[c-nsp] Forwarding traffic to "transparent" device

Cyrill Malevanov cm at n-home.ru
Thu Feb 25 16:11:36 EST 2010

On Feb 25, 2010, at 12:56 AM, Pavel Dimow wrote:

> Hi,
> as I am not native english speaker I don't know how to name my problem
> but I will try to give as much details as possible.
> Here it is, I have Cisco 7600 wich is core switch, and it have one
> uplink to our edge router (it is SVI interface). Now, I would like to
> insert
> a transparent cache engine. That would not be a problem, except that
> connection between edge and core is fiber and
> transparent device has only a copper ports. I know that I can buy
> media converters, but what I would really like before
> is to connect cache to core and forward all (to and from internet) via
> cache and then back to core and so on.
> Something like this:
> ------------
> | EDGE |
> ------------
>      |
>   --|--
>   | C |
>   | O |-------CACHE
>   | R |--------
>   | E |
>   -----
> Is this possible at all, and is there are any other solutions?

vlan 20 is looking at edge from the core. You use vlan 20 on edge, vlan enters the fiber port from edge, then you delete int vlan 20. Vlan 20 then should go to cache through access port. Then you receive that vlan from the cache, but name it vlan 30. Receive it via access port and move your core ip address from int vlan 20 to int vlan 30.

Port 1 - edge.
it was sw mo trunk, sw tr al vl 20
And you have int vlan 20 / ip addr

Now port1 - edge. 
sw mo tr
sw tr al vl 20

port2 - traffic from edge to cache
sw mo ac
sw ac vl 20

port 3 - traffic from cache to core.
sw mo ac
sw ac vl 30

And int vlan 30
ip addr

When you route 0/0 points to, traffic goes this way:
what is an arp of send broadcast
broadcast goes out via vlan 30, out from core via vlan 30 port 3, through cache, enters core as vlan 20 into port2, goes out as vlan20 from port1. 
ARP reply goes to port1, vlan 20. Then it looking up mac-table - where is maс from vlan20 had been seen? port2. Then traffic goes out from port2, vlan 20, through cache and then enters vlan 30 into port 3. Wow! that's my mac in that vlan.

> Thank you.
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