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

[James Bensley]

On 11 February 2017 at 20:03, Bruce Technical <brucetechnical at gmail.com> wrote:
> Hi,
>
> We are entering the DSL reseller market and costs for ASR1001-x or ASR1002-x
> are in the $20k+ for Cisco ASR1001-x + IP Advance Licenses + 500 Sessions.
>
> We are considering used 7204VXR. What is it in ASR1001-x that 7204VXR can't
> do for example?
>
> Our Service Provider require LNS/LAC, L2TP, VRF, and Radius.
>
>
> Thanks,
> Bruce


Hi Bruce,

I know this is a late response (I've been away and I'm catching upon
emails), but for the sake of the list archives it might help someone
else.

As others have already mentioned the ASR1000 series will scale much
further and so it costs more. For the price of an ASR1001-X (I
wouldn't bother with non-X versions anymore) you can buy several
7206VXRs with NPE-G2 but you won't have TAC support and scaling limits
(only 1G interfaces and stuff like NAT quickly chews up CPU).

> Our Service Provider require LNS/LAC, L2TP, VRF, and Radius.

This is what I would call the basic feature set of an LNS so both ASR
and 7200 series devices provide both functions as well as stuff like
QoS and NAT.

We don't scale our 7200s above 1k sub's. We are an LLU provider but
when it comes to FTTC/VDSL we normally terminate that locally in the
PoP. So if we take a wholesale ADSL and VDSL connection into a central
LNS from a 3rd party supplier we have to be weary that the 7200's on
have 1G interfaces as we can sell bonded ADSL & VDSL over the 3rd
party L2TP tunnels so 1G == 1k sub's is about right in my head.

Someone mention about the RADIUS challenges for ASR's, I have some
notes on example RADIUS configs here:
https://null.53bits.co.uk/index.php?page=avpairs

If you look under: Cisco new style ("ip") VSAs

ASRs need to use these style of VSAs on the virtual access interface.
Further down are the "older" style VSAs however both types are support
on the 7200s with a 15 IOS so initially it did catch us out when
migrating to ASRs but we just did a mass backed update in
Postgres/RADIUS so all accounts use the "newer" style and there all
users could be connected to either a 7200 series or ASR series LNS.

If you're going to deploy an ASR maybe check out these notes I made on
initial limitations and issues we hit:
https://null.53bits.co.uk/index.php?page=asr-ios-xr-lns-config

some of them are resolved now in newer XE versions and I haven't had
time to update the notes but it’s worth double checking in the Cisco
doc's for yourself. For example, we just dropped L2 port-channels in
exchange for multiple 1G layer 3 interfaces and/or 10G interfaces,
they caused too much trouble with QoS and NetFlow and SNMP monitoring.

You had some queries regarding load balancing across multiple LNS
devices. Assuming you use RADIUS on your side to speak with your 3rd
party provider (I highly recommend this) you can return the IP of all
3 LNS devices (or however many you have) back to the provider for any
user or realm and they should round-robin the session across those LNS
device IPs. You can also adjust the priorities in your RADIUS response
if you want to have un-equal load balancing. Any good 3rd party
provider should support this.

Cheers,
James.