Cisco 1721 router with Ethernet interface card

[husseinmuneer]

Dear all,

I have cisco 1721 router so I installed an ethernet interface card so when I make show run I found that there is a fast ethernet 0 and ethernet 0 (which I installed) so i wand to make subinfaces of the etheernet 0 but I can't.

I tried to make encapsulation dot.1q but it doesn't accept it.

Is Ethernet0 supported to generate subinterfaces?

regards.

[lgijssel]

As far as I know, 10Mb interfaces never support subinterfaces. This is because neither ISL or dot1Q can be configured on them.

http://www.cisco.com/en/US/products/hw/routers/ps221/products_data_sheet09186a0080088714.html

Cisco is never too explicit about what their products cannot do but at least the link above provides some info.

regards,

Leo

[Peter Paluch]

Hi Leo,

As a matter of fact, the built-in 10Mbps Ethernet interfaces in 2610 series routers do support 802.1Q subinterfaces in recent IOS versions (I am not sure about the exact starting version but I am sure about the 12.3 and last 12.2T versions). We use these routers regularly in our labs during NetAcad classes. But you are right, the 802.1Q support was not always available on the 10Mbps interfaces, and I am afraid that it may actually not be supported at all on additional WIC or NM Ethernet routed port cards.

Best regards,

Peter

[lgijssel]

Hi Peter,

It takes a crack like you to exactly point out the details.

I knew there were a few exceptions but my understanding was that this was more an error in the software than a feature.

Backward compatabilty (with other vendors) is what also counted for this. ISL was introduced on fast ethernet.

However, as far as the WIC-1ENET modules are concerned, they are indeed not supporting any of the forementioned options.

regards,

Leo