[LARTC] Will advanced linux routing help me

[LARTC] Will advanced linux routing help me

[Sushil Suresh]

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Hi,

    I have a private network which is connected to 3 diffrent ISPs. I also have a linux box acting as a gateway and internet firewall for the internal network. The network is as shown below


          Linux Gateway/Firewall
                      |                
                      |
                      |
              Ethernet Hub ----------------------------------------------------------------------Ethernet Hub--------|--
             /        |           \                                                                                                |--   Local Network
          /           |             \                                                                                              |--
       /              |                \
ISP-I            ISP-II            ISP-III

 
My problem is i have a couple of sites which are to be divided into 3 groups and each to be routed through a particular isp ( this is generally choosen by the requirements of the site. Some of the sites need very fast
response time, some need large volumes of data to be transfered, and some need a very stable connection ).

Appart from these few sites the rest of the traffic is routed through one of the isp ( the one with the highest bandwidth ) 

And when a particular ISP fails the routes currently being used by this ISP is to be shifted to the other 2 ISPs.

I also require the routes to be restord back to as decided earlier once the isp which was down comes back
 
Is there any means to automise the whole process. The effective aim is to utilize the most of all the isps that are available at a moment of time.

( At the moment we attain this via static routing and we have one personal monitoring this round the clock, in case a rerouting is necessary )


with regards,
Sushil Suresh

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Re: [LARTC] Will advanced linux routing help me

[Arthur van Leeuwen]

On Wed, 25 Apr 2001, Sushil Suresh wrote:

[snip, automatic rerouting when interfaces are downed]

> Is there any means to automise the whole process. The effective aim
> is to utilize the most of all the isps that are available at a moment
> of time.

> ( At the moment we attain this via static routing and we have one
> personal monitoring this round the clock, in case a rerouting is necessary )

Okay, the thing to do is to figure out what this person is doing to check if
the links are up. Once you know this, you put that knowledge into a script
that checks if the link is up and run that script from cron. Depending on
the status of the uplinks you then let the script select one of the possible
static routings and enable it. (Rebuilding routing tables barely hurts
reliability, *especially* if you do not flush the route cache).

Hope this helps.

Doei, Arthur. (The tricky part is the link-state monitoring... at the TCP/IP
               level this is theoretically impossible...)

-- 
  /\    / |      arthurvl@sci.kun.nl      | Work like you don't need the money
 /__\  /  | A friend is someone with whom | Love like you have never been hurt
/    \/__ | you can dare to be yourself   | Dance like there's nobody watching


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Re: [LARTC] Will advanced linux routing help me

[Ramin Alidousti]

On Wed, Apr 25, 2001 at 09:39:27AM +0200, Arthur van Leeuwen wrote:

> Doei, Arthur. (The tricky part is the link-state monitoring... at the TCP/IP
>                level this is theoretically impossible...)

Yes, indeed. There is no special protocol for this. That's why OSPF and
his younger and older brothers have those HELO packets. That's why TCP
has the optional keepalive segments (although, in case of TCP it's an
end-to-end behaviour).

If you know the IP of the next hop router and if that router has not been
instructed to ignore ICMP requests, ping might help. If you don't know
the IP, pinging to the subnet broadcast will also do.

Ramin

> 
> -- 
>   /\    / |      arthurvl@sci.kun.nl      | Work like you don't need the money
>  /__\  /  | A friend is someone with whom | Love like you have never been hurt
> /    \/__ | you can dare to be yourself   | Dance like there's nobody watching
> 
> 
> _______________________________________________
> LARTC mailing list / LARTC@mailman.ds9a.nl
> http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://ds9a.nl/2.4Routing/

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Re: [LARTC] Will advanced linux routing help me

[Sushil Suresh]

Hi,

    OSFP is a dynamic routing protocol, isn't it. So is dynamic routing
going to solve my problem.

The problem is i do not want to use the best possible path ( cost vise ) to
route a packet. I have to make use of all the availabe bandwitdh of the 3
ISP's in the most efficient manner.

I have read about TEQ traffic equalizer. But it has been mentioned that you
cannot combine 3 different isps to act as one.
As if you are using TEQ at one end, you are bound to have it at the other
end.

with regards,
Sushil Suresh


----- Original Message -----
From: Ramin Alidousti <ramin@UU.NET>
To: Arthur van Leeuwen <arthurvl@sci.kun.nl>
Cc: Sushil Suresh <sushil@svw.com>; <lartc@mailman.ds9a.nl>
Sent: Wednesday, April 25, 2001 6:20 PM
Subject: Re: [LARTC] Will advanced linux routing help me


> On Wed, Apr 25, 2001 at 09:39:27AM +0200, Arthur van Leeuwen wrote:
>
> > Doei, Arthur. (The tricky part is the link-state monitoring... at the
TCP/IP
> >                level this is theoretically impossible...)
>
> Yes, indeed. There is no special protocol for this. That's why OSPF and
> his younger and older brothers have those HELO packets. That's why TCP
> has the optional keepalive segments (although, in case of TCP it's an
> end-to-end behaviour).
>
> If you know the IP of the next hop router and if that router has not been
> instructed to ignore ICMP requests, ping might help. If you don't know
> the IP, pinging to the subnet broadcast will also do.
>
> Ramin
>
> >
> > --
> >   /\    / |      arthurvl@sci.kun.nl      | Work like you don't need the
money
> >  /__\  /  | A friend is someone with whom | Love like you have never
been hurt
> > /    \/__ | you can dare to be yourself   | Dance like there's nobody
watching
> >
> >
> > _______________________________________________
> > LARTC mailing list / LARTC@mailman.ds9a.nl
> > http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO:
http://ds9a.nl/2.4Routing/
>


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Re: [LARTC] Will advanced linux routing help me

[Sushil Suresh]

Hi,

    At the moment we are using trace and ping to check the availability of a
particular site, and the status of a particular ISP

The problem faced in making use of these commands in a script is that, they
may fail in case of congestion and may be misunderstood as failure of a
particular ISP.

Also how and why do you flush the route cache?

with regards,
Sushil Suresh

----- Original Message -----
From: Arthur van Leeuwen <arthurvl@sci.kun.nl>
To: Sushil Suresh <sushil@svw.com>
Cc: <lartc@mailman.ds9a.nl>
Sent: Wednesday, April 25, 2001 1:09 PM
Subject: Re: [LARTC] Will advanced linux routing help me


> On Wed, 25 Apr 2001, Sushil Suresh wrote:
>
> [snip, automatic rerouting when interfaces are downed]
>
> > Is there any means to automise the whole process. The effective aim
> > is to utilize the most of all the isps that are available at a moment
> > of time.
>
> > ( At the moment we attain this via static routing and we have one
> > personal monitoring this round the clock, in case a rerouting is
necessary )
>
> Okay, the thing to do is to figure out what this person is doing to check
if
> the links are up. Once you know this, you put that knowledge into a script
> that checks if the link is up and run that script from cron. Depending on
> the status of the uplinks you then let the script select one of the
possible
> static routings and enable it. (Rebuilding routing tables barely hurts
> reliability, *especially* if you do not flush the route cache).
>
> Hope this helps.
>
> Doei, Arthur. (The tricky part is the link-state monitoring... at the
TCP/IP
>                level this is theoretically impossible...)
>
> --
>   /\    / |      arthurvl@sci.kun.nl      | Work like you don't need the
money
>  /__\  /  | A friend is someone with whom | Love like you have never been
hurt
> /    \/__ | you can dare to be yourself   | Dance like there's nobody
watching
>


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http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://ds9a.nl/2.4Routing/

Re: [LARTC] Will advanced linux routing help me

[Arthur van Leeuwen]

On Fri, 27 Apr 2001, Sushil Suresh wrote:

>     At the moment we are using trace and ping to check the availability of a
> particular site, and the status of a particular ISP

Yes, that is the only thing you can do.

> The problem faced in making use of these commands in a script is that, they
> may fail in case of congestion and may be misunderstood as failure of a
> particular ISP.

Unfortunately, this cannot be helped, unless you have some layer-2
indication of the link still being up (something like carrier detect on
modems). This is not usually the case, however.

> Also how and why do you flush the route cache?

The why is trivial: to make sure the routing code starts off with a clean
slate and you're not surprised by routes you think you have deleted.

The how is equally simple: ip route flush table cache

Doei, Arthur.

-- 
  /\    / |      arthurvl@sci.kun.nl      | Work like you don't need the money
 /__\  /  | A friend is someone with whom | Love like you have never been hurt
/    \/__ | you can dare to be yourself   | Dance like there's nobody watching


_______________________________________________
LARTC mailing list / LARTC@mailman.ds9a.nl
http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://ds9a.nl/2.4Routing/

Re: [LARTC] Will advanced linux routing help me

[Ramin Alidousti]

On Fri, Apr 27, 2001 at 04:07:36PM +0530, Sushil Suresh wrote:

> Hi,
> 
>     At the moment we are using trace and ping to check the availability of a
> particular site, and the status of a particular ISP
> 
> The problem faced in making use of these commands in a script is that, they
> may fail in case of congestion and may be misunderstood as failure of a
> particular ISP.

Your script should not rely on only one missed ping. You should add
some intelligence to the script.

BTW, what do you do with trace?

> 
> Also how and why do you flush the route cache?

Arthur covered this just fine ;-)

Ramin

> 
> with regards,
> Sushil Suresh

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Re: [LARTC] Will advanced linux routing help me

[Ramin Alidousti]

On Fri, Apr 27, 2001 at 03:59:49PM +0530, Sushil Suresh wrote:

> Hi,
> 
>     OSFP is a dynamic routing protocol, isn't it. So is dynamic routing
> going to solve my problem.

No. You cannot run a routing protocol on your own. It needs
the ISP's co-operation.

> 
> The problem is i do not want to use the best possible path ( cost vise ) to
> route a packet. I have to make use of all the availabe bandwitdh of the 3
> ISP's in the most efficient manner.

TC is the way to go !!


Ramin

> 
> I have read about TEQ traffic equalizer. But it has been mentioned that you
> cannot combine 3 different isps to act as one.
> As if you are using TEQ at one end, you are bound to have it at the other
> end.
> 
> with regards,
> Sushil Suresh

_______________________________________________
LARTC mailing list / LARTC@mailman.ds9a.nl
http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://ds9a.nl/2.4Routing/