GRE tunnels with 3750 switches?

[pweinhold]

Hi,

We're running a network of 3750 LAN switches, and I'd like to try some GRE tunneling with OSPF. The switches do L3 routing, and OSPF/BGP, etc., can be configured on them, but I couldn't get a GRE tunnel to stay up on them. Then I thought I saw something saying that GRE tunnels were not supported on 3750 switches.

The switches don't have any physical routed interfaces, only VLAN interfaces, so for source/destination interfaces for the GRE tunnels I use the VLAN interfaces. So I'm not sure how viable it is. Has anyone had any experience with this situation?

Thanks.

[Reza Sharifi]

Hi,

GRE is not supported on the 3750s.

The General Routing Encapsulation (GRE) tunnel is not supported by the Cisco Catalyst 3750 Series Switches. Even though this feature can be configured with CLI, the packets can be neither switched by hardware, nor by software, which increases the CPU utilization.

http://www.cisco.com/en/US/products/hw/switches/ps5023/products_tech_note09186a00807213f5.shtml

Regarding your second question, since you have L3 enabled on your 3750, you can turn any of the ports to a layer-3 routed port.

HTH

Reza

[Giuseppe Larosa]

Hello Pweinhold,

GRE tunnels are not an option for C3750 as noted by Reza, you can use  dedicated SVIs and VRF lite to build segregated topologies, devices in the middle just need to have the vlan defined at layer 2 and you have the equivalent of GRE tunnels in a campus network

Hope to help

Giuseppe

[pweinhold]

Thanks to all for the replies. Rather than try to make it work with 3750s, I think we'll just purchase some low-end routers.