Installing Cisco 1720 Ehternet Interfaces

rajotico used Ask the Experts™
This is my first Cisco router. I installed the first card and configured it, the router named that itnerface  FastEthernet0. I then installed the second network card which is the exact same model. I can't configure the second card because the router gave both cards the same name. I tried the port notation (ethernet0/1, 0/0) but that didn't work. After rebooting the router,  the intial boot sequence shows two fastehternet0  cards one with the line "sate changed to up" and the other with the line "state changed to down". When I  enter: show running-config  I am only shown the configuration for the first card.
Then I enter:
           confi terminal
            interface fastethernet0  
That gives access to the first card again. How Do I access my second card. Again I already tried the fastetehrnet0/0 notation to no effect. I know this is a very simpel question, I hope someone can help. Thanks.
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TodosNetwork Engineer

Hi Rajotico,

I believe the expension slot of the 1720 is a WAN slot. The ethernet module supported in this WAN slot is a 10baseT ethernet card.

You should be able to configure it addressing it as ethernet 0.

So your commands :

Router#configure terminal
Router(config)#interface ethernet 0

See this link for more information :

Good luck.



did that, as I explained on the question statement:
Router(config)#interface ethernet 0 --> gets me to the first card. The second card is only listed while the router is booting up. and is also named interface ethernet 0. How do I access it??????

Please run the following and provide the output:

Router#sh int

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Router#sh int : shows the configuration for FastEthernet0, but I have two cards, and as far as I can tell both have the same name; So it could be either one of them at this point. Both cards have a green light in the rear panel, so I know they're properly installed.
Anybody has any idea what could be wrong...?

I've seen sub interfaces on Cisco serial ports - same on Ethernet?

int 0.0
int 0.1
int 0.2


FastEthernet would be the 10/100 card, Ethernet would be the 10baseT card
A couple of things to look at:

- When it intially boots up, you say that one inteface changes state to up, the other interface goes down.  Can you provide the lines echoed to the console of both the up and down

12w4d: %LINK-5-CHANGED: Interface FastEthernet0, changed state to down
12w4d: %LINK-5-CHANGED: Interface FastEthernet0, changed state to up

- Please provide outputs of sh int, sh diag, and sh ver

- Install one card.  Configure the interface with an ip and run write mem.  Shut down the router and install the other card alone.  Does the router come back with the same interface name and IP?

- Please provide model numbers of both cards.


I'm guessing your tried "Interface FastEthernet1"

TodosNetwork Engineer

As mentioned above, You should have a Fastethernet port (on board) and an ethernet port (the WAN card).

You should be able to configure the Fastethernet 0 port with the "interface fastethernet 0" command and configure the (WAN) ethernet port with "interface ethernet 0".

If your WAN ethernet interface is not seen by your routerm check your IOS version, and router version. The link i gave above should give you info about that to. Maybe theres an IOS or hardware limitation issue.



I will check the IOS version, since according to the documentaiton this could stop the router from detecting the second card. Unfortunaltelly I won't have acces to that router before Wednesday. I'll post and update then...
TodosNetwork Engineer

ok Rajotico.
No comment has been added lately, so it's time to clean up this TA.
I will leave the following recommendation for this question in the Cleanup topic area:

Split: spinn420 {http:#9244641} & Todos {http:#9245800}

Please leave any comments here within the next four days.

Julian Crawford
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