BGP Load Sharing

Discussion in 'Cisco' started by jcle, Aug 19, 2010.

  1. jcle

    jcle Guest

    Can someone give me a good generic way to load share BGP outbound. I
    have three connections a 40Mb/s; 20Mb/s; and a 20Mb/s connection.
    This is currently being done thought PBR. I have a /21 of internet
    ips and PBR says if you are in a certain /24 go out this connection.
    This does a good job sharing the outbound load but creates problems
    when we have a ISP failure.

    On all three connections I am taking a partail table + default.
    Thanks.

    BTW I am hoping to spawn a big discussion with this one..
     
    jcle, Aug 19, 2010
    #1
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  2. jcle

    bod43 Guest

    On 20 Aug, 03:54, "John Agosta" <> wrote:
    > Are your three connections to a single ISP, or different ISPs?
    > If a single ISP, you can use "maximum paths."
    >
    > "jcle" <> wrote in message
    >
    > news:...
    >
    > > Can someone give me a good generic way to load share BGP outbound.  I
    > > have three connections a 40Mb/s; 20Mb/s; and a 20Mb/s connection.
    > > This is currently being done thought PBR.  I have a /21 of internet
    > > ips and PBR says if you are in a certain /24 go out this connection.
    > > This does a good job sharing the outbound load but creates problems
    > > when we have a ISP failure.

    >
    > > On all three connections I am taking a partail table + default.
    > > Thanks.

    >
    > > BTW I am hoping to spawn a big discussion with this one..


    I am not against discussions, however I don't
    much fancy load sharing - ever really.

    The problem with it is that when load sharing is
    used failures can be *much* more difficult to
    deal with.

    Even the simplest case where say per packet
    load sharing is done through two outbound
    connections. If one connection suddenly goes bad and
    generates a 50% packet loss rate users will experience
    a 25% loss but it may well be difficult to
    figure out what is going on. What tools will you use to
    figure out which connection is bad?

    Also remember that even when load sharing
    you can only influence outbound traffic - unless
    of course you use NAT after the load sharing point
    which is yet another layer of potential troubleshooting
    nightmare.

    The correct answer when management says "Surely
    we can get something out of that expensive second
    circuit? Leaving it idle all of the time is making my
    head hurt." is to explain the the alternative is to have
    a less reliable network that is harder or even impossible
    to fix.

    Just remember to make sure that the second path is
    regularly tested, preferrably with automatic tools.
     
    bod43, Aug 20, 2010
    #2
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  3. jcle

    jcle Guest

    On Aug 20, 4:14 am, bod43 <> wrote:
    > On 20 Aug, 03:54, "John Agosta" <> wrote:
    >
    >
    >
    >
    >
    > > Are your three connections to a single ISP, or different ISPs?
    > > If a single ISP, you can use "maximum paths."

    >
    > > "jcle" <> wrote in message

    >
    > >news:...

    >
    > > > Can someone give me a good generic way to load share BGP outbound.  I
    > > > have three connections a 40Mb/s; 20Mb/s; and a 20Mb/s connection.
    > > > This is currently being done thought PBR.  I have a /21 of internet
    > > > ips and PBR says if you are in a certain /24 go out this connection.
    > > > This does a good job sharing the outbound load but creates problems
    > > > when we have a ISP failure.

    >
    > > > On all three connections I am taking a partail table + default.
    > > > Thanks.

    >
    > > > BTW I am hoping to spawn a big discussion with this one..

    >
    > I am not against discussions, however I don't
    > much fancy load sharing - ever really.
    >
    > The problem with it is that when load sharing is
    > used failures can be *much* more difficult to
    > deal with.
    >
    > Even the simplest case where say per packet
    > load sharing is done through two outbound
    > connections. If one connection suddenly goes bad and
    > generates a 50% packet loss rate users will experience
    > a 25% loss but it may well be difficult to
    > figure out what is going on. What tools will you use to
    > figure out which connection is bad?
    >
    > Also remember that even when load sharing
    > you can only influence outbound traffic - unless
    > of course you use NAT after the load sharing point
    > which is yet another layer of potential troubleshooting
    > nightmare.
    >
    > The correct answer when management says "Surely
    > we can get something out of that expensive second
    > circuit? Leaving it idle all of the time is making my
    > head hurt." is to explain the the alternative is to have
    > a less reliable network that is harder or even impossible
    > to fix.
    >
    > Just remember to make sure that the second path is
    > regularly tested, preferrably with automatic tools.- Hide quoted text -
    >
    > - Show quoted text -


    Thanks for the input
    The three different ISPs so peering loopbacks ebgp multihop with per
    packet is not an option.

    The problem is that this is non profit with no budget..

    If I pull off PBR which should be pulled off b/c it creates a routing
    loop when an isp goes down. We will be over CIR on any of the three
    connections.
     
    jcle, Aug 20, 2010
    #3
  4. jcle

    Stephen Guest

    On Thu, 19 Aug 2010 12:48:11 -0700 (PDT), jcle <>
    wrote:

    >Can someone give me a good generic way to load share BGP outbound. I
    >have three connections a 40Mb/s; 20Mb/s; and a 20Mb/s connection.
    >This is currently being done thought PBR. I have a /21 of internet
    >ips and PBR says if you are in a certain /24 go out this connection.
    >This does a good job sharing the outbound load but creates problems
    >when we have a ISP failure.
    >
    >On all three connections I am taking a partail table + default.
    >Thanks.
    >

    if you take a partial feed from each then you should already be
    automatically sending traffic to each ISP for their AS - they should
    be sending routes for anything local to them.

    So the PBR should only be handling "other" stuff that doesnt go into
    your routing table?

    maybe you need more than a partial BGP feed on at least some of the
    pipes so you can split by destination for other ASes?

    a cisco article that may help:
    http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a00800945bf.shtml

    >BTW I am hoping to spawn a big discussion with this one..

    --
    Regards

    - replace xyz with ntl
     
    Stephen, Aug 22, 2010
    #4
  5. jcle

    jcle Guest

    On Aug 22, 10:14 am, Stephen <> wrote:
    > On Thu, 19 Aug 2010 12:48:11 -0700 (PDT), jcle <>
    > wrote:
    >
    > >Can someone give me a good generic way to load share BGP outbound.  I
    > >have three connections a 40Mb/s; 20Mb/s; and a 20Mb/s connection.
    > >This is currently being done thought PBR.  I have a /21 of internet
    > >ips and PBR says if you are in a certain /24 go out this connection.
    > >This does a good job sharing the outbound load but creates problems
    > >when we have a ISP failure.

    >
    > >On all three connections I am taking a partail table + default.
    > >Thanks.

    >
    > if you take a partial feed from each then you should already be
    > automatically sending traffic to each ISP for their AS - they should
    > be sending routes for anything local to them.
    >
    > So the PBR should only be handling "other" stuff that doesnt go into
    > your routing table?
    >
    > maybe you need more than a partial BGP feed on at least some of the
    > pipes so you can split by destination for other ASes?
    >
    > a cisco article that may help:http://www.cisco.com/en/US/tech/tk365/technologies_configuration_exam...
    >
    > >BTW I am hoping to spawn a big discussion with this one..

    >
    > --
    > Regards
    >
    > - replace xyz with ntl


    Stephen thanks for the input. The problem is that the providers are
    tier 3 so I don't see a whole lot of connectivity to other customers
    of the providers, otherwise getting provider generated routes would be
    the way to go. I think I am just going to have to get a full table
    from all providers and match different attributes with netflow reports
    to get it to work correctly.

    The current PBR solution is legacy to me tenure. There are two edge
    routers in this senerio. They are tied with HSRP on the inside ip
    space. All traffic hits the master and there is a PBR statement on
    that interface that says if you are coming from this source IP set
    next hop to this ISP. The problem is if that ISP goes down PBR sends
    it there and that router gets a defualt route back at the hsrp master.
    So we get a routing loop. BGP can't really do its job. It works fine
    and dandy if all ISPs are up.
     
    jcle, Aug 25, 2010
    #5
  6. jcle

    Alael Guest

    Hi there,

    Might it be easier to ask the ISPs to send you the routes?

    Maybe you could negotiate that if the links are a bit old, and for the same
    price maybe you could get a upgrade? (I recently added 20Mbit for the same
    price on a 2 year old link that still has 1 year to go... ;) ).

    That way you could share it with the routes from the ISP and fine tune it a
    bit...

    Route maps (the link from Cisco someone posted has some nice tips on
    that...) may be a good choice too.

    Oh, and check the local AND remote ISP IP address for your link for
    monitoring purposes... it's a pain when one of your links goes down and you
    reach the remote ISP route through THE OTHER active link... ;)

    Cheers,
    Nuno

    "jcle" <> wrote in message
    news:...
    > On Aug 22, 10:14 am, Stephen <> wrote:
    >> On Thu, 19 Aug 2010 12:48:11 -0700 (PDT), jcle <>
    >> wrote:
    >>
    >> >Can someone give me a good generic way to load share BGP outbound. I
    >> >have three connections a 40Mb/s; 20Mb/s; and a 20Mb/s connection.
    >> >This is currently being done thought PBR. I have a /21 of internet
    >> >ips and PBR says if you are in a certain /24 go out this connection.
    >> >This does a good job sharing the outbound load but creates problems
    >> >when we have a ISP failure.

    >>
    >> >On all three connections I am taking a partail table + default.
    >> >Thanks.

    >>
    >> if you take a partial feed from each then you should already be
    >> automatically sending traffic to each ISP for their AS - they should
    >> be sending routes for anything local to them.
    >>
    >> So the PBR should only be handling "other" stuff that doesnt go into
    >> your routing table?
    >>
    >> maybe you need more than a partial BGP feed on at least some of the
    >> pipes so you can split by destination for other ASes?
    >>
    >> a cisco article that may
    >> help:http://www.cisco.com/en/US/tech/tk365/technologies_configuration_exam...
    >>
    >> >BTW I am hoping to spawn a big discussion with this one..

    >>
    >> --
    >> Regards
    >>
    >> - replace xyz with ntl

    >
    > Stephen thanks for the input. The problem is that the providers are
    > tier 3 so I don't see a whole lot of connectivity to other customers
    > of the providers, otherwise getting provider generated routes would be
    > the way to go. I think I am just going to have to get a full table
    > from all providers and match different attributes with netflow reports
    > to get it to work correctly.
    >
    > The current PBR solution is legacy to me tenure. There are two edge
    > routers in this senerio. They are tied with HSRP on the inside ip
    > space. All traffic hits the master and there is a PBR statement on
    > that interface that says if you are coming from this source IP set
    > next hop to this ISP. The problem is if that ISP goes down PBR sends
    > it there and that router gets a defualt route back at the hsrp master.
    > So we get a routing loop. BGP can't really do its job. It works fine
    > and dandy if all ISPs are up.
     
    Alael, Aug 26, 2010
    #6
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