SFP Port

[willie.jennings]

I have a Catalyst 3560-CX Series and a 2921 Integrated Service Router and I'm looking to connect them via the GigabitEthernet SFP port on both.

Do I configure the SFP GE 0/1 on the router with the same IP scheme that I've placed on the switch?  Is it configured when the Ethernet is configured for GE 0/1?

[Jon Marshall]

Not sure what you are asking.

You will need a common subnet between the two devices, if you are using a L3 routed port on the 3560 then just use a /30 subnet so you have an IP address for each end.

If this is not what you are asking can you clarify.

Jon

[Julio E. Moisa]

Hi

Could you please provide more details, not sure if you want to change the config from a normal Ethernet port to a SFP port, is that correct?

[willie.jennings]

Julio,

I want to thank all of you for responding.  Once I configured the switch, the Catalyst 3560 Switch and the 2921 ISR did link up as it was communicating.  But due to the fact that I had a VLAN already configured on the router, the needed IP address I configured for the G0/1 port gave me an overlapping error.

I need to connect the two via SFP because of the distance between the two items.

Again the link between the two has been established, but they won't communicate through the connection.

[Julio E. Moisa]

Hi

Yes, it will generate a overlaps error because you want to use 2 ip addresses over the same network segment. 

Please correct me if Im understanding wrong,

You want to connect 2 interface over the same vlan from the switch to the router?

[willie.jennings]

You are correct.  About 4 items needs to be connected to the switch with the same ip scheme of one of the configured VLANS on the router.  I had to upgrade to a Gigabit SFP for connection on both ends because the fiber being used is passing video and data which two 10/100MB switches couldn't handle what was being transmitted without degradation.

[Julio E. Moisa]

Thank you

You can connect 2 switchports to 2 router ports under the same vlan and network segment using BVI. 

Please check this link:

http://www.cisco.com/c/en/us/support/docs/lan-switching/integrated-routing-bridging-irb/200650-Understanding-Bridge-Virtual-Interface.html

For example:

Switch

vlan 100

interface vlan 100
ip add 192.168.100.1 255.255.255.0
no shutdown

interface fa0/1
switchport access vlan 100
switchport mode access
no shut 

interface fa0/2
switchport access vlan 100
switchport mode access
no shut 

Router

bridge irb
bridge 100 protocol ieee
bridge 100 route ip

interface g0/0
no ip address
bridge-group 100

interface g0/1
no ip address
bridge-group 100

interface BVI 100
ip add 192.168.100.2 255.255.255.0
no shutdown

:-)

[willie.jennings]

I think the BDI answers the question.

[Julio E. Moisa]

Great! 

:-)

[willie.jennings]

What is the best method for connecting the two?  I know changing the IP Scheme of the switch and the components connected to it may work as long as I keep the same subnet and possibly the Gateway to match the VLAN.

Am I correct in this statement?

[Joseph W. Doherty]

As the other posters have already noted, additional detail is needed.

There are several way the two devices could be configured to communicate.

At some level, usually the router will be configured to "share" a network with the L3 switch.

Perhaps the most common configuration would be to configure a 2921 built-in port with and IP, usually a /30 (or perhaps a /31), and configure the port on the 3560 as a "routed" port, also with an IP.  This to make a point-to-point link between the two devices.

Again, there are multiple alternatives.  For example, the L3 switch might just connect the port to the router as just a L2 port.  The L3 switch, might connect an access port to the router using a SVI.  The L3 switch might also use a trunk port to the router, and the router use subinterfaces.

More unusual would be defining the router port as a bridged port (I think that's still possible on a 29xx).