Re: L2protocol-Tunneling Sanity Check

Joe,

Seems to work for me as you expected it to ... I've included the images
so you can compare. Same setup as you described (no l2protocol tunnel
command on the inter-switch link).

Paul

Rack1SW1#sh ver | inc flash:
System image file is "flash:c3560-advipservicesk9-mz.122-46.SE.bin"
Rack1SW1#sh l2protocol-tunnel | inc cdp
Fa0/1 cdp ---- ----
6 6 0
Rack1SW1#

Rack1SW3#sh ver | inc flash:
System image file is "flash:/c3550-ipservicesk9-mz.122-44.SE6.bin"
Rack1SW3#sh l2protocol-tunnel | inc cdp
Fa0/5 cdp ---- ---- 6
6 0
Rack1SW3#

Rack1R1#sh cdp nei
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
                   S - Switch, H - Host, I - IGMP, r - Repeater

Device ID Local Intrfce Holdtme Capability Platform Port ID
Rack1R5 Fas 0/0 126 R S I 1841 Fas 0/1

Rack1R5#sh cdp nei
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
                   S - Switch, H - Host, I - IGMP, r - Repeater

Device ID Local Intrfce Holdtme Capability Platform Port ID
Rack1R1 Fas 0/1 159 R S I 3725 Fas 0/0

On 09/12/2011 00:43, Joe Astorino wrote:
> Hey everybody, I could use some assistance validating my sanity in this
> situation. First, the topology
>
> R1 --- Cat1---Cat2---R2
>
> I am attempting to configure l2protocol-tunneling alone (without Q-Q at
> all) such that R1 and R2 see each other as directly connected in CDP. I
> thought for sure I had this configuration correct, but it wouldn't work.
> Cat1 is a 3560 and Cat2 is a 3550. I am noticing behavior on the 3550 that
> is not happening on the 3560. Note there are no trunks and every port is an
> access port in VLAN 1.
>
> My original thought was this: configure "no cdp enable" and
> "l2protocol-tunnel cdp" on ONLY the edge ports of Cat1 and Cat2 that
> connect to the routers. When I do this I see Cat1 encapsulating frames in
> "show l2protocol-tunnel" but Cat2 never shows any decapsulated or
> encapsulated frames. When R1 sends a CDP frame, Cat1 should intercept it
> due to the l2protocol-tunnel CDP command, and rewrite the destination MAC
> to the proprietary Cisco MAC used for l2protocol-tunneling. That frame
> should then be sent out the cross switch link to Cat2. Cat2 should see
> that it also has "l2protocol-tunnel cdp" configured on the edge port facing
> R2 and rewrite the destination MAC back to the CDP multicast address and
> forward to R2. The same should happen the other way.
>
> Again, the 3560 shows frames encapsulated but the 3550 does not yet they
> have an identical configuration. First this led me to believe maybe an IOS
> bug in the 3550 12.2(44SE6) so I tried another version with the same
> results. Every example I can find out there usually only does l2pt on a
> single switch or if spanning multiple switches they are combining with
> Q-Q. I understand those concepts fine, but I am not looking to do Q-Q in
> this example. I don't have another 3560 on hand to test with.
>
> I started second guessing myself and thinking I needed "l2protocol-tunnel
> cdp" on the edge ports AND the cross switch links on both ends. When I do
> that, it actually works but I don't think it works for the right reasons.
> Ultimately, in this type of setup can anybody confirm weather you need
> "l2protocol-tunnel" on ALL ports between the source and destination or just
> on the edge ports.

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Received on Fri Dec 09 2011 - 01:13:59 ART