 

Answer : By enabling RA in a VLAN on the controller, it will start sending out RAs ona periodic basis in the VLAN.

 

Verification : (Abilash-Lab-Cont-master-6.4) #show ipv6 ra status

IPv6 RA Status
--------------
VlanId  State    Prefix(es)
------  -----    ----------
164     enabled  2001::/120

(Abilash-Lab-Cont-master-6.4) #

 

Troubleshooting : Logging to enable for RA related debugging:

logging level debugging network process radvd
logging level debugging system process radvd

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Last update:
‎07-03-2014 08:09 PM
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