A couple questions

royalroyal Posts: 3,353Member
I don't have much Cisco knowledge, although I would like to, but no time. I do have a couple questions that I have always wondered, but never bothered to ask till now.

1. WAN Redundancy - So let's say I have a T1 connection to my business. I don't want a single point of failure so I plan on purchasing another T1 from another company. How exactly do companies implement WAN redundancy with 2 different network connections. Do most Cisco routers provide a mechanism to allow 2 different modules to provide an interface to 2 different T1 connections? I'm assuming so, and if that's the case, can you configure these 2 WAN links to both be active at the same time providing twice the bandwidth? I'm assuming you can also configure it so one is in Active/Passive mode?

2. I also know that Cisco routers have modules that provide T1 interface connectivity. Is the CSU/DSU built into the router itself or is it the purchasble module that provides the T1 interface that has the CSU/DSU?

3. When a T1 is being connected to the module in a router, I do know that there are 12 channels in a T1. After the T1 line is plugged into the router's module, how exactly do you split the channels into voice/data. I know the router would be connected to a switch which would provide the cabling for the data, but how would a a cable from the switch know that this cable is using lets say 4 out of the 12 T1 channels?

Thanks in advance for the answers.
“For success, attitude is equally as important as ability.” - Harry F. Banks


  • Paul#4Paul#4 Posts: 57Inactive Imported Users ■■□□□□□□□□
    1. Most people go with Frame-Relay which will provide service over a T1 infrastructure(leased line). With Frame-Relay you can have multiple VC's(virtual circuits) which allow for as much bandwith as you need. You can configure these VC's for redundancy or they can be used to connect with different remote sites. You don't need seperate modules, you can have multiple VC's on one interface. I can't remember how many VC's per interface but you can support a lot of traffic on one interface.

    2. You can have a CSU/DSU card for a router or an external CSU/DSU. It all depends on what you need and what kind of router you purchase.

    3. T1 has 23 channels for Data and 1 Channel for signaling, which is 24 channels total.
    I don't know about traffic shaping with voice/data but it all works out really good.

    Cisco is really fun stuff. If you ever have time go for the CCNA and see if you like it.
    I want to get my MCSE eventually. I am so behind on MS technologies I would be completely lost trying to configure MS Servers nowadays(unless I used my NT4.0 knowledge)...

    Gimme gimme gimme
  • Paul BozPaul Boz Posts: 2,621Member ■■■■■■■■□□
    Multihoming is what you're talking about.
    CCNA Security | GSEC |GCFW | GCIH | GCIA
    [email protected]
    Blog: http://www.infosiege.net/
  • rossonieri#1rossonieri#1 Posts: 800Member
    hi royal,

    answer # 1 :
    yes, the 2 connection can be active and passive/backup ( 1 up and 1 standby), and can be active-active (multi-gateway/multihoming).

    answer # 2 :
    there 2 kinds of CSU/DSU - 1 built-in, 1 external.

    answer # 3 :
    channelized/fractional T1 consist of several B channels, we split it when configuring the serial interface.


    the More I know, that is more and More I dont know.
  • royalroyal Posts: 3,353Member
    I've always been interested in learning more about Cisco. Is this kind of stuff explained in the CCNA or something like the CCDA? I think I will eventually go for my CCNA but still have a bunch of stuff to do before I can even think about doing my CCNA.
    “For success, attitude is equally as important as ability.” - Harry F. Banks
  • Paul BozPaul Boz Posts: 2,621Member ■■■■■■■■□□
    Yes, understanding WAN technologies is on the core curriculum for the CCNA and CCNP.
    CCNA Security | GSEC |GCFW | GCIH | GCIA
    [email protected]
    Blog: http://www.infosiege.net/
  • CucumberCucumber Posts: 192Member
    Ok, here are my answers, Im sure someone will correct me if Im wrong. icon_wink.gif

    1. If you are hosting internet servers on your network, using two ISPs gets tricky at the moment of assigning IP addresses for your servers.
    If you are not hosting servers, its easy, just use two floating default routes (this option will not give you load balancing)
    If you want to load balance traffic to/from two different ISPs, then you would need BGP, a bit too much for small companies IMO.

    2. The provider usually gives you the CSU/DSU. Getting an external CSU/DSU on your own may be expensive FWIK, also getting a T1 card with an integrated CSU/DSU is expensive too.

    3. What I have seen in those cases is having an external demux box, that will get connected the T1 as input and will dechanelize the T1 into two output links (two coax cables), one coax cable get connected to the router's T1 interface and the other to the PBX. I seen this 7 years ago so I dont know if its still the best solution.
                    /(Data channels)
                    \(Voice Channels)
    I hate pandas
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