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New Member

3550 question


I have two sites with switched LAN's using (soon) 3550's as layer 3 switches. Each site has its own vtp domain. Between each site is a 100mb LAN extension which at the moment is connected by routers. I want to move this to my 3550's to improve speed between the two sites. What I was thinking of doing was putting an IP address with a 30bit mask on a switchport on each 3550 and then joining them together. I have never tried this in a live environment, will this work ok, and with the two LAN's being on different VTP domains, will this prevent any conflicts between the switches in terms of VLAN configuration. I would just like clarification as this could quite easily go wrong Im sure. Any advice would be greatly appreciated


Re: 3550 question

In my opion this should work. As long as you configure the ports as access-ports and not as trunks. Having different vtp domains will prohibit any conflicts.

It is advisable to disable spanning tree on the ports and not to use vlan1 for the link. This is because vlan1 is used to carry vtp data and bpdu's for MST according to 802.1q. You do not want this traffic on the link.

Also you will need a cross-cables to connect the switch instead of a router as you had already thought of yourself naturally!


New Member

Re: 3550 question


Thanks for reply .... just one Q .... If I configure the ports connecting the 3550's as routed ports, will they not be just like standard router ports doing layer 3 switching .. .. ie they wont be assigned to any vlan or configured as access or trunk ports, I may be confused but please put me straight on this.


Re: 3550 question

As I previously stated you HAVE to configure them as access-ports.

By assigning them to a unique vlan you create a kind of router interface port.

Without assigning them to a vlan, they are in vlan1 which is not ideal.

Writing this, I assume that you will be using one ip subnet for the routed link. You said that you would use a 30 bit mask for this. That's OK.

Layer 3 switching must in this case be seen as a faster equivalent of routing. Functionally there is no difference.

New Member

Re: 3550 question

Thanks for reply .... I now do understand

Best regards

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