Re: Junos Asymmetric Routing

[Jian Gu <guxiaojian () gmail com>]

Then you should look at your IGP, right?

On Fri, May 28, 2010 at 8:09 AM, Ken Gilmour <ken.gilmour () gmail com> wrote:
> Hi Jian,
>
> Yes sir that's what I thought too. The packets are being NATted (and I also
> used a bit of DNAT for port forwarding to test the theory) but the result is
> the same.
>
> Regards,
>
> Ken
>
> On 27 May 2010 23:46, Jian Gu <guxiaojian () gmail com> wrote:
> > Wouldn't simply configure source NAT on firewall 2.2.2.1 resolve the
> > problem gracefully? when connection requests coming in through ISP2,
> > source NAT the incoming traffic's source IP with IPs on firewall
> > inside interface, that way when server replies, firewall 2.2.2.1 will
> > guarantee to receive the ACK because ACK traffic won't follow default
> > routing to ISP1.
> >
> > On Thu, May 27, 2010 at 4:27 PM, Ken Gilmour <ken.gilmour () gmail com>
> > wrote:
> > > Hi all,
> > >
> > > I have a very peculiar situation here that i seem to have difficulty
> > > explaining in such a way for people to understand. I just got off the
> > > phone
> > > to the Juniper Devs after about 4 hours with no result. They understand
> > > the
> > > problem but can't seem to think of a working solution (last solution led
> > > to
> > > the primary firewall hard crashing and then failing over after a commit
> > > (which also makes me wonder what made the primary crash and not the
> > > secondary)). I am wondering if there is anyone "creative" on the list
> > > who
> > > has encountered and worked around this problem before...
> > >
> > > Here goes *sigh*
> > >
> > > ISP1 - 1.1.1.0/24
> > > ISP2 - 2.2.2.0/24
> > >
> > > ISP1 is the default gateway, ISP2 is a backup provider but which is
> > > always
> > > active. Client comes in on ISP1's link, traffic goes back out on ISP1s
> > > link.
> > > Client comes in on ISP2's link (non default gateway) but for some
> > > reason,
> > > the packets seem to be going back out through the link for ISP1.
> > >
> > > So look at it this way:
> > >
> > > SYN comes from client at 3.3.3.3 aimed at 2.2.2.2, packet is received by
> > > the
> > > firewall. Firewall sends a SYN/ACK but the firewall at 1.1.1.1 sees it
> > > in
> > > TCPDump, the firewall at 2.2.2.1 never sees it.
> > >
> > > Here's a log snippet (I can send you more if you need:
> > >
> > > May 27 21:38:49 21:38:48.1509569:CID-1:RT:  route lookup: dest-ip
> > > 3.3.3.3 *orig
> > > ifp reth3.0* *output_ifp reth2.0* orig-zone 19 out-zone 19 vsd 3
> > >
> > > You will see that the orig and out zones are the same zone, however this
> > > was
> > > a last ditch effort (putting both interfaces into one zone, effectively
> > > creating a swamp).
> > >
> > > Our current (non-preferred) solution is to put match-all rules on our
> > > Catalyst 6513s and put both providers into a swamp and the switch will
> > > then
> > > intercept the packets if they are destined for the wrong interface and
> > > send
> > > them out the right one based on a bunch of boolean.
> > >
> > > We've tried setting up a virtual instance on the offending interface and
> > > a
> > > firewall filter, but this had little to no effect (at one point it
> > > stopped
> > > passing the packets to the end machine altogether). We're using small
> > > SRX
> > > 650ies. Why do we want to do it this way you ask? In the event of a BGP
> > > session failure we need to be able to use our statically routed IPs and
> > > rely
> > > on someone else.
> > >
> > > Thanks!
> > >
> > > Ken