Using Routed Access Layer with CatOS

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Feb 19th, 2009
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Is it possible to configure closet switches (3750's) to use L3 Routed Access when connected to 6509 core switches running CatOS? I've found documentation on setting up Routed access, but nothing about how to do it with CatOS.

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Jon Marshall Thu, 02/19/2009 - 05:47
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You can but CatOS has no concept of a routed port ie. "no switchport".

So on your 3750 you could configure

int fa0/1

no switchport

ip address

On the 6500 you would need to configure

int vlan 10

ip address

and then put the port that the 3750 connects to into vlan 10.

Make sure that no other ports are in vlan 10. For each routed connection from a 3750 you would need to use a separate subnet and vlan on the 6500.

This is as close as you can get to a routed connection with CatOS.


rdotson Thu, 02/19/2009 - 06:38
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Thank you Jon. We will be converting the 6509's to IOS eventually, but wanted to test using Routed Access and try to get rid of STP.


Joseph W. Doherty Thu, 02/19/2009 - 06:40
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Another approach would be to have your 3750 share access on the same 6509 hosted vlan, a switched core approach. Each 3750 would see all the other 3750s as routers, a dynamic routing protocol would make known to each 3750 what edge subnets are on the other 3750s.

You also mentioned 6509 swithes, plural? If so, each 6509 could host an independent vlan subnet shared by all the 3750s. Avoids the need to L2 between 6509s.

One disadvantage of sharing vlan segments, routers might not see down link for lost connectivity and may need to depend on routing protocol seeing lost peer in some situations. However, if you can run (3750) cross stack and (6509) cross card Etherchannel, individual down links shouln't be an issue.


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