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I have two Cisco routers which I have configured to connect each other by static assignment of IPs as it appears in scenario 1. enter image description here

In scenario 1 each router can reach the other. In scenario 2 I have to put layer 3 switch in between, which is configured with vlan 433 in both interface sides. Now the routers can’t reach each other. What commands I need to do in both router to make them able to reach each other?

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Layer 3 switches can act in layer 2 only mode... just make sure the vlan is created on the switch and both ports connected to your routers are in that vlan. – cpt_fink Mar 28 '13 at 3:50
Something is wrong. There is no reason the two routers wouldn't be able to reach each other if the ports are in access mode and in the same VLAN. (Did you wait at least 30 seconds? Are the ports in access mode? Are they in the same VLAN? Did the port lights come on?) – David Schwartz Apr 11 '13 at 6:04

A layer 3 switch is a de facto router. Both switch ports have to be configured to the same VLAN, else they won't be able to see each other. Look at the switch's CAM and ARP tables to ensure they're on the expected ports and VLANs.

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