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Cisco 891 won't get an ip after a power outage

Posted on 2011-09-16
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Last Modified: 2012-08-13
Hello

I got a Cisco 891 wired to a DOCSIS 3.0 cable modem. Sometimes, we get power outage for several hours and the router and the modem are both shutdown. The problem is when they  both reload the router dont get an IP adress from the modem. I have to reset the interface each time... I am not always there to reset the interface and someone at the job have to connect to the router and reboot it. Is there a way to prevent this ?

Thanks
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Question by:metraon
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10 Comments
 
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Expert Comment

by:shbasm
ID: 36551204
in router under interface connected tp modem put ip address dhcp command
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Author Comment

by:metraon
ID: 36551288
The router have this command already.
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gsmartin earned 500 total points
ID: 36551380
I would recommend using a UPS with a line conditioner.  This will help to stablize power and keep the router from going down during brief power outages or brown outs.  What is the typical duration of the power outages?    
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Expert Comment

by:gsmartin
ID: 36551432
UPS: Depending on how many Watts the router and modem require, will depend on the UPS's Estimated Runtime (i.e. 50Watts with 1300Watt APC UPS - 2:34 min. Est. Runtime.).  The higher the wattage requirement the lower the Estimated Runtime.  FYI... You can also add an external battery pack to support an extended period on select models.
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Expert Comment

by:gsmartin
ID: 36551485
After a power outage, the modem would need to come up first an establish it's connection and then bring the router online.  If you don't have control over this process then it makes it difficult.
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Expert Comment

by:shbasm
ID: 36553823
use static ip address at router interface
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Expert Comment

by:Sanjeevloke
ID: 36554741
Do below test when u are there ...

1) Shut modem for sometime and do start it again and check if router gets IP
2) Shut router for sometime and keep modem ON and check again if routers gets IP.
3) When u face IP issue try to restart modem and check if it gets IP.

Can post IOS version many be a IOS bug is there ...
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Assisted Solution

by:gsmartin
gsmartin earned 500 total points
ID: 36556020
Static IP Adress would be the best solution to mitigate the issue.  However, DSL and Cable ISP providers typical implementation is DHCP.  

You may need to specifically request a set of Static IP addresses for your Internet connection, which is usually at an additional cost; depending on the ISP.  If for whatever reason, Static IP Addresses are not provided/supportted under the ISP's standard Internet services.  Then you may need to specifically request Business Class Internet services in order to get a set of Static IP addresses.  FYI...  Business Class is usually more expensive than standard DSL or Cable Internet services.  Cost and services will vary from provider to provider.  

Note there are other Internet connectivity options that are more stable, but also more costly (i.e. T1, Frame-Relay, MPLS, eWAN, etc....).  These options typically terminate directly on the router or another device like an external CSU/DSU, but I am sure you already know this.  Anyway, on a T1 circuit you can have it terminate at the router and then avoid any issues with secondary devices such as a modem or external CSU/DSU, as well as have static IPs.    
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Author Comment

by:metraon
ID: 36557799
Actually we have business class internet. I will request a static IP, i believe this will help...

I will also test :


1) Shut modem for sometime and do start it again and check if router gets IP
2) Shut router for sometime and keep modem ON and check again if routers gets IP.
3) When u face IP issue try to restart modem and check if it gets IP.

And post the iOS version soon

Many thanks
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Author Closing Comment

by:metraon
ID: 36574521
Obviously I need an UPS. I have requested an static IP address also.
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