On Wed, 2005-11-02 at 00:30, Jaison Jose wrote:
hi all
IPROUTE2 supports Multipath Routing . meaning you can have more than one
gateway , balancing traffic on more than one ext interface
however the alogrithm is based on round robin ,
you can set up multipath routing by checking the option in kernel (
Advanced Routing)
ip route add default nexthop via {IPADD1} dev {IFACE1} weight 1 \
nexthop via {IPADD2} dev {IFACE2} weight 1 \
nexthop via {IPADD3} dev {IFACE3} weight 1
change weight to prefer a particular gateway
more information http://lartc.org
regards
yunus
> Hi Dirk,
>
> In the diagram just imagine that eth1 and 2 also connected with
> 2 other routers. What I need is I want to ping from 'something' (In
> the diagram,Can be a PC) to the connected interface of our linux box.
>
> Multiple default gateways will not work as it will only check the
> first one.
>
> Could you please guide me is there any applications to make the
> diagram which you made her so that I can explain little bit more as my
> english is so weak.
>
> Regards
> Jaison.
>
> On 11/1/05, Dirk Tilger <[EMAIL PROTECTED]> wrote:
> On Tue, Nov 01, 2005 at 03:51:15AM -0800, Moeen Alinaghian
> wrote:
> > ifconfig eth0 10.0.1.10 netmask 255.255.255.0 up
> > ifconfig eth1 10.0.2.10 netmask 255.255.255.0 up
> > ifconfig eth2 10.0.3.10 netmask 255.255.255.0 up
> > route add default gw 10.0.1.1 dev eth0
> > route add default gw 10.0.2.1 dev eth1
> > route add default gw 10.0.3.1 dev eth2
> >
> > what's the result, now ?
>
> He should have three different default routes. The system will
> try to
> use the first one and only if the interface is down, it will
> try the
> second. It might be with a very modern scheduler the packets
> will be
> distributed in round-robin fashion.
>
> Routing as shown above is destination only routing. The system
> should
> have a routing table like...
>
> 10.0.1.0/24 -> eth0
> 10.0.2.0/24 -> eth1
> 10.0.3.0/24 -> eth2
>
> ...just from the ifconfig (ifconfig adds routes to interfaces
> fitting
> their destination). 'default' is a special target which should
> map to
> 0.0.0.0/0. When I issue the first routing command, I would
> expect
> something like
>
> 0.0.0.0/0 -> 10.0.1.1 via eth0
>
> The other two would add
> 0.0.0.0/0 -> 10.0.2.1 via eth1
> 0.0.0.0/0 -> 10.0.3.1 via eth2
>
> When we order the routing table as the kernel would do:
> smaller netmasks
> first, we would get:
>
> Target Bits of Netmask Gateway
> Interface
> 10.0.1.0 24 direct(ARP) eth0
> 10.0.2.0 24 direct(ARP) eth1
> 10.0.3.0 24 direct(ARP) eth2
> 0.0.0.0 0 10.0.1.1 eth0
> 0.0.0.0 0 10.0.2.1 eth1
> 0.0.0.0 0 10.0.3.1 eth2
>
> I'm a kernel and want to deliver a packet to 10.0.2.6, I go
> down the
> table and do:
> - Is (10.0.2.6 AND 255.255.255.0) == 10.0.1.0?
> --> 10.0.2.0 == 10.0.1.0?
> --> No
> - Is ((10.0.2.6 AND 255.255.255.0) == 10.0.2.0?
> --> 10.0.2.0 == 10.0.2.0?
> --> Yes
> - What is the gateway and interface? Gateway is local(ARP) via
> eth1
> - Sending ARP packet to eth1 to lookup address of network card
> for
> 10.0.2.6
> - (getting the address)
> - Sending the packet.
>
> When I do the same thing for 217.17.202.242 , then the first
> rule to hit
> is number four, because every packet would match that
> destination. This
> is why it is called the default route. As long as the
> interface is up,
> rule 5+6 will never be checked. I'm not sure, but some
> operating systems
> will even ignore 5+6 when eth0 is down, as their routing
> mechanism might
> have no concept of interfaces that are down.
>
> Dirk Tilger
> Advanced Technologies ME FZ LLC
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