ASR9000 Understanding the BNG configuration (a walkthrough)

[xthuijs]

Introduction

In this document we're walking through a configuration setting up BNG for IPoE and PPPoE. The Setup for this configuration is similar to the setup you can see in the YouTube video for an ip sessions demo.

Problem Description

Detailed description of how to set up the configuration and the options establishing PPPoE and IPoE sessions. Understanding the anatomy of a control policy language.

Setup

Configuration and Explanations

hostname A9K-BNG

radius-server host 3.0.0.38 auth-port 1645 acct-port 1646

!Radius-server definition with ip address and UDP ports it is going to !use.

key 7 045802150C2E

!Secret key for the radius communication

timeout 1

!Maximum time waiting for response

retransmit 1

!Maximum number of times you retransmit the request, after waiting <timeout> time.

!COA server definition

aaa server radius dynamic-author

port 1700

!COA port is standard 1700

client 3.0.0.1 vrf default server-key 7 13061E010803

client 10.86.1.49 vrf default server-key 7 14141B180F0B

!The clients from which we are going to accept a COA Response.

!Attribute definitions that we can reference for the nas-port

!building.

!”MY_AUTH” will take the mac address, circuit ID and remoteIDand

!append them together separated by hash signs. If one of the fields is

!not available, an empty string will be provided for that portion.

!example 0000.1111.2222##remoteid or 0000.2222.1111#circ#remote

!

aaa attribute format MY_AUTH

mac-address plus circuit-id plus remote-id separator #

!

aaa attribute format NAS_PORT_FORMAT

circuit-id plus remote-id separator .

! Nas-port computation for PPPoE(32) and if not pppoe then follow the

! global (non typed) logic

aaa radius attribute nas-port format e SSAAPPPPQQQQQQQQQQVVVVVVVVVVUUUU type 32

aaa radius attribute nas-port format e SSAAPPPPQQQQQQQQQQVVVVVVVVVVUUUU

!Set up the XR nas-port-id (attr87) for sessions following the nas-

!port format instructions above.

aaa radius attribute nas-port-id format NAS_PORT_FORMAT

!Set up for AAA usage. Note that we don’t have “aaanew-model” in

!XR. Also “subscriber” is used for BNG. Method “PPP” is used for

!serial PPP.

aaa authorization subscriber default group radius

aaa authentication subscriber default group radius

!DHCP configuration

dhcp ipv4

!specify a profile name and define what method is used, relay, proxy

!or snooping.

profile AutoSelectGiaddr proxy

!Different classes may be defined. This is not necessarily the

!vendor class, but here we can check certain options in the discover

!to selectively set the helper address and giaddr. That last one

!will affect the pool we’re going to use on the dhcp server.

class HardPhone1

match option 60 hex 4861726450686F6E6531 mask 0

!the option 60 is vendor-class followed by a hex string. I chose it

!to match the “class” section from the line above, but that is not

!necessary. The mask defines which bytes are must match and don’t

!cares. Mask of 0 means full match.

helper-address vrf default 81.1.1.2 giaddr10.1.1.254

!

class HardPhone2

match option 60 hex 4861726450686F6E6532 mask 0

helper-address vrf default 81.1.1.2 giaddr172.28.15.254

!

relay information option

relay information policy replace

relay information option remote-id testme

relay information option allow-untrusted

! This configuration above defines the option 82 handling.

! Allow untrustedmeans that we accept dhcp discovers with a 0.0.0.0

! giaddr, which is normally the case when there is no relay between

! the client and the 9k.

Relay information Policy:

Case #

Received Packet Option-82 Suboptions

Configured Option-82 Suboptions

Forwarded Packet Option-82 Suboptions for Full-Option-82 keep

Forwarded Packet Option-82 Suboptions for Individual-Suboption keep

Forwarded Packet Option-82 Suboptions for replace

1

“rx-cid”

“rx-rid”

“in-rid”

vpn-id

“rx-cid”

“rx-rid”

“rx-cid”

“rx-rid”

vpn-id

“rx-cid”

“in-rid”

vpn-id

2

“rx-cid”

“in-rid”

vpn-id

“rx-cid”

“rx-cid”

“in-rid”

vpn-id

“rx-cid”

“in-rid”

vpn-id

3

“in-rid”

vpn-id

“in-rid”

vpn-id

“in-rid”

vpn-id

“in-rid”

vpn-id

! Define the interfaces and the attached profiles

interface Bundle-Ether100.2 proxy profile AutoSelectGiaddr

interface Bundle-Ether1001.2 proxy profile AutoSelectGiaddr

!

pppoe bba-group X

tag ppp-max-payload minimum 1200 maximum 2000

service selection disable

! PPPoE group definition. Currently there is limited service selection

!support (just matching on service name). The COS values for PPPoE

!control can be defined here and the processing/support for max-

!payload tag. In IOS you could configure the processing of vendor-tags

!and strip them selectively. In XR we always process the tags and we

!always strip them from a PADR

!IP address pool definition

pool vrf default ipv4 POOL

address-range 199.1.1.1 199.1.255.255

!

!The dynamic templates are like IOS virtual-templates. The base !configuration for each session is defined here. L3 features as well !as PPP specific parameters are defined here.

dynamic-template

type ppp TPL

ppp authentication chap

ppp ipcp dns 1.2.3.4 1.2.3.3

ppp ipcp peer-address pool POOL

ipv4 unnumbered Loopback1000

!

type ipsubscriberIPSUB

ipv4 unnumbered Loopback12

ipv4 access-group IPSUB_FAIL_ACL ingress

ipv4 access-group IPSUB_FAIL_ACL egress

!Few ACL definitions referenced in the radius profile, qos class-maps

!or in the dynamic template.

ipv4 access-list PERM_ALL

10 permit ipv4 any any

20 permit icmp any any

!

ipv4 access-list lab-video

20 permit udp any any eq 5544

30 permit udp host 49.1.1.2 any

!

ipv4 access-list IPSUB_FAIL_ACL

5 permit icmp any any

10 permit tcp any host 49.1.1.2 eqwww

15 permit tcp host 49.1.1.2 eqwww any

20 deny ipv4 any any

!QOS class-map used in COA parameterized QOS requests

!remember that with pQOS you can define the policy-map via RADIUS,

!however you need to define your class-maps locally in XR.

class-map match-any VIDEO

match access-group ipv4 lab-video

end-class-map

!

class-map match-any 3play-voip

match access-group ipv4 telnet

end-class-map

!These are the class-maps used later in the control policy. You can

!match on various aspects of the interface/session. Like username,

!domain. In this case we have simple class-maps that match on the

!protocol so we are doing to differentiate between PPP and IPsubs

!

class-map type control subscriber match-any PPP

match protocol ppp

end-class-map

!

class-map type control subscriber match-any DHCP

match protocol dhcpv4

end-class-map

!

!In this sample class-map we are taking the username and apply a

!separator switch on it as defined in the “format DOMAIN” attribute

!definition and see if that domain name matches “vrf_vpn”

class-map type control subscriber match-any matchdomain

match domain vrf_vpn format DOMAIN

end-class-map

!

!This is the most important part, the XR control Policy.

policy-map type control subscriber sub

event session-start match-first

!

!Events: during the session life time, various events are triggered. !In this case a session-start event we provide a handler for. This is

!the reception of a PADI for pppoe sessions or a dhcp discover for IP

!sessions.

!The match-first describes that we are only handling one class of the !event, and the class that we match first.

!This as opposed to match-all, which means that we will traverse all

!classes to see if they match and execute the actions defined

!underneath the class.

!

Event	What does it do or when is it triggered?
session-start	when we get the first sign of life (for pppoe that is at PADR)
session-activate	This is done at the authentication phase – i.e. when we’ve got the username/password (or challenge/response) (PPPoE ONLY)
authentication-failure*	when we receive an access-reject from radius
authentication-no-response	when the method list for authentication request does not return any response (success/reject)
authorize-failure*	when we receive an access-reject from radius
authorize-no-response	when the method list for authen or author does not return any response (success/reject)
service-stop	when a service that is applied to the session is removed or stopped

class type control subscriber CLASS do-until-failure

!

!CLASS: Underneath that event, we define the classes. In this example

!I created 2 classes to match specifically on DHCP and PPP sessions.

!I can have 1 control policy with 1 event, and then the class

!differentiator to determine what I want to do specifically/separately

!for both session types.

!

Do until?	What does it do?
do-until-failure	Until we receive a failure (eg access reject or no radius response or feature application failure) We stop the execution.
do-until-success	When we successfully executed the task we stop.
do-all	Regardless of the success or failure all actions are executed

!

10 activate dynamic-template TPL

!

!Activation of the dynamic template configuration. PPP will take the !LCP parameters and auth protocol from there.

!

!Class-actions:

!

event session-activate match-first

class type control subscriber CLASS do-until-failure

10 activate dynamic-template TPL

20 authenticate aaa list default

• Authenticate: Use the username and password from the line and send it to the servers defined in the list

• Authorize: More flexible then authenticate, still the SAME radius request (access-request) but flexibly formatted with a username composed of different information such as domain, circuit-id, nas-port etc

Note: Because authenticate uses the line username, it is generally useless on the session-start event, the authorize with which you compose the username based on mac/circuit id etc is very useful in both session start and activate

!

!

end-policy-map

!

policy-map type control subscriber ipsub

event session-start match-first

class type control subscriber DHCP do-until-failure

10 authorize aaa list default identifier source-address-mac password cisco

! Use the authorize here to compose the username to be sent to

! radius. In this case we use pw cisco as the password.

!

end-policy-map

! Define the bundle-ether master and configure for destination ip

! based loadbalancing, this so each subscriber hashes all its traffic ! onto one member only for accurate QOS

interface Bundle-Ether100

bundle load-balancing hash dst-ip

! The IP session interface must have an ip address. This in order to

! accept ip packets, the dhcpdiscover.

! If the unicast flag is set, like in MAC OSX or WXP (IOS dhcp client

! leaves the broadcast flag), then this address MUST be the same as

! the subnet for the ip sessions. If it is not the same we can’t

! unicast the offer.

interface Bundle-Ether100.2

ipv4 address 87.78.77.1 255.255.255.0

service-policy type control subscriber ipsub_fancy_auth

encapsulation dot1q 2

ipsubscriber ipv4 l2-connected

initiator dhcp

initiator unclassified-source

!

! Define the bundle sub interface for the right vlan, enable for PPPoE

! via the bba-group and attach the control policy

interface Bundle-Ether100.20

service-policy type control subscriber sub

pppoe enable bba-group X

encapsulation dot1q 20

! Loopback interface for ppp sessions

interface Loopback1000

ipv4 address 101.101.1.1 255.255.255.255

!

interface GigabitEthernet0/0/0/19

! Enable LACP on the bundle member and set it to bundle-e100

bundle id 100 mode active

load-interval 30

!

interface GigabitEthernet0/1/0/19

! Enable LACP on the bundle member and set it to bundle-e100

bundle id 100 mode active

load-interval 30

Show command verification

RP/0/RSP0/CPU0:A9K-BNG#show subscr ses all det
Mon Nov 7 17:20:27.701 EDT
Interface: Bundle-Ether100.2.ip5
Circuit ID:
Remote ID: testme
Type: IP: DHCP-trigger
IP Address: 172.28.15.1, VRF: default
Mac Address: 0019.2f43.9a38
Account-Session Id: 00000044
Nas-Port: 67108896
Username: unknown
Subscriber Label: 0x00000044
Created: Thu Nov 3 16:26:33 2011
State: Activated
Authentication: unauthenticated
Access-interface: Bundle-Ether100.2
Policy Executed:
policy-map type control subscriber ipsub_fancy_auth
event Session-Start match-first [at Thu Nov 3 16:26:33 2011]
class type control subscriber DHCP do-until-failure [Succeeded]
5 activate dynamic-template IPSUB [Succeeded]
10 authorize aaa list default [Failed]
Session Accounting: disabled
Last COA request received: never
User Profile Attribute List: None

Interface: Bundle-Ether100.100.pppoe2
Circuit ID: Unknown
Remote ID: Unknown
Type: PPPoE:PTA
IP Address: 199.1.1.2, VRF: default
Mac Address: 0019.2f43.9a38
Account-Session Id: 00000145
Nas-Port: 67110466
Username: test
Subscriber Label: 0x00000145
Created: Thu Nov 3 16:28:10 2011
State: Activated
Authentication: authenticated
Access-interface: Bundle-Ether100.100
Policy Executed:
policy-map type control subscriber sub
event Session-Start match-first [at Thu Nov 3 16:28:10 2011]
class type control subscriber CLASS do-until-failure [Succeeded]
10 activate dynamic-template TPL [Succeeded]
event Session-Activate match-first [at Thu Nov 3 16:28:31 2011]
class type control subscriber CLASS do-until-failure [Succeeded]
10 activate dynamic-template TPL [Succeeded]
20 authenticate aaa list default [Succeeded]
Session Accounting: disabled
Last COA request received: never
User Profile Attribute List: 0x500c0d24
1: service-type len= 4 value= Framed
2: sub-qos-policy-out len= 5 value= shape

Related Information

• BNG demo on YOUtube
• Using COA (Change of Authorization) tool
• BNG Configuration training from start to finish

[Vladimir Pisarenko]

But what can you say about this?

http://www.cisco.com/en/US/docs/routers/asr9000/software/asr9k_r5.1/bng/configuration/guide/b_bng_cg51xasr9k_chapter_0101.html#concept_CA2B956D03FB4533A3653BD0119AC788

I think in version 5.1.0 DHCP is enabled for IPv4 too. Is it the same scalable as for IPv6??

[xthuijs]

you're too fast after I sent my note I checked in when dhcpv4 was coming and that appeared to be 510 which I didnt realize hit cco already. I was assuming you were asking about 432.

so you're correct, v4 is in 510.

I personally havent given 510 a lot of testing yet, so I can't commnet on that. Taking dot zero releases is never my favorite strategy in case you're considering full blown deployment unless you really need the features.

regards

xander

[Carlos A. Silva]

Hi, Xander:

A while ago I asked you about the disconnect command which seems to be available on 4.3.1. I'm conducting some tests with IPoE sessions (XR4.3.2) and using the disconnect. While the command actually does what I want, which is completely destroy the session, I was wondering if you've actually tested it.

The reason I ask is: if I disconnect the session (and remember this is a test), after a bit, the CPE generates a new dhcp discover and a new ip session is built. You can see this on the BNG; now the thing is that even though everything looks OK, the data plane does not work the second time around. I cannot, for example, ping the CPE, which I'm able to do the first time it asks for dhcp, before the disconnect.

Have you seen this behavior?

TIA,

c.

[xthuijs]

hi carlos,

it sound like the disconnect for ip sessions has a bug. but we need to do some more investigation on that.

Some debugs need to be collected and at the same time I will also check some things, but probably it is best to file a TAC case for this issue. If this is a lab and you have the ability to use 4.3.2 I would want to recommend verifying that release also to see if the issue still exists there.

regards

xander

[Carlos A. Silva]

We're supposed to be working with someone from the BU in SJC at this time, not sure I should post his name here.Haven't received any feedback yet.

Anyway, one thing I can tell you for sure is, from my side of things I can't see any SMUs (whatsoever) for 4.3.2 in CCO. Not just for this issue, but at all.

[Pichet Piriyakitkosol]

Hi Xander

Could you please show me how I can define the control policy if I want to allow only the ppp sessioin from @cisco.com domain? For the other domain I will drop the session.

Thank you

Pichet

[xthuijs]

Hi Pichet, you could do that as follows, ( havent tested, typing the commands without cli):

!define how to peel the domain name from a username.

aaa attribute format DOMAIN

username-strip prefix-delimiter @

!define a class that matches that desired domain name as per interpretation rule above.

class-map type control subscriber match-any matchdomain

match domain cisco.com format DOMAIN

!define a catch all class

class-map type control subscriber PPP

match proto ppp

!define a control policy that checks the domain and authenticates the subscriber

! if the domain is not matched, the second class is hit (match-first!) and the session is disconnected without

!authentication whatsoever.

! need to add the right authen way, either full name or stripped and you may need to activate a duynamic tpl also in this event.

policy-map type control subscriber domains

event session-activate match-first

  class type control subscriber matchdomain do-until-failure

   10 authenticate aaa list default

  !

  class type control subscriber PPP do-until-failure

   10 disconnect

regards

xander

[Pichet Piriyakitkosol]

It's work! Let me try again in detail and other scenario then will update you again.

Thanks for your help.

Pichet

[Carlos A. Silva]

Hi, Xander:

Just to finish with this issue. It was a configuration issue on the ONT, customer was not aware the ONTs were configured to allow only 5 IP addresses per MAC. DHCP server assigned IPs in round robin fashion and when we hit the 6th IP address, all traffic was dropped by the ONT.

Thanks for your time.

c.

[Carlos A. Silva]

Hi, Xander:

One 'quick' question. Customer is using two VLANs/bundleE-subints on a BNG box.

VLAN A will be using BNG services and DHCP proxy, which at the moment is working fine.

VLAN B will NOT be using BNG services, but we wanted to use DHCP proxy to manage DHCP packet traffic.

Now the tricky part is that both of those VLANs terminate in the same ONT and because of an older release, the ONT will use the same MAC address on both VLANs.

When ONT asks for DHCP (at this point ONT is a traffic generator) for VLAN A (data VLAN, IPoE), everything works fine. Then, when VLAN B asks for DHCP (voice vlan, NO IPoE), we see the following message:

RP/0/RSP0/CPU0:Oct  1 09:58:53.683 : dhcpd[1068]: DHCPD PACKET: TP2505: BOOTREQUEST Drop, packet received is not on client's interface Bundle-Ether100.540

RP/0/RSP0/CPU0:Oct  1 09:58:53.683 : dhcpd[1068]: DHCPD PROXY: TP1961: DISCOVER from chaddr 0010.9400.0001 in proxy mode dropped

RP/0/RSP0/CPU0:Oct  1 09:58:53.683 : dhcpd[1068]: DHCPD PACKET: TP200: *** Packet Could not be PROCESSED ***

A few questions come to mind, but I'll start by saying that when we moved VLAN B (voice service) to a dhcp RELAY profile, everything worked.

Is this behavior expected? I mean, I would've thought that I could have the same MAC addresses as long as they are on separate logical subinterfaces and still use dhcp proxy. Does the dhcp proxy service have to be tied to a IPoE session?

(Just to complete the info, dhcp server is a cisco ios router).

Hope you can shed some light into this behavior.

TIA,

c.

[Carlos A. Silva]

Found this:

RP/0/RSP0/CPU0:router# configure
RP/0/RSP0/CPU0:router(config)# dhcp ipv4
RP/0/RSP0/CPU0:router(config-dhcpv4)# duplicate-mac-allowed
RP/0/RSP0/CPU0:router(config-dhcpv4)#

http://www.cisco.com/en/US/docs/routers/asr9000/software/asr9k_r4.3/addr_serv/command/reference/b_ipaddr_cr42asr9k_chapter_0100.html#wp2243288079

hopefully it'll fix it.

[xthuijs]

glad to hear carlos good to know it is addressed!!

xander

[xthuijs]

In releases prior to XR4.3.2 this owuld not work, you need XR432 that allows the same mac to be reused in different vlans.

you need a configuration for that also under dhcp ipv4 (mac-address-all or something like that duplicate-mac-address it may be I dunno precisely on top of my head (dont have access to a device to verify for you at this moment)

cheers

xander

[xthuijs]

Ah!! that is the command I was referring to!!

xander

[Carlos A. Silva]

Good Morning, Xander:

One quick question: is BNG funciontality supported with DHCP relay instead of DHCP proxy? I was told you are required to use the latter.

TIA,

c.