[j-nsp] Multihoming servers to two Virtual Chassises

[Tim Durack]

Linux ethernet bonding/teaming does not need to be switch assisted. If you
configure one of the non-802.3ad modes (TLB etc) and put the two NICs on the
same broadcast domain, everything will work.

We use TLB mode, which gives 2x outbound, 1x inbound, due to the way arp
resolution works.

Tim:>

On Mon, Sep 15, 2008 at 5:16 AM, Tore Anderson <tore at linpro.no> wrote:

> Hi,
>
> I'm about to deploy a stack of EX 4200 switches in a new data centre.
> My original plan was to make a Virtual Chassis, split it in two stacks
> and put those stacks in separate corners of the room, and then let the
> servers (running almost exclusively Linux) multi-home to both stacks
> (using 802.3ad).  In addition to this the switches will function as
> distribution switches for more peripheral parts of the network.
>
> After playing around with the switches in a lab I'm not so sure if I
> want this after all.  If the switch functioning as routing engine
> fails, the switchover to the backup takes too long, and the OSPF
> sessions to the upstream MX 240-es are also lost.  This happens with
> GRES active and BFD off, too.  So a RE failover causes a 30-40 second
> L3 outage.  L2 forwarding seems unaffected, though.
>
> This isn't acceptable to me, so right now I'm looking at a setup where
> the stacks in each corner are separate VCes, which should ensure
> minimal L3 downtime if one fails - with BFD protection on both the up-
> and downstream OSPF sessions all traffic should be rerouted over the
> remaining VC within seconds.  Two active REs will also give me some
> additional resiliency in case of JUNOS bugs, so I quite like this
> solution.
>
> However now I have a problem with the multihomed servers.  Is it
> possible to have a 802.3ad LAG span multiple VCes (à la Nortel SMLT)?
> If not, does the EXes have any other nifty feature that could help me
> accomplish multihoming servers like that?  The doubling of bandwidth is
> not essential - high availability is what I need to accomplish, so
> simple failover is fine.
>
> I appreciate any suggestions you might have.
>
> BTW:  Anyone have an idea of when (if?) the EXes will support IPv6?
>
> Regards,
> --
> Tore Anderson
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