7206VX with PPPoE throughput slow

Unanswered Question
Jan 2nd, 2009

I have been tasked with setting up our first PPPoE DSL connection. We have it up and running, but the speeds seem to be rather slow, and would like someone to review the config and see if I am missing something that would improve the overall speed of the pppoe connections. During download tests, we found that we would drop from 12MB(standard ethernet) to 4.5MB (PPPoE). So any help would be appreciated. Here is relevant information:

7206vxr with a NPE-G1 Card

Version: c7200-advipservicesk9_li-mz.124-20.T1

Relevant Configuration information:

bba-group pppoe global

virtual-template 41

sessions per-mac limit 2

interface Loopback41

ip address 192.168.41.1 255.255.255.255

interface GigabitEthernet0/2

no ip address

duplex auto

speed auto

media-type rj45

no negotiation auto

interface GigabitEthernet0/2.2

description DSL-Data Traffic

encapsulation dot1Q 4

pppoe enable group global

interface Virtual-Template41

description New Subnet 41 Behind Occam

mtu 1454

ip unnumbered Loopback41

no ip route-cache cef

no ip route-cache

ip tcp adjust-mss 1414

no logging event link-status

load-interval 30

no peer default ip address

ppp authentication pap

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Giuseppe Larosa Sat, 01/03/2009 - 06:58

Hello Todd,

if there is an ATM cloud in the middle the ATM SAR (Segmentation and Reassembly) required to create ATM cells for each PPPoE PDU can reduce the performance for a single session.

May you describe the whole network from DSL to C7206VXR ?

Hope to help

Giuseppe

tadamson Mon, 01/05/2009 - 13:41

The current setup is:

DSL Modem

|

PPPoA

|

Occam

|

PPPoE

|

Cisco 7206

We currently have a couple of old pieces of equipment that the DSL modems currently run through via PPPoA and work fine. But we are now moving to the Occam for more functionality and we were hoping to minimize the transition by not having to touch each remote modem. That's the reason for the PPPoA into PPPoE.

So is this transition the cause for the drop in speed?

Todd

tadamson Mon, 01/05/2009 - 14:39

On an additional note, if we plug a laptop into a directly connected port on the 7206 that are both configured for PPPoE, the speeds are slowed down as well.

Thoughts....

Giuseppe Larosa Tue, 01/06/2009 - 02:16

Hello Todd,

in the virtual-template config you have disabled CEF and fast switching

no ip route-cache cef

no ip route-cache

I would try to reenable them (this should have an impact on scalability)

see for example

http://www.cisco.com/en/US/docs/ios/bbdsl/configuration/guide/bba_pppoe_baa_ps6441_TSD_Products_Configuration_Guide_Chapter.html#wp1065627

note2:

you have PPPoA on the DSL to the Occam, then the OCCAM have a PPPoE session with the C7206.

the OCCAM is an ip dslam

see

http://www.occamnetworks.com/pdf/CiscoSvcFlxOccam.pdf

I wonder if the PPPoE session is needed from occam to the c7206 or it could be a simple IP connection.

Hope to help

Giuseppe

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