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epaalx's avatar
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Sep 19, 2011

multiple interfaces on a single VLAN

Hello F5'ers,


I've taken it for granted that it just works, but was questioned by a non-F5 colleague and couldn't provide qualified answer or cite documentation....


"TMOS Management Guide for BIG-IP Systems", Chapter 7, section "Related configuration tasks":


"When you assign multiple interfaces to a single VLAN, traffic destined for a host in that VLAN can travel through any one of these interfaces to reach its destination"


Questions (assuming STP hadn't blocked all):


1. How is outgoing traffic distributed - would ARPs be sent out on both interfaces?


2. How is returning traffic distributed (towards Clients) when AutoLasthop is disabled?


3. If a multicast/broadcast arrives on one interface, would F5 forward it onto second interface?




2 Replies

  • Hi Epaalx,


    I think the following link might answer your questions regarding how trunk links forwarding packets are distributed




    AS for multicast the following link might be helpful




    I hope this helps


  • Hi Bhattman,


    thanks, but my issue isn't with Trunks - LTM allows multiple Interfaces (multiple Trunks, too) associated with a VLAN.. The question is - how does TMM distribute outgoing traffic among the Interfaces (and Trunks)?



    Re: "3. If a multicast/broadcast arrives on one interface, would F5 forward it onto second interface?" - I think I can answer this myself - as per F5 SOL9310: "By default, LTM functions as an L2-only switch, flooding frames addressed to L2 multicast addresses across all interfaces in the VLAN but the origin." Since broadcast is a general type of multicast, then for both cases, LTM will forward them onto other interfaces.



    R's, Alex