Comments in-line...
On 4/24/2012 1:48 PM, Clarke Morledge wrote:
Stefan,
I was just hunting through your blog for ideas when I saw your post :-)
Thanks for jumping in. A few responses in-line below.....
On Tue, 24 Apr 2012, Stefan Fouant wrote:
If that adjacency goes down, a simple floating static (static route w/
higher preference than the dynamic BGP/IS-IS route) can be used
pointing to next-table will do the trick. No need to used
Logical-Tunnels or use auto-export.
If my two routers were directly connected all of the time, this would be
fine. But I'm also thinking of the case of when there might be another
L3 hop between the two routers. I guess I could insert another floating
static on the third router, but that just seemed to add a little more
complexity to me. I was hoping for a way to just let the dynamic routing
protocols do the work for me instead of fooling with a bunch of statics
with filter-based forwarding. Don't get me wrong, I like FBF. I was just
hoping to leverage dynamic routing more.
I guess what I was referring to is that you don't really need to have
the MX West device be used at all in the event that the L2 Packet
scrubber dies, as per the restrictions in your initial email:
"I also need to have a redundant path, preferably passing through the
other core router (MX West). In the event that the Layer2 box dies, or
if the MX East core router dies, unfortunately traffic will not get
inspected but I will still have connectivity between the North and South
VRFs via the MX West core router. "
What I'm saying is that if the Packet Scrubber dies, the protocol
adjacency through the VR North and the VR South on the MX East device
will fail, and you could simply route directly from VR North to VR South
on the same device by using simple floating static route pointing to
next-table. In other words, if traffic arrives in VR North on MX East
and packet scrubber device dies, then the floating static in
vr_north.inet.0 will point to vr_south.inet.0, and vice-versa for
traffic in the reverse direction. So you have no need for a redundant
path through MX West and that would only be used in the event that the
entire MX East device goes down.
Of course, in your case you've got not just two VRFs but also an East
and West path which further complicates things - why not just connect
the MX West device into your L2 Packet Scrubber as well and keep
things the same on both the East and West device so that you can take
full advantage of two planes. This will keep configurations uniform
regardless of whether traffic comes in on the East or West devices.
I should have given the reason why I do not put the L2 scrubber between
the two routers: conservation of fiber. I already have fiber connecting
the routers in different wiring centers for traffic that does not need
to be scrubbed. Chewing up another set of strands is much more expensive
than simply connecting both sides of the L2 scrubber to just one router
in the same rack.
Makes sense...
--
Stefan Fouant
JNCIE-SEC, JNCIE-SP, JNCIE-ENT, JNCI
Technical Trainer, Juniper Networks
Follow us on Twitter @JuniperEducate
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