Re: [load balancing] BigIP's and trunking

From: John Hall (
Date: Wed Jan 16 2002 - 22:41:16 EST

  • Next message: Rick Masters: "RE: [load balancing] BigIP's and trunking"

    Trunking is unfortunately an over-used word, causing much confusion
    in the world today... :(

    Your reference to 802.1q leads me to believe you are talking about the
    trunks that are defined 802.1q Annex D where you have multiple tagged
    VLAN's configured on a single interface in order to pass traffic for
    multiple VLAN's between two switches. All BIG-IP versions after v3.1
    support tagged VLAN's (although I have to admit the support got *MUCH*
    better after v4.x) and assigning multiple VLAN's to a single interface
    for the purpose of VLAN trunking (that's what *I* call this use).
    Although I'm confused by your reference to "bandwidth aggregation".

    Rick has already replied to you referring to our "bigpipe trunk"
    command, which is used to configure 802.1ad Link Aggregations, which
    are used to make multiple links (physical ports) operate as a single
    interface providing the sum of the bandwidths of the aggregated links
    to the interface and also providing link failure protection (if one
    of several aggregated links goes down, the others continue to operate).
    One practical note is that, like most 802.1ad implementations, ours
    works most efficiently if the number of interfaces configured is a
    multiple of two. Another quirk of 802.1ad that is often not known
    is that all packets associated with a single IP connection (say a
    single telnet session) are *always* sent on the same link of an
    aggregation (this is required by the spec). So, if you setup a
    link aggregation, using 4 100BaseTX ports, and try to download a
    single huge file via FTP, that single download will only be allowed
    approximately 100Mb/s of bandwidth, but if you have a bunch of sessions
    going simultaneously, you will see all four links utilized.

    Before you ask, yes, you can configure a single set of links (say four
    100BaseTX ports) to operate as an 802.1ad link aggregation (giving you
    close to 400Mb/s of bandwidth on the interface) with multiple tagged
    VLAN's going across that interface to another switch. One of our test
    configurations uses four gigabit interfaces aggregated to a single
    interface over which we pass traffic from four (two internal and two
    external) VLAN's and it works like a charm. Link aggregation allows
    you to use the full bandwidth capacity of your BIG-IP in a balanced
    way when your traffic load is asymmetric (such as with web traffic
    where the incoming requests are small, but the responses are large).

    Hope this helps,

    Tim Maestas wrote:
    > I was wondering if anyone has had any experiences (good, bad, or
    > otherwise) with using trunking under BigIP 4.x, in particular into a Cisco
    > 6500 series switch. In reading the 4.x documentation, there is no mention
    > of 802.1q trunk modes like there was in 3.x, so I'm not sure how I would
    > be able to make my Cisco treat my trunked interfaces as a group. In 4.x
    > it seems like outgoing packets from the BigIP would be
    > "load-balanced" between the interfaces, but I don't see how this is
    > possible for incoming packets, without something like 802.1q. Granted,
    > if nothing else trunks will give me interface failover, but I'm looking
    > more for bandwidth aggregation. Any info would be appreciated.
    > -Tim
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