[j-nsp] Multihome SRX650 2 default routes

[Tim Eberhard]

ECMP doesn't work as of today in branch series SRX's if "advanced"
security features are enabled such as NAT, IDP, ALG's, and such. The
problem is with the flow module and where routing decisions take
place.

It will work if the both destination interfaces are in the same zone
and you're using basic security policies. If you require any form of
NAT (which is typical with two ISP links) then this will not load
balance across the two paths.

I've tested this in my lab and it's a known limitation within Juniper.
The forwarding table shows both routes (creating two static default
routes will do the trick) then enabling layer 3 load balancing but the
routing table will always prefer one route and send traffic down only
that route.

There are hacks (and not very clean ones to be honest) involving
multiple routers one to terminate the inbound traffic and nat it, then
the second to do the ECMP. This is not ideal and I wouldn't ever
recommend it for a customer environment.

Best of luck. I hope the branch guys can get this fixed. ScreenOS has
been able to do this for a while. I'm told this may get addressed in
12.1 but nothing is official.
-Tim Eberhard



On Fri, Aug 26, 2011 at 10:33 AM, Daniel M Daloia Jr
<daniel.daloia at yahoo.com> wrote:
> Thanks Ben. This would be the case with two separate virtual routers since they would have to be in different security zones which why I didn't think that would work. I would like to keep the firewall in flow mode.
>
>
> I found some information on multipath which I am going to lab up soon. I can keep the interfaces in the same security zone if that is the case and create a peer group for the two neighbours.
>
>
> http://www.juniper.net/techpubs/en_US/junos10.4/topics/reference/configuration-statement/multipath-edit-protocols-bgp.html
>
> Thanks!
>
>
>
>
> ________________________________
> From: Ben Boyd <ben at sinatranetwork.com>
> To: Daniel M Daloia Jr <daniel.daloia at yahoo.com>
> Cc: "juniper-nsp at puck.nether.net" <juniper-nsp at puck.nether.net>
> Sent: Friday, August 26, 2011 10:44 AM
> Subject: Re: [j-nsp] Multihome SRX650 2 default routes
>
>
> If you install both routes in the forwarding table you'll probably end up dropping a lot of your traffic.
>
> The SRX is a stateful firewall, so if you sent traffic to one provider and got it back on another it would drop the traffic.
>
> It would be best to do this in a router or to load balance per prefix with as path prepending going out and local pref coming in.
>
> Anyway, here's how you would do it, but be careful.
> root# show
> policy-statement TestLBOut {
>     then {
>         load-balance per-packet;
>     }
> }
>
> lroot# show routing-options
> forwarding-table {
>     export TestLBOut;
> }
>
>
>
> Thanks,
> Ben Boyd
> ----------------------
> Sent from my iPhone
>
> On Aug 25, 2011, at 11:09, Daniel M Daloia Jr <daniel.daloia at yahoo.com> wrote:
>
>
> Hi Folks,
>>
>>Is it possible to install 2 BGP default routes from 2 ISPs to provide load balancing with an SRX650 cluster? Both ISPs are same speed. I was thinking this may be possible with importing the routes into inet.0 from separate virtual routers which have the interfaces facing the 2 ISPs in them, but the ISP interfaces would have to be in separate security zones which wouldn't agree with the security policy and NAT. Anyone have any ideas or can point me to some documentation that will help? I suppose I can buy a separate set of routers to run BGP and use an IGP to load balance, but doing it with the single cluster would be nice.
>>
>>Thanks!
>>_______________________________________________
>>juniper-nsp mailing list juniper-nsp at puck.nether.net
>>https://puck.nether.net/mailman/listinfo/juniper-nsp
>>
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