connecting a modem to the AUX port

Answered Question
Jun 11th, 2009
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i'm considering connecting a modem to the 1841 RTRs at our two remote sites.

i thought i'd use the AUX port to do this. but i also want to create an ACL that will automatically send the traffic down the AUX if the main connection goes south.

I'm sure someone has done this before.

Any thoughts?

Thanks, Gary

Correct Answer by gooditadmin about 7 years 8 months ago

(a comment on the usefulness of this type of connection)


I have a remote site to which we have T1 service, but no DSL or Cable internet service is available (for VPN). If the T1 goes down, much of the business there can still be done over telnet. Also, if I had that connection I could more accurately diagnose the outage (my equipment vs. telco).



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Paolo Bevilacqua Thu, 06/11/2009 - 09:49
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You can do that with a floating static route for example.


Note that dial-up modems are so slow, that make a backup based on that practically useless for today networking.

garyrivers Thu, 06/11/2009 - 10:37
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true, they are slow but we are trying to do this on the low-low.

is there another way of creating a backup as like a modem?

do you have any examples of floating static routes?


Thanks, Gary

Paolo Bevilacqua Thu, 06/11/2009 - 10:44
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Search "async dialer PPP" on CCO.

It is not a very easy configuration and may not be worth the effort considering the results.

Paolo Bevilacqua Thu, 06/11/2009 - 20:15
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You're welcome, please remember to rate useful posts with the scrollbox below.

hobbe Tue, 07/14/2009 - 06:18
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Depending on the router you actually have modemcards to install.

Same if you have ISDN. xDSL and so on.


Example for the 1841. WIC-1AM or WIC-2AM and then you have WIC-2AM-V2 and so on.



I would like to point out the same as the previous answerer, modem, to day, is in all practicallity a no go situation.

however if you just need to test then i think you atleast can come close to emulating one if you do a QOS, that should bring you down to aprox 64K. not realy there but close enough to make it unbearable to work with. (unless we talk 1 user and only keyboard, mouse and screen traffic).


garyrivers Tue, 07/14/2009 - 06:29
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If the circuit goes down, all we will want is to get to the RTR and 2/3 other PCs.

so, hopefully, speed will not be too big of an issue.

i was able to get routing figured out by using the "sla monitor" command.

hobbe Tue, 07/14/2009 - 06:37
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if all you need is to get to the router and some other PC's then I would suggest that you use VPN or set a specific link to a normally unused network that you can connect from so that the links does not get so bogged down with traffic that it is useless.


hth

garyrivers Tue, 07/14/2009 - 07:11
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you're right, if we don't filter the traffic the dial up will become unuseable.

so that's why we created an ACL to block all traffic except for 4 boxes.

hobbe Wed, 07/15/2009 - 04:10
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How are you going to apply that filter if the line is oversubscribed already and you can not reach the router due to congestions ?


if I do not understand you wrong, you would come over the modem link and that would only happen if there is a error that disables the normal route, so timewise you would have error, change path, and then you would try to log in and add an access-list ?


or am I missing something here ?

scripting ?



garyrivers Wed, 07/15/2009 - 05:44
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if the main line goes down the only IPs that going to traverse the RTR are going to be highly mission-critical, such as the RTR, transmitter remote control, etc. a total of 4 IPs.

in order to filter the rest of the traffic we are placing an ACL on the Dialer interface blocking the rest of the traffic.

Gary

Correct Answer
gooditadmin Mon, 07/20/2009 - 12:44
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(a comment on the usefulness of this type of connection)


I have a remote site to which we have T1 service, but no DSL or Cable internet service is available (for VPN). If the T1 goes down, much of the business there can still be done over telnet. Also, if I had that connection I could more accurately diagnose the outage (my equipment vs. telco).



garyrivers Mon, 07/20/2009 - 12:59
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the dialup connections for the 3 remote sites are on line. and the line was alittle slow during testing but it wasn't unuseable.

but i can see the point of not doing production over a modem connection.

Gary

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