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New Member

Cisco 6500's and PC not able to surfing the internet

Hi all,

My setup is :

SW3 Cisco 6509 Switch -> Vlan Trunk (through LAN Extention) -> SW1 Cisco 6513 -> Etherchannel Vlan Trunk -> SW2 Cisco 6513 -> firewall (fortigate) -> internet...

The PC can ping from SW3 across to the internet without any issues.

Although, when trying to surf the internet, it times out. The firewall is not blocking port 80 what so ever...

The IE window shows found website, waiting for reply.

Does anyone have any idea what this could be? Why it can ping and not surf?

A PC on SW1 or SW2 can surf the net without issues....

The LAN extension between SW1 and SW3 is setup on both sides (the interface config) as trunk ports allowed all vlans.

5 REPLIES

Re: Cisco 6500's and PC not able to surfing the internet

It look like a MTU problem. Some MPLS Lanex provider dont allow space for the VLAN tag. Got 1 link like that on my network.

Can a 1500 bytes ping go tru the link?

New Member

Re: Cisco 6500's and PC not able to surfing the internet

The carrier says they are set for 1514bytes MTU's.

The carrier we deal with for the LAN extension uses Alcatel (7750) setup as Layer 2 switch link.

Is there anything I can look at on my cisco switches (in the config or logs) that would show me dropped frames due to sizes or something?

Re: Cisco 6500's and PC not able to surfing the internet

Do a ping

from your pc connected on the SW3:

ping -l 1500 www.google.com

If it dont work, reduce the packet size.

But this is realy your problem, the maximum size of a tagged frame si 1522.

1518 is the maximum size of ethernet non tagged frame

New Member

Re: Cisco 6500's and PC not able to surfing the internet

from SW3 1468 works, but anything above does not.

From a PC on SW1, i can ping up to 1472

what does all this mean?

New Member

Re: Cisco 6500's and PC not able to surfing the internet

Found the problem...

The carrier we use uses a Alcatel switch and both switch ports are setup exactly like that... switchports...

We, on the other hand, have the Lan Extension ports on both switch configured as trunk ports.... See the problem?

So to test this, I setup for ports on the 6500's to switchport access vlan 104 and the pc's can now surf the internet.

The problem is that we cannot assign multiple vlans to an access port, so our phones on SW3 are not working...

We are trying to have the carrier change the ports on there Alcatel to trunk ports 802.1q until they switch our service from switched lan extension to ethernet private link...

Thanks for all the help...

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