RE: [load balancing] Alteon mult. gatways

From: Peter Degrassi (
Date: Wed Sep 18 2002 - 23:04:53 EDT

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    Hi Jon,
    Ken is correct. To re-state, when VMA is enabled, DAM or not, all
    processing is done on the designated processor. This allows WebOS to
    perform processing in the following order, Server, Filter, Client, depending
    on ingress port settings.
    With VMA disabled and DAM enabled Server processing takes place AFTER Filter
    processing. Why? Because the session table lookup occurs AFTER filter
    processing, AFTER the frame is forwarded to the egress port.
    With both VMA and DAM disabled, there is no session table lookup. Server
    processing happens regardless , if configured and SIP=RIP and SPORT=RPORT,
    on the ingress port. Then Filter, then Client, if configured.
    Prior to the introduction to VMA (with 8.0 in May 2000), FWLB+SLB+DAM were
    not easy to do. The problem being the re-direction filter would fire before
    the RIP to VIP (unNAT) opening up the possibility of assymetrical flow
    through the FW sandwich. VMA solved all that, refer to my first paragraph.
    Regards... Peter

    -----Original Message-----
    From: []
    Sent: Wednesday, September 18, 2002 5:01 PM
    Subject: RE: [load balancing] Alteon mult. gatways

    While the alteon will move the server-side processing to the client ASIC,
    that doesn't mean that that physical port is required to be the egress point
    for the un-NATing to occur. If that were true, then the server-side
    processing would be configured on the client-side port. That being the case
    (to the best of my knowledge it is) VMA shouldn't be required. The
    server-side processing will still occur on the same physical
    (ingress/server-side) port; DAM simply gives it the intellegence to check
    the session table to find out if it should really change the source back to
    the VIP. That all occurs before the filter process, so VMA shouldn't be

    Having said that, I'd like to also mention that this is all based around my
    understanding of the Alteon's logic. I'll gladly defer to those with a more
    in depth knowledge of the product.


               Jon Hartman
     Network Engineering
     Verizon Internet Operations

     Cell: 214-513-6792

            "Kenneth Thurman" <>
    Sent by:

    09/16/2002 01:23 PM
    Please respond to lb-l

            To: "''" <>
            Subject: RE: [load balancing] Alteon mult. gatways

      With DAM enabled Server processing happens on Client port, with VMA
    disabled Client processing will happen on the Physical ingress port, and
    when the server replies the translation from RIP to VIP will not happen
    until it egresses on the Client port. SO if you have a filter to redirect
    server replies based on VIP you won't see the VIP as the source IP on the
    server port, as server processing hasn't happened yet. BUT with VMA both
    client and server will happen on the same port, which will probalby not be
    the phyiscal port for either the server or the client connection. So you can
    put in a filter that looks for VIP replies back to client and redirect them
    to the correct gateway.
    Does that answer the question?
    -----Original Message-----
    From: []
    Sent: Monday, September 16, 2002 11:32 AM
    Subject: RE: [load balancing] Alteon mult. gatways


    Could you please expand a bit on why VMA would be required if DAM is


               Jon Hartman
    Network Engineering
    Verizon Internet Operations

    Cell: 214-513-6792

            "Kenneth Thurman" <>
    Sent by:

    09/12/2002 09:05 AM
    Please respond to lb-l

           To: "''" <>
           Subject: RE: [load balancing] Alteon mult. gatways


      What you can do is the following;

    1) create 2 reals, 1 being the ISP1 router, other being ISP2 router.

    2) put the reals in separate groups;

    3) Create redirect filters, with the following Criteria;
      SIP = smask = action redirect group = ISP1
    Router group.
      SIP = smask = action redirect group = ISP2
    Router group.
    4) Apply filters to server ports.

    This should work, as server processing will happen before filter processing.
    If DAM is enabled then VMA must be enabled for this to work.


    Ken T.

    -----Original Message-----
    From: Jay Kline [ <>]
    Sent: Wednesday, September 11, 2002 8:13 PM
    Subject: [load balancing] Alteon mult. gatways

    I have an alteon 180e running webos 10, and need to get multiple gateways
    up. Here is what we want:

    port 8 -> direct connection to ISP1
    port 7 -> direct connection to ISP2

    We have a web server load balanced (private IP space) running on port 1, and

    will have a virtual IP on both ISP1's network, and ISP2's network (ie, vip and vip We have not set this up yet, so I do not
    know the behavior with multiple default gateways. I have port 1 on VLAN1,
    port 7 on VLAN7 and port 8 on VLAN8. I currently have a default gateway set
    up for ISP1, with the vip on that network, and all is fine. As of tommrow,
    will get a our second connection in. If I add a second default gateway, does

    the Alton know which to use (based off which interface/vlan/network it came
    from)? Is there some way of specifying this? The doc's vaguely mention
    multiple gateways, and apparently only 184's can do gateways based on VLANs.

    Any advice?


    Jay Kline 
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