RE: Question regarding Split Access description

Linux Advanced Routing and Traffic Control

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All,

 

Further to this email below, in order to get split access load balancing across the two SHDSL services in the diagram below, I’m thinking it makes more sense to have the standard split access configuration (as outlined in section 4.2 of the LARTC document) would make more sense. That is, on the ETH RTR, have this:

 

          ip route add $P1_NET dev $IF1 src $IP1 table T1
          ip route add default via $P1 table T1
          ip route add $P2_NET dev $IF2 src $IP2 table T2
          ip route add default via $P2 table T2
          ip route add $P1_NET dev $IF1 src $IP1
          ip route add $P2_NET dev $IF2 src $IP2
          ip route add default via $P1
          ip rule add from $IP1 table T1
          ip rule add from $IP2 table T2
 

 

 

                                                                          ________
                                          +------------+                 /
                               y.y.y.1/30 |            |                |
                            +-------------+ SHDSL RTR1 +-- SHDSL line--
        __      y.y.y.2/30  |             |            | b.b.b.b/32    /
    ___/  \_         +------+-------+     +------------+              |
  _/        \__      |     if1      |                                 /
 /             \     |              |                                |
| Local network -----+if3 ETH RTR   |                                |     Internet
 \_           __/    |              |                                |
   \__     __/       |     if2      |                                 \
      \___/          +------+-------+     +------------+               |
                x.x.x.2/30  |             |            |                \
                            +-------------+ SHDSL RTR2 +--SHDSL line--
                               x.x.x.1/30 |            | a.a.a.a/32     |
                                          +------------+                  \________

 

 

This way the complexity in having multiple default routes from two IP ranges (one from each provider) from the hosts in the local network (web app server, email, etc) is removed by having just the IF3 interface on the ETH RTR as the default route for the local network servers, and then using the split access approach above on the ETH RTR to do the outbound load balancing.

 

Can anyone confirm if this is a sensible and doable approach?

 

Regards

 

Adam

 


From: Adam Neat [mailto:adamneat@xxxxxxxxx]
Sent: Sunday, 24 December 2006 11:03 AM
To: 'lartc@xxxxxxxxxxxxxxx'
Cc: 'bert.hubert@xxxxxxxxxxxxx'
Subject: Question regarding Split Access description

 

Hi All,

 

I’m a big user of the LARTC document but am currently stuck with a question around section 4.2 (http://lartc.org/howto/lartc.rpdb.multiple-links.html) in relation to “Routing for multiple uplinks/providers”. 

 

I’m wanting to do a similar setup to the diagram where I have – lets just say for the moment – two uplink providers where I want to route over two SHDSL lines for performance and availability. I have two separate IP ranges; one from each, and I plan to give key servers on the Local Network two IPs.

 

In your example your ip route commands are inferring one router – if I had two routers, one connected to each of the two providers, are those setup commands applicable, by changing the destination values to be the internet Ethernet interface of the other router for the other link? Eg:

 

Router 1 – Provider 1:
 
          ip route add $P1_NET dev $IF1 src $IP1 table T1
          ip route add default via $P1 table T1
          ip route add $P2_NET gw $RTR2 src $IP2 table T2
          ip route add default via $P1
 
          ip rule add from $IP1 table T1
          ip rule add from $IP2 table T2
 
          ip route add default scope global nexthop via $P1 dev $IF1 weight 1 \
            nexthop via $P2 gw $RTR2 weight 1
 
 
 
Router 2 – Provider 2:
          ip route add $P2_NET dev $IF2 src $IP2 table T2
          ip route add default via $P2 table T2
          ip route add $P1_NET gw $RTR1 src $IP1 table T2
          ip route add default via $P2
 
          ip rule add from $IP1 table T1
          ip rule add from $IP2 table T2
 
          ip route add default scope global nexthop via $P2 dev $IF1 weight 1 \
            nexthop via $P1 gw $RTR1 weight 1
 
 
 
Then for each machine on the network, would I give them two default routes (one to each gw) or?
 
I can’t seem to get my head around how this should work and I’m low on spare lab machines to test this out.
 
Appreciate any guidance,
 
Season Greetings and Regards
 
Adam
 
 
 

 

 

 

 

 

 

 

 

 

 

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