Quad DSL

Discussion in 'Cisco' started by bod43, Apr 10, 2009.

  1. bod43

    bod43 Guest

    On 10 Apr, 23:56, Darren <>
    wrote:
    > I would like to use a Cisco 2800 router with 4 x ADSL cards to load
    > share traffic to the Internet. The inside LAN would be a single /24 and
    > the router the default gateway.
    >
    > Assuming I have 4 x circuits (4 x separate public IP's), am I right in
    > assuming that subject to 4 x default routes being in the routing table,
    > the router will simply load share (using CEF) on a destination basis. I
    > would then PAT the traffic to each of the 4 public IP's.
    >
    > The only thing concerning me (subject to anyone else point out a flaw
    > int the above) is how I fail traffic over from a connection that drops
    > to one of the 3 x remaining connections.
    >
    > Normally I would use a default route pointing out the dialer interface.
    > In the event that the corresponding ATM interface goes down, the route
    > would not disappear. Working on the assumption that 4 x links may share
    > the same DSLAM I don't see how I can set a next hop address.
    >
    > Assuming a Dialer interface is the way I guess the trick is to work out
    > when the corresponding ATM went down. Alternatively use a virtual template ?
    >
    > Does anyone have an opinion on whether this is possible.


    Yes, however it is more complex than you might imagine.

    http://www.cisco.com/en/US/tech/tk648/tk361/technologies_configuration_example09186a00808d2b72.shtml
    IOS NAT Load-Balancing with Optimized Edge Routing for
    Two Internet Connections


    One other thing is that I would check very carefully that the slots
    that
    you plan to use support the WICs. I was somewhat surprised
    that on the 2801 not all slots supported the T1 WIC (maybe E1?)
    that I randomly stuck in a slot and shipped the router off. Much
    head scratching.
    bod43, Apr 10, 2009
    #1
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  2. bod43 <> writes:
    >One other thing is that I would check very carefully that the slots
    >that
    >you plan to use support the WICs. I was somewhat surprised
    >that on the 2801 not all slots supported the T1 WIC (maybe E1?)
    >that I randomly stuck in a slot and shipped the router off. Much
    >head scratching.


    THe 2801 has slot0 be a VIC only slot. The WIC-1DSU-T1-V2 should be
    able to go into any other slot than slot0. Could that be it?
    Likewise, a 2801 wouldn't be able to run 4 ADSL cards, but a 2811 and up
    should be able to.

    But I don't think the setup is going to be very easy at all unless the
    ISP supports multilink PPP on ADSL.
    Doug McIntyre, Apr 10, 2009
    #2
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  3. bod43

    bod43 Guest

    On 10 Apr, 20:07, Doug McIntyre <> wrote:
    > bod43 <> writes:


    > But I don't think the setup is going to be very easy at all unless the
    > ISP supports multilink PPP on ADSL.


    I forget the exact card now, but it was for a full voice router,
    DSPs etc. After years of pretty much, it is fits it will work,
    it was a bit of a shock:)

    I greatly applaud Cisco for making their stuff so easy to use.
    Mostly:) To those that say it is not, I recommend getting
    in a time machine, going back to 1998 and having a go
    with Cabletron, 3com, DEC, etc. No two bits of kit
    worked the same way, everything needed its own special
    console cable and magico dedicated special unique
    configuration software. I exagerate slighty perhaps.


    I should have mentioned MPPP - however I have never
    actually used an ISP that did support MPPP on DSL:-(

    The document that I listed earlier seems plausible,
    I have though not studied it in detail and as you say it is
    not exactly simple:)
    bod43, Apr 10, 2009
    #3
  4. bod43

    Darren Guest

    I would like to use a Cisco 2800 router with 4 x ADSL cards to load
    share traffic to the Internet. The inside LAN would be a single /24 and
    the router the default gateway.

    Assuming I have 4 x circuits (4 x separate public IP's), am I right in
    assuming that subject to 4 x default routes being in the routing table,
    the router will simply load share (using CEF) on a destination basis. I
    would then PAT the traffic to each of the 4 public IP's.

    The only thing concerning me (subject to anyone else point out a flaw
    int the above) is how I fail traffic over from a connection that drops
    to one of the 3 x remaining connections.

    Normally I would use a default route pointing out the dialer interface.
    In the event that the corresponding ATM interface goes down, the route
    would not disappear. Working on the assumption that 4 x links may share
    the same DSLAM I don't see how I can set a next hop address.

    Assuming a Dialer interface is the way I guess the trick is to work out
    when the corresponding ATM went down. Alternatively use a virtual template ?

    Does anyone have an opinion on whether this is possible.

    Regards

    Darren
    Darren, Apr 10, 2009
    #4
  5. bod43

    Rob Guest

    Darren <> wrote:
    > I would like to use a Cisco 2800 router with 4 x ADSL cards to load
    > share traffic to the Internet. The inside LAN would be a single /24 and
    > the router the default gateway.
    >
    > Assuming I have 4 x circuits (4 x separate public IP's), am I right in
    > assuming that subject to 4 x default routes being in the routing table,
    > the router will simply load share (using CEF) on a destination basis. I
    > would then PAT the traffic to each of the 4 public IP's.


    This is normally not going to work, because in a setup like that the
    router will send traffic randomized to the 4 circuits independent of
    the source address, and the ISP will normally (or: hopefully) filter
    the traffic to prevent address spoofing.
    What you would want is the router setting up a NAT translation entry
    one time for each session, and then sticking to the particular ADSL
    circuit for that session's traffic. The initial selection of the circuit
    should somehow be balancing the traffic, and should skip circuits that
    are inoperative.
    I have tried to do this in the past, but was not very successfull.
    I used a loopback interface with policy routing to make the router select
    an outgoing interface based on source address of the traffic, but could
    not get a "traffic distribution" system working. So I used NAT acls
    to map ranges of internal addresses to external circuits. Not good
    balancing and not handling the case of a failed ADSL line.
    It looks like the OER mechanism could do what you want.
    Other manufacturers are selling specialized routers that handle this
    case out of the box with little or no configuration.
    Rob, Apr 11, 2009
    #5
  6. bod43

    alexd Guest

    Darren wrote:

    > I would like to use a Cisco 2800 router with 4 x ADSL cards to load
    > share traffic to the Internet. The inside LAN would be a single /24 and
    > the router the default gateway.


    There are several ADSL2+ suppliers in the UK and ADSL2+ offers bonding
    natively so you don't have to worry about MLPPP. If I were you, I'd get two
    bonded circuits from one ISP and two from another and then load balance
    over them, to give yourself a bit more resilience. Obviously outbound load
    balancing is a lot easier than inbound in this kind of scenario.

    --
    <http://ale.cx/> (AIM:troffasky) ()
    11:56:49 up 129 days, 13:07, 2 users, load average: 0.09, 0.16, 0.10
    My god, said I, with my one liquid eye, am I dreaming, or am I insane?
    alexd, Apr 13, 2009
    #6
  7. bod43

    Rob Guest

    alexd <> wrote:
    > Darren wrote:
    >
    >> I would like to use a Cisco 2800 router with 4 x ADSL cards to load
    >> share traffic to the Internet. The inside LAN would be a single /24 and
    >> the router the default gateway.

    >
    > There are several ADSL2+ suppliers in the UK and ADSL2+ offers bonding
    > natively so you don't have to worry about MLPPP. If I were you, I'd get two
    > bonded circuits from one ISP and two from another and then load balance
    > over them, to give yourself a bit more resilience. Obviously outbound load
    > balancing is a lot easier than inbound in this kind of scenario.


    Outbound load balancing easy? Is there no source address filtering on
    ADSL connections in the UK?
    Rob, Apr 13, 2009
    #7
  8. bod43

    alexd Guest

    Rob wrote:

    > Outbound load balancing easy? Is there no source address filtering on
    > ADSL connections in the UK?


    I assumed he was using NAT.

    --
    <http://ale.cx/> (AIM:troffasky) ()
    19:40:23 up 130 days, 20:51, 2 users, load average: 1.76, 0.90, 0.39
    My god, said I, with my one liquid eye, am I dreaming, or am I insane?
    alexd, Apr 14, 2009
    #8
  9. bod43

    Rob Guest

    alexd <> wrote:
    > Rob wrote:
    >
    >> Outbound load balancing easy? Is there no source address filtering on
    >> ADSL connections in the UK?

    >
    > I assumed he was using NAT.


    Sure, but AFAIK the NAT and load balancing functions in Cisco routers
    are independent of eachother. So when you have 4 outgoing lines and
    4 default routes the outgoing traffic will be NATted to the 4 external
    IPs but the router will not stick to using the correct external IP on
    each line. Traffic with address of line 1 will be sent on lines 2-4
    as well. Where they will be filtered when source address filtering is
    in use.

    It looks like the Optimized Edge Routing functionality is a solution
    for that problem, but it is complex.
    There exist some purpose-built routers from other manufacturers that
    were specially developed for the "multiple Internet connections to be
    used with failover and balancing in a NAT environment" problem, where
    everything works out of the box. Of course they are less flexible than
    a Cisco.
    Rob, Apr 15, 2009
    #9
  10. bod43

    alexd Guest

    Rob wrote:

    > Sure, but AFAIK the NAT and load balancing functions in Cisco routers
    > are independent of eachother. So when you have 4 outgoing lines and
    > 4 default routes the outgoing traffic will be NATted to the 4 external
    > IPs but the router will not stick to using the correct external IP on
    > each line. Traffic with address of line 1 will be sent on lines 2-4
    > as well. Where they will be filtered when source address filtering is
    > in use.


    Bod43 posted this link elsethread:

    http://www.cisco.com/en/US/tech/tk648/tk361/technologies_configuration_example09186a00808d2b72.shtml

    In the above scenario, surely the router will set the source address
    appropriate to the interface it'll be going out of? Like you've mentioned,
    no ISP in their right mind wouldn't have source address filtering on
    traffic originating from customers DSL circuits.

    > There exist some purpose-built routers [...] where everything works out of
    > the box. Of course they are less flexible than a Cisco.


    I guess that's the tradeoff. You choose between a specialist box that's easy
    to get working, but difficult to do anything unusual with, or a generalist
    one that is a pain in the ass to get working, but can do anything you can
    program it to.

    --
    <http://ale.cx/> (AIM:troffasky) ()
    23:02:15 up 133 days, 13 min, 3 users, load average: 0.26, 0.20, 0.12
    My god, said I, with my one liquid eye, am I dreaming, or am I insane?
    alexd, Apr 16, 2009
    #10
  11. bod43

    alexd Guest

    bod43 wrote:

    > Yes, however it is more complex than you might imagine.
    >
    >

    http://www.cisco.com/en/US/tech/tk648/tk361/technologies_configuration_example09186a00808d2b72.shtml
    > IOS NAT Load-Balancing with Optimized Edge Routing for
    > Two Internet Connections


    With regards to Requirement #2, "You need to identify specific hosts that
    can be reachable through only one of the ISP connections and cannot be
    available if that ISP connection is not available".

    What's the need for specifying a host that's only reachable from via one ISP
    if the 'ip sla ...' specifies a source interface?

    --
    <http://ale.cx/> (AIM:troffasky) ()
    23:17:18 up 133 days, 28 min, 3 users, load average: 0.05, 0.11, 0.09
    My god, said I, with my one liquid eye, am I dreaming, or am I insane?
    alexd, Apr 16, 2009
    #11
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