Hi group,

for a customer I design a new network.
These connect two different buildings which are connected through on
dedicated 10GB line.

There are different IP address ranges on these sides. Also there is a
requirement for one VLAN (ip address range 172.16.0.0/16) on both
sides.

In the final solution the two buildings should be connect through
eigrp because there are different IP address ranges on both sides.
Only for the migration there is a requirement for the one vlan on
borth side.

So how can I make a line as a layer 2 and layer 3 link ?

thanks

dennis

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
172.16.0.2

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.



On Jun 3, 11:10 am, dennis <ukonstan...@cityweb.de> wrote:

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

rgds

dennis

On 3 Jun., 17:52, "jseem...@gmail.com" <jseem...@gmail.com> wrote: