Re: Routing issues

4 Dec 2011

      On Mon, Dec 05, 2011 at 07:38:30AM +1100, Martin Barry wrote:
...
...
The end result is to have a BGP router using two connections to announce
my /22 using my ASN, from the bird router I need to be able to send out
requests from my /22 over both interfaces (I have them weighted in the
bird config file so one gets more traffic).
...
which would balance the outgoing traffic. however the incoming comes over
based on bgp preferences(mainly as path) in the internet which results in a 
lot of asymetric routing. this will result in weird latency and problems with
one line affecting all connections.
Can the bgp routing path be set so incoming traffic prefers one connection over the other, as well?  I thought setting something like this:

protocol ospf {
        import all;
        export filter {
                ospf_metric1 = 1000;
                if source = RTS_STATIC then accept; else reject;
        };

        area 0 {
                interface "eth0" {
                        cost 50;
                        type broadcast;
                        hello 5; retransmit 2; wait 10; dead 20;
                };

                interface "eth1" {
                        cost 5;
                        type pointopoint;
                        hello 5; retransmit 2; wait 10; dead 20;
                };
                interface "*" {
                        cost 1000;
                        stub;
                };
        };
}

Would cause the path through the connection on eth0 to be 10x more prefered then the path through eth1, so incoming bandwidth should be split in about a 10-1 ratio.  So if I have eth0 as a 10 Gig connection, and eth1 as a 1 Gig connection, between using that for incoming traffic, and a multipath rule for outgoing traffic like this:

ip route add default scope global nexthop via 1.1.1.153 dev eth0 weight 10 nexthop via 2.2.2.81 dev eth1 weight 1

Would cause the two connections to be pretty uniformly used on incoming and outgoing traffic at a 10/1 ratio, allowing me to pretty fully saturate both lines?
...
My original answer relates only to traffic with a source address in your
Cogent /29 as this might be filtered by HE. You might need to do something
similar to traffic with a source address in your HE /29 as this might be
filtered by Cogent. Traffic with a source address in your /22 shouldn't have
that problem.
the policy routing should probably still be setup to allow testing of a
particular line because this way incoming and outgoing traffic do not have to
come over the same line.

mk

Re: Routing issues

dspazman＠epicup.com