[c-nsp] DHCPv6 on IOS-XR with multiple pools?

[Nathan Ward]

Hi,

> On 14/11/2018, at 9:29 AM, Bryan Holloway <bryan at shout.net> wrote:
> 
> Howdy all ...
> 
> Consider a Cisco 4900 with two L3-anchored VLANs in a GPON/FTTx-type scenario: one for business customers, and one for residential.
> 
> Both VLANs have a unique local /64 for customer ONTs, but I also want to do PD with /56s.
> 
> I learned quickly that the 4900 doesn't do DHCPv6 serving, but it will happily relay.
> 
> Upstream we have an ASR running 5.3.4.
> 
> On it I've been successful in creating "dhcp ipv6" server profiles, "prefix-pools", "address-pools" and subsequently anchoring them to the downstream interface facing the 4900, but I don't appear to be able to differentiate between pools for the two VLANs.
> 
> That is, I see assignments, but I'm not sure if the IOS-XR implementation supports having multiple prefix-pools and address-pools bound to a single downstream interface. It always appears to pick one or the other, no matter what I do with the config.
> 
> I see that there is a way to create "class"es within the "dhcp ipv6" config, but it doesn't seem to really do anything. That is, I can create a RESIDENTIAL class with its own address-pool and prefix-pool, and likewise a BUSINESS class with its own address-pool and prefix-pool, but the ASR doesn't seem to match the incoming request from the relaying 4900 interface and choose the correct pool(s).
> 
> Anyone made this work before? I can send config examples if it helps. I've searched the docs but what I've found is a little sketchy.
> 
> N.B.: And yes -- I should probably be doing this with a proper DHCP server ... but I'm in a bit of crunch.

Generally you want a RADIUS server. If you’ve got one, you can set a “subscriber:dhcpv6-class” Cisco-AVPair to tell it which DHCP class you want to use. You also have subscriber:dhcp-class if you want to use that.

You say you have a single interface, but you also say “from the relaying 4900 interface” - does your BNG see your residential and business customers on different interfaces, or is it all on one interface? Ah, I also see you say “2 VLANs” ? Can you run a different DHCP profile per VLAN (i.e. per interface..?), or does that not solve it?

Can the 4900 set a DHCP option? I believe you can match to a class based on DHCP options on the ASR9k, but I’ve not personally done this. It may only be when doing DHCP proxying on the ASR9k, not sure if this applies to using the ASR9k as a DHCP relay/proxy target.

--
Nathan Ward