Flexconnect and Broadcasts

[wscotty2012]

Hi All,

I'm planning on configuring flexconnect for 25 access points and I want to check what affect broadcasts will have from the local area network connecting to the Flexconnect APs. I will have a /23 network configured on VLAN 10 which will be tagged to all of the flexconnect APs. If there is a high level of broadcasts in VLAN 10 will all APs hear them and attempt to forward out of the radio interfaces?

Thank you                  

[Stephen Rodriguez]

The AP will have to process any broadcast traffic that is trimmed to it, but I believe that it will not be transmitted to the clients.

Steve

Sent from Cisco Technical Support iPhone App

[Saravanan Lakshmanan]

Flex local switching broadcasts are, or should be, strictly forwarded between the SSID and the VLAN, Whether it is wireless to wireless or wired to wireless. The way it work is, Broadcast from Client to AP is sent as 802.11 unicast, while AP to Client it'll be sent as 802.11 Broadcast. Wired side principle applicable once broadcast hit the wired vlan.

Difference is, AP on local mode/central switching does proxy arp for arp requests for clients while not on hreap locally switched WLAN(may be it is supported in the future). Proxy arp is supported on IOS AP.

On WLC using local mode, we can enable/disable broadcast forwarding and can't block AP to Client(s) broadcasts on hreap local switching. If you prefer to block AP to Client broadcast then enable GTK randomize for WPA encryption. Remember it breaks the broadcast(& multicast), so does the arp for wireless clients and not for wired side clients.

DHCP proxy can't be configured or NA for hreap.

Note: More downlink broadcasts cause high channel utilization.

[nwittenberg]

I am having a hard time interperting your response here Saravanan.

With APs in FC mode and local switching how are broadcast such as ARPs handled coming from the wired network?  Does the AP proxy for the client or does the ARP get sent out on the wireless on every AP attached on that VLAN?

Similar, with multicast such as Bonjour on the same VLAN, will the AP only send the stream to the client (and via which method, mc or uc) due to igmp snooping or does the multicast just get sent out the wireless?

Basically I am trying to understand the limitations of FC w/local switching (if any) as I have a customer who wants to deploy up to 100 APs at a facility.

This is what I have come up with so far:

• Limitations
  • No AVC Support
  • Bonjour Services are limited to the local vlan (no bonjour gateway)
  • Spanning Vlans across  closets is necessary for roaming

[Nicolas Escudero]

Hello saravlak ,

Great information! do you have any official link/doc to share that supports your statements above regarding how broadcasts propagate each way for the different scenarios (FlexConnect central/Local switching and Local Mode). I know by life experience it works the way you mention, but need to provide some offcial documentation to my customer and was having a very hard time finding somthing solid.

Thanks in Advance!