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New Member

Network Interconnection Problem

I have a problem interconnecting three networks (Please see attached files). Network X,Y and Z are different networks with different VTP domains. The core switch will be the 3550-24-SMI (Device D). Device C and D are connected by means of a WS-G5484 Short wavelenght GBIC. And device B and C is also connected by means of WS-G5484. Connection from device A and B is by WS-G5486 (long wavelenght). In between B and C, it is trunk. The same with C and D. Device D and E will be connected by using a WS-G5484 GBIC Module.How could I connect the network? Please help.

  • Other Network Infrastructure Subjects

Re: Network Interconnection Problem

If I am correct your question is how to attach switch E to the existing network?

Simplest solution would be to define a new vlan on the core and put the corresponding GBIC-slot into this vlan as an access port (NO trunking).

int vlan xx

ip address 192.168.13.x /24

int gig YY

no ip address

swi mode access

swi acc vlan xx


Then you can use static routing or a routing protocol to direct users on the 192.168.13 network to your existing core as the L3 next-hop.



New Member

Re: Network Interconnection Problem

Hello Leo!

I am very much thankful for your response. I will try this suggestion tomorrow. I will update you of the outcome.

As for the other link,device A(6509) and B (3550). This is my other concern. device B,C, and D are in one network. And the core switch is device D. Device D will be the central point of Control for the 3 networks. Just this afternoon, I connected the physical link from A to B using long wavelenght GBICs (WS-G5486). The link is now active, but I don't know how to start with the configuration so that VLAN 2 on A and VLAN 2 on D and E network could see each other.Again, thank you very much for your response I appreciate it.

Re: Network Interconnection Problem

It also seems as if the three networks are not under the same adminstration. Therefore, I assume that they are also not in the same VTP domain.

You must be aware of this when you are making interconnections. You could for example connect vlan2 on network X to vlan 200 on network Y. This will work perfectly as long as you do not set up vlan trunks between the different networks.

Internetwork traffic can then be routed over the interconnected vlans.

When the networks are all under your administration, you must keep in mind that you should set up a consistent relation between vlan-id's and IP networks. In fact, that is what I missed in this case. This setup boils down to creating one big vtp domain. You would then have something like net 172.18 on vlan 18 for network X, Y and Z, and another unique vlan-id per other IP range.

Hope this helps you along,


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