PPPoE DSL Problems, probably MTU or MSS - ALICE

Unanswered Question
May 20th, 2010

Hello,

I'm trying to use a cisco 887 router for a domestic PPPoE DSL (italian ALICE DSL).

I can ping public host but I can't surf. Only a few web site can be reached and very slowly, i checked dns and name resolution is ok.

No problem with my domestic router.

Can you please tell me a right PPPoE configuration for my router?

I tried several MTU and MSS value but without success.

(do I have to set mtu or ip mtu?).

Is there anybody can help me?

Thank you very much

Johnny


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l.buschi Thu, 05/20/2010 - 18:20

My configuration is the following

interface Vlan1

mtu 1452

ip address 10.240.4.1 255.255.255.0

no ip redirects

no ip unreachables

no ip proxy-arp

ip mtu 1442

ip flow ingress

ip nat inside

ip virtual-reassembly

ip tcp adjust-mss 1394

interface ATM0

no ip address

no ip redirects

no ip unreachables

no ip proxy-arp

ip flow ingress

no atm ilmi-keepalive

pvc 8/35

  encapsulation aal5snap

  pppoe-client dial-pool-number 1

interface Dialer0

description $FW_OUTSIDE$

mtu 1442

ip address negotiated

no ip redirects

no ip unreachables

no ip proxy-arp

ip flow ingress

ip nat outside

ip virtual-reassembly

encapsulation ppp

ip tcp adjust-mss 1394

dialer pool 1

dialer-group 1

ppp authentication chap pap callin

ppp chap hostname aliceadsl

ppp chap password 7 155841464E60616E6279

ppp pap sent-username aliceadsl password 7 024C4E11414C456B0604

ppp ipcp dns request

Paolo Bevilacqua Fri, 05/21/2010 - 12:52

Configure:

interface Vlan1

default mtu

default ip mtu

ip flow ingress

ip tcp adjust-mss 1452

interface  ATM0

default ip address

default ip redirects

default ip unreachables

default ip proxy-arp

no ip flow ingress

no atm ilmi-keepalive

pvc  8/35

  encapsulation aal5snap

  pppoe-client  dial-pool-number 1

interface  Dialer0

description $FW_OUTSIDE$

mtu 1492

no ip tcp adjust-mss 1394

l.buschi Mon, 05/24/2010 - 06:36

Hi Paolo,

Thank you very much.

I can see a little number of web site, and most of allonly in the first page.

The router still doesn't work, while my domestic router works perfectly.

The value I used are the ones you suggested in the answer to my post but they don't work.

I also tried to chagnge IOS firmware without any  success.

can you help me?

Thanks

JOhnny

l.buschi Mon, 05/24/2010 - 07:11

!

interface ATM0

no ip address

ip flow ingress

no atm ilmi-keepalive

pvc 8/35

  encapsulation aal5snap

  pppoe-client dial-pool-number 1

!

!

interface Vlan1

ip address 10.240.4.1 255.255.255.0

no ip redirects

no ip unreachables

no ip proxy-arp

ip flow ingress

ip nat inside

ip inspect FW in

ip virtual-reassembly

ip tcp adjust-mss 1452

!

!

interface Dialer0

description $FW_OUTSIDE$

mtu 1492

ip address negotiated

ip flow ingress

ip nat outside

ip virtual-reassembly

encapsulation ppp

dialer pool 1

dialer-group 1

ppp authentication chap pap callin

ppp chap hostname aliceadsl

ppp chap password 7 155841464E60616E6279

ppp pap sent-username aliceadsl password 7 024C4E11414C456B0604

ppp ipcp dns request

!

!

dialer-list 1 protocol ip permit

Paolo Bevilacqua Mon, 05/24/2010 - 07:23

try:

interface vlan1

     no ip virtual-reassembly

     no ip inspect FW in

     no ip flow ingress


interface dialer0

     no ip virtual-reassembly

     no ip flow ingress

     ppp ipcp default route

And remove any other default route you may have.

l.buschi Mon, 05/24/2010 - 07:30

Thank you paolo,

in a couple of hours I'll try the new configuration.

as regards IP INSPECT FW IN i tried yesterday to disable any firewall but without any success (that configuration line is a result of the last tests).

I didn't try to remove default routes using ipcp default route and to disable ip virtual-reassembly.

Let's see tonight if it will be ok (I'm testing the configuration in my home adsl connection).

I thank you very much

Johnny

l.buschi Mon, 05/24/2010 - 11:55

It doesn't work.

I open only a few web sites, very slowly.

Ping and name resolution works correctly.

If I use the router to connect as a ezvpn client to a central site with split tunnel, I have no problem to open web internal pages (printer gui, intranet web site and so on), i can ping and dns outside but i have the same issues with web external sites.

I noticed that DSL interface ATM0 shows capacity used 100%

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