I've got a G.703 (75 ohm BNC type) connected to a NM-1CE1U on a Cisco 3660 router. It's a 2mbps link. The controller keeps going down and them up again over and over. I contacted the telecom provider and they say everything is fine with the link itself. Here's a sample of the error message (I used 'term mon' for this):
Here is a log:
19:11:35 %CONTROLLER-5-UPDOWN: Controller E1 2/0, changed state to down
19:11:36 %CONTROLLER-5-UPDOWN: Controller E1 2/0, changed state to up
19:11:47 %CONTROLLER-5-UPDOWN: Controller E1 2/0, changed state to down
19:11:48 %CONTROLLER-5-UPDOWN: Controller E1 2/0, changed state to up
Notice that the controller only stays down only for a sec at a time.
Here is the running-config:
controller E1 2/0
channel-group 1 timeslots 1-31
ip address 172.16.100.73 255.255.255.252
ip access-group 100 in
no cdp enable
When the controller goes down the serial stays up. (Unless the controller is down for a long period of time.) But when this gets worse (the controller going down more frequently) I completely lose the WAN link.
What type of circuit is it exactly? You configured it to use all timeslots for a single serial link but with an E1, channels 0 and 15 are used for control signalling. Your setup includes channel 15 for datatransmission.
To use all available bandwidth you should configure chanel group 1 to contain channels 1-14 and 16-31. Syntax:
channel-group 1 timeslots 1-14, 16-31
This will result in a bandwidth of 1920 kb. If this is supposed to be an unstructured G703, you might have the wrong module or the wrong IOS version.
could it be you're confusing channelised E1 with ISDN PRI?
For ISDN PRI, slot 15 represents the D channel used for signalling, but I see no reason why you couldn't use 31 channels in a framed (fractional or channelised) E1 (where slot 0 is used for framing and there is no signalling).
All the framed E1's we use are 1984 kbps, so 31 x 64k.
I agree that if the line is unstructured G703 you need a different interface on the router, e.g. the VWIC-nMFT-G703 (n=1,2)
First off all, thank you for your time while trying to solve my problem
Well, Im sure the provider has installed a unstructured G703 link. In fact, I even know it is multiplexed and put on a SDH fiber ring to the destination. I have got other G703 with analogous configuration settings (also using the whole 31 time-slots) working perfectly well.
Another thing I have noticed, is that the controller doesnt just go down and up always. It only does this for a random period of time and them stops in an up status. Example: it works fine from 0:00 to 09:30, then from 9:30 until 12:30 it continuously changes state. After that it stays up for a long period of time again.
Youre probably wondering if the failures coincide with traffic peaks. Well, no it doesnt . Ive seen the link doing fine in busy hours.
I just have to be sure that there is no configuration problem with the router. By the way, the IOS version is 12.2(5a).
if you are really sure it is unstructured G.703 (also called unframed, clear channel or full 2Mb) then you have the wrong interface, the NM-nCE1 can only do structured E1 (also called framed E1, fractional E1, n x 64K, G.703 with G.704 structuring, or channelised E1 (when you have multiple links multiplexed on one E1)) or ISDN PRI, see http://www.cisco.com/warp/public/107/hw-e1.shtml#second
Anyway, assuming it is a framed E1, my next thought is that either the settings (also check crc4) do not match with those of the provider as Leo suggested, or that you may have a faulty network module. Any chance that you could try the same E1 on a different module, or this module on a different E1?
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