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Bri
New Member

VLAN problem over E1 link

Dear Experts,

I have configured multiple VLANs over one network.

Core Switch to Access switch are configured with trunk to trunk connectivity using dot1q and native vlan 10.

If these switches are connected back to back with each other, everything is fine.

Now, the problem is, if the Coreswitch and Access switch are connected via E1 (2MBPS) the computers(connected to access switch) can no longer access internet and no email. Both trunk ports are experiencing collisions even if there's less than 10 users. Anyways, phones are working fine.

Taking also these users to native VLAN everything is fine.

Appreciate if anyone of you experts have encountered these kind of problem? Or do you have any suggestions on how I can resolve it?

8 REPLIES
Hall of Fame Super Bronze

Re: VLAN problem over E1 link

Now, the problem is, if the Coreswitch and Access switch are connected via E1 (2MBPS) the computers(connected to access switch) can no longer access internet and no email.

Please provide a network diagram from your current network. Are you saying the switches are directly connected to the service provider? Do you have a router between these switches?

__

Edison.

Bri
New Member

Re: VLAN problem over E1 link

Hi Ed,

Just a correction with what I said native vlan is 10, 17(data), 517(voice).

Attached is a simple diagram and config of both coreswitch and access switch.

Thanks for the reply.

Regards,

Brian

Hall of Fame Super Bronze

Re: VLAN problem over E1 link

What device provides the connectivity for the E1 connection?

The switches do not have an E1 interface so you must have a device servicing this connection.

I don't think you can carry 802.1q over the E1.

You need to create new 'non-overlapping' subnets in the 3560E and route them over to the 3750 core. You also need to route traffic from the 3750 core to the 3560E.

If you are not sure how to complete the task, I recommend getting some outside help.

__

Edison.

Bri
New Member

Re: VLAN problem over E1 link

Hi Ed,

I'm using RAD-RIC E1.....Ethernet to E1 converter.

What you mean by the non-overlapping?

Thanks for the reply.

Brian

Hall of Fame Super Bronze

Re: VLAN problem over E1 link

I'm not familiar with the RAD-RIC E1.

Are you able to see the switches via CDP?

By 'non-overlapping', I'm referring to create an IP subnet on the remote location that does not conflict with your Core location and then route the subnet with the switches.

__

Edison.

Hall of Fame Super Silver

Re: VLAN problem over E1 link

Hello Brian,

I've given a look at www.rad.com they say they support Ethernet and Vlans.

I've only one doubt : an 802.1Q frame is still an ethernet frame but with an increased size of 4 bytes.

You say that phones are fine: but phones use small packets for the RTP streams.

And phones are in non a native vlan 517, so vlans are supported.

I'm afraid the converter has troubles to carry an 802.1Q that contains an IP packet of 1500 bytes (a baby giant 1500+18+4 = 1522 bytes).

I would suggest you to perform an MTU check on the converter by using ping of increasing size.

If so you should think to reduce ip mtu on SVI vlan interfaces and on the PCs

Hope to help

Giuseppe

Hall of Fame Super Silver

Re: VLAN problem over E1 link

Hello Brian,

you say that if PC users are in the native vlan they work, but in this case no 802.1Q tag is added (native vlan is untagged) so this confirms an MTU problem with tagged frames

Hope to help

Giuseppe

Bronze

Re: VLAN problem over E1 link

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