Http problem with 4500x used as switch L2

[Jean-Paul FANDOUX]

Hello

I have actually a 4500X with ipbase, but used only as switch (03.06.03.E)

the switch provide few Vlan input and output for ex 50,51 and 52.

50 and 51 provide from PPPoE customer to BNG (asr9k), and 52 provide from IPOE (DHCP) customer alsays to asr9k.

Once connected, customers in vlan 50 and 51 can ping, http etc...

But customers on vlan 52 (DHCP) can ping every url (DNS work well) but cannot http (on url).

When I move same config to a 3750G switch, everything work well (ie. all VLAN).

can someone tell me where is the problem  on 4500X?

Here is the interface config:

!
interface TenGigabitEthernet1/14
 description >>> INPUT FROM TELCO<<<
 switchport trunk allowed vlan 50-52
 switchport mode trunk
!
interface TenGigabitEthernet1/15
 description >>> OUTPUT TO ASR9001 <<<
 switchport trunk allowed vlan 50-52
 switchport mode trunk
!

Thanks for any help

Jean

[xthuijs]

hi JP, this smells like a fragmentation issue, due to an additional pppoe header of 8 bytes and standard mtu size, you could end up with a 1508 byte packet that somewhere might get dropped especially if a DF bit is set which some http servers do.

you could try a ping from a device at 1508 bytes with the df set (via extended ping) to prove that theory.

if that is the case, mtu tune, or an mss adjust could be an option here.

cheers!

xander