Design Question - On physikal Line as Layer 2/3

Is the 10 GB link an ethernet handoff? If so connect it to a switch on either side, and set up dot1q trunking. This will allow you to put the VLAN supporing 172.16.0.0/16 on both sides. This should also incidentally solve your routing issue. Here's some sample config with an explanation:

SITE A:

LAYER2/3 SWITCH:

vlan 16,10

interface gi 1/1 description this is where you plug in the 10 gig link. of course you'd want a 10 gig switchport switchport switchport mode trunk switchport trunk allowed 16

interface vlan 16 description this is your shared vlan ip address 172.16.0.1 255.255.0.0

interface vlan 10 description this is a sample "site a only" vlan ip address 10.10.0.0 255.255.0.0

router eigrp 100 network 172.16.0.0 network 10.0.0.0 no auto-summary

SITE B:

LAYER 2/3 SWITCH:

vlan 16,20

interface gi 1/1 description this is where you plug in the 10 gig link. of course you'd want a 10 gig switchport switchport switchport mode trunk switchport trunk allowed 16

interface vlan 16 description this is your shared vlan ip address 172.16.0.2 255.255.0.0

interface vlan 20 description this is a sample "site b only" vlan ip address 10.20.0.0 255.255.0.0

router eigrp 100 network 172.16.0.0 network 10.0.0.0 no auto-summary

In this setup, any intra-vlan-16 traffic will be switched. I'd recommend devices at site A have a gateway of 172.16.0.1, and at Site B a gateway of 172.16.0.2 to cut down on crosstalk.

Routing will be handled by virtue of EIGRP using VLAN 16 as a transit medium between the switches. So for example at Site A, if you were to sh IP route 10.20.0.0, you'd see this site is accessible via router

So essentially your line will be a layer 2 link, using that shared VLAN to transit traffic.

Once you've eliminated that shared VLAN, you can switch to routed interfaces if you like.

Thank you for the detailed explanation. This solution is what I need....

rgds

dennis