[cisco-bba] 7204VXR vs ASR1001-x (as LNS / provider is LAC)

[James Bensley]

On 28 March 2017 at 19:55, Bruce Technical <brucetechnical at gmail.com> wrote:
> P.S. why would you not recommend ASR vs ASR-X? (There is a huge price
> difference on eBay).
>
> On Mar 28, 2017 12:07 PM, "Bruce Technical" <brucetechnical at gmail.com>
> wrote:
>>
>> ***sending again with reply all and a minor change***
>> Hi James,
>>
>> Not late at all. We are deciding this week to go with one ASR-x or
>> multiple 7206vxr.
>>
>> 1- How would couple 7206vxr work together when our ISP is wanting to
>> connect to LNS first and not Radius?
>>
>> 2- I am asked to pick single or multimode fiber. For 7206vxr which one
>> should I pick and which is supported?
>>
>> 1000 customers is not bad for the price of a VXR.
>>
>> Best Regards,



Hi Bruce,

>> 1- How would couple 7206vxr work together when our ISP is wanting to
>> connect to LNS first and not Radius?

That's a bit odd. I would expect the normal procedure to be as follows
(visual representation here:
https://null.53bits.co.uk/index.php?page=adsl2-2-ppp-over-l2tp-life-cycle),
sorry if you know all this it’s not meant to be patronising:

- CPE comes online and wholesaler LAC queries the CPE for authentication details
- Wholesaler LAC sends access-request using the CPE provided
authentication details to wholesaler RADIUS to check if these details
are correct
- Wholesaler RADIUS see's these detail belong to another ISP (you!) an
will proxy the authentication request to your RADIUS (forwards your
RADIUS the access-request
- Your RADIUS authenticates the user and in the access-accept response
to the wholesalers RADIUS send your tunnel-endpoint IP and password
(your LNS IP and password)
- When wholesaler RADIUS response sends this access-accept back to the
LAC in response to the LACs access-request
- The LAC builds the L2TP tunnel to your LNS
....

>From then on it’s all within your domain of responsibility.

We have one wholesaler who's LACs speak to our RADIUS servers, so they
are dual purpose devices, LAC and RADIUS Proxies. If the wholesaler
wants their LAC/BRAS to talk to your LNS directly without any RADIUS
involvement, how will you be able to dynamically return your LNS IP,
unless they have fixed details: *@realm1.net > 1.2.3.4 (your LNS IP),
*@realm2.net > 5.6.7.8 (another of your LNS IPs) etc.

With multiple LNS as we heave, either the wholesaler RADIUS asks our
RADIUS for the tunnel-endpoint IP and we return multiple IPs with the
same preference and they round-robin across them (we can offset the
preference in the RADIUS reply if we want to traffic steer certain
sessions to certain LNS devices), or in the case of that “other”
wholesaler, their LACs talk to our RADIUS then build the L2TP to our
LNSs and again round-robin of the multiple IPs returned.


>> 2- I am asked to pick single or multimode fiber. For 7206vxr which one
>> should I pick and which is supported?

Both are supported (you would purchase an MM or SM SFP/GBIC to go into
the chassis line card, the transceiver “handles” the MM/SM port and
the chassis is agnostic of it more or less). Multimode is usually
cheaper although single mode will carry for a greater distance. You
just need to weigh up what’s right for you there, nothing to
complicated.


>> 1000 customers is not bad for the price of a VXR.

I’m in the UK, with the rise of FTTC that number will probably come
down. CPU == throughput (more or less) on the 7200 series, slowly we
are moving from 1000x 8Mbps ADLS to some hundreds of 40-80Mbps FTTC.
7200s are so cheap you can scale our horizontally easily, just deploy
more LNS’s and return the additional IPs in your RADIUS response.
However 10x 7200s is a lot more hassle than say 2x ASR1006-X. 7200s
are so cheap though, have one if not two in the lab, probably some
others lying around in storage we’ve forgotten about etc. It’s
expensive to have an ASR 1000 series sitting in the lab for very
occasional usage.


> P.S. why would you not recommend ASR vs ASR-X? (There is a huge price
> difference on eBay).

The non-X versions either are EoS already or will be soon. The X
versions are pretty much the defacto for the 1000 series devices. The
H-X versions are out and they will eventually replace the X versions
but that is still some years away. So for now if someone was going to
put in a new deployment I’d recommend the X versions as the death
knell has been rung for the non-X versions (bug fixes, TAC support,
code upgrades etc). The X versions are more expensive as they are the
next generation from the original non-X versions and much faster and
more scalable.


Cheers,
James,