ASR9K PPPoE / DHCPv6 profiles

[vikas.hazrati1]

Hello Everyone

In our current setup we are using ASR9K as BNG (PPPoE termination) and recently we starting offering dual-stack termination. For the DHCP_PD operation ASR9K has the role of the DHCPv6 server. For some subsribers we need to use DHCPv6 proxy so that the subscriber DHCPv6 requests are forwarded to a central server. Both setup must be active for PPPoE subscribers (we cannot move to DHCPv6 proxy config at once)

DHCPv6 server and proxy operations are defined in ASR9K using dhcp ipv6 profiles. I have not been able so far to find a way to select for some subscribers the DHCPv6 local server or the DHCPv6 proxy operation. (I was hoping to use a dhcpv6-class in subscriber requests to differentiate between each type of subscriber but have not been successful)

dhcp ipv6
 profile v6Proxy proxy
  source-interface TenGigE0/0/1/0
  helper-address vrf default 2001:100::1
 !
 profile v6Server server
  lease 1 0 0
  dns-server 2001:100::2
  prefix-pool DHCPv6_PD_POOL
 !
 interface subscriber-pppoe profile v6Server !!!! In this setup always v6Server profile is selected

!

The only command that seems to have any effect in selecting between different DHCPv6 profiles for PPPoE subscribers is the last one (interface subscriber-pppoe profile <Profile-Name>) but it can only make a static selection that will be applied to all sessions.

Is there any way to dynamically select in ASR9K for PPPoE subscribers different dhcpv6 profiles (override the selection made by interface subscriber-pppoe profile on a subscriber basis)?

[xthuijs · Accepted solution]

hi vikas,

yeah that is the current existing limitation we have whereby the Prefix-Delegation with a local server is tied to all subscriber access interfaces.

If you need more granularity we can provide that by using radius and an offbox dhcp server if that is an option for you.

This way you have the ability also to load a dhcp class from radius to signal to the dhcp server this class so a more selective pool can be used.

Mixing local dhcp server with offbox is currently not available.

I would like to do this functionality, but it is not a quick fix unfortunately. So if that on a per access interface bases local DHCP pool is a requirement, I would need to redirect you to your account team and facilitate a discussion with our eng group to see what can be done when.

Today; (using) radius (for pool selection on an OFF-box server) is your best option.

cheers!

xander

[vikas.hazrati1]

Thanks Xander

So far we use for all subscribers DHCPv6 local server operation in our BNGs. The only reason we wish to use for some the DHCPv6 proxy operation is that we will need for them extra DHCPv6 options (taking a static value common for all bindings of that pool - e.g. option 95) that are not supported currently in the pool definition of ASR9k. If this is easier to implement (ability to add in the pool definition an extra string defining an new DHCPv6 Option) we shall discuss this option with the local account team.

(The reason we try to avoid move to an external server for all subscribers is that we need to build this server infrastructure from scratch)

Thanx for your help!

[Arthur Guilherme Lima Ribeiro]

Ok.