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Connecting two LAN Networks

Hi Folks,

I have this complicated scenerio, and really need someone's help.

The new network is:

(2) 6509 Switches with layer 3 blade(5) 3

(5) Gigabit Stack swtiches for Server farm 1. The subnet will be VLAN 20

(5) Gigable Stack for Server farm 2. The subnet will be VLAN


(1) 4006 for IDF will be on VLAN 85, subnet

(1) 4006 for the same IDF, but will be on VLAN 86, subnet

1st 6509 will be root bridge for vlan 85 to reach vlan 20, 2nd 6509 will be root bridge for vlan 85 to reach vlan 30

2nd 6509 will be a root bridge for vlan 86 to reach

vlan 30,

1st 6509 will be a root bridge for vlan 85 to reach vlan 20.

On top, I will also do HSRP for layer 3 redundancy.

To add the complexity, customer has an exisiting network and want to migrate slowly by connecting their existing network to this new network. Customer currently has

(2) Catalyst 4000 Server Farm switches and

(2) 7500 router with tons of IDF swithes and they reach the server farm switches via 7500 routers.

1st 4006 has subnet same as we will use for the new network, and

2nd 4006 has subnet again same for the new server farms. No vlans are used.

(2) 7500 router connects to both switch to support HSRP. 7500 routers are doing both LAN and WAN traffic. Eventually 7500 will only be used for WAN after the migration. One thing I could do to connect their 4006 switch to my 3500 server farm switches. All I need to make sure that to assign a different ip addresses on 6509 switches from the same existing subnets which are and Meaning if the customer is using 192.

168.20.1 (Virtual ip address for HSRP) and an as physical address on 1st 7507 and (Virtual IP address for HSRP), and as physical addresses on the 2nd 7507. I could use the different addresses from the same subnets for my 6509 backbone switches let say, (virtual ip address, and and 254 as a physical ip addresses. Luckily only server farm subnets can not be changed. For the floors' IDFs they will be using all new subnets which will not conflict with their exisiting subnets. Now, 6509 switches will be connecting to the new IDF switches. Now, traffic from the 6509 (new network) and traffic from the 7500 routers should be able to reach the server which are currently on 4006 switches but slowly will be moved to 3500 gigastack switches.

If I connect their 4000 switches to the new 3500 switches, both are layer2, and the server can only default gateway to either reach 7500 router or 6509 router switch. Doesn't seem to work. The only solution, I could think of is to connect their 7500 routers to my 6509 swtiches as a layer 3 connectivitly. Customer doesn't want to go with this option. Is there anything which can allow traffic from both networks to reach the server farms without connecting 7500 to 6500.




Re: Connecting two LAN Networks

Why not interconnect the old-and new workgroup- and server segments and let the routing protocol sort it all out? During the migration you could change the default GW on the machines to match the new configuration.

When your hosts and clients are all running on the new network, change over the external routes and other stuff as a last step.

In this way, you will allways have a backdoor.