[c-nsp] Upgrading older 7600 with an ASR1000 router.. Questions..

Andriy Bilous andriy.bilous at gmail.com
Thu Dec 19 01:08:44 EST 2019

sorry, couldn't resist...

On Thu, Dec 19, 2019, 02:29 Howard Leadmon <howard at leadmon.net> wrote:

>   I know a while back I had asked about replacing an old 7606/RSP720 I
> had handling routing, and I got some great info from the group that was
> much appreciated.    I ended picking up an ASR1000 series router to use
> in place of the 7606, or so I thought, I am wondering now if I actually
> still need both.
>   The 7606 handled both Layer 2 and Layer 3 functions fairly well for
> us, for a great many years, and I guess I just got very used to this
> fact.  The one thing that always worked really well was that we had a
> bunch of Ethernet multi-point links from providers like Zayo and Comcast
> that interconnected a bunch of our different locations, as they were L2,
> I simply setup a tag that ran to a location and off it went.   Most of
> the remote locations are all 4500 series switches, so using L2 trunks
> made this just work.   So on the 7606, I had trunks to the various
> providers, as well as local trunks to some of the other switches in the
> racks,  my transit links, and a few clients.
>   So enter the ASR1000 and I thought great, this is a simple change as I
> should just be able to copy most of my 7600 configs across into the ASR
> and life will be good.   The I went to setup a trunked port to bring the
> existing equipment into the new ASR.   Surprise, unlike the old 7600
> there is no turning a port in the ASR into a switchport, or not that I
> can find, so it looks very much like it's an L3 device for the most
> part.   Well that sure blows up all the vlan interfaces/trunks that were
> in the 7600 that will not transfer into the ASR.
>   I am wondering if I need to keep the old 7606 in service to handle the
> L2 trunking terminations and pasthroughs, and just setup sub-interfaces
> on the ASR to handle any of the needed L3's connections that need to do
> routing via the ASR, like all of our transit and peering links?
>   I actually have a couple L2 trunks, where some of the VLAN's are L3
> connections that I picked up on a VlanXX interface locally, but at the
> same time I also  have other L2 Vlan's that needed to come in one port,
> and then head back out another port to a different device.  I have
> googled around a bit, but heck if I see anyway to do this mixed
> environment on the ASR, where on my old 7600 it just worked, and has
> worked well for a great many years.   Heck the main reason I am ditching
> the old 7606 workhorse is that as we all know carrying full routing
> tables to multiple providers, well it's getting very long in the tooth
> without cutting out some routes.
>   I am sure some here have had to deal with something like this at some
> point, so I hope someone can toss me some suggestions or insight on the
> best way to handle this, or do I just delegate the new ASR as just a BGP
> router, and still pass it all back through the old 7600 for now.
> Thanks as always for any input on how to approach this task..
> ---
> Howard Leadmon
> PBW Communications, LLC
> http://www.pbwcomm.com
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