Cisco T1 Internet Config

Discussion in 'Cisco' started by Alan Siu, May 2, 2007.

  1. Alan Siu

    Alan Siu Guest

    Hi,

    I am pretty new to cisco router config, but I have looked at various router
    configuration from our office existing router. I am just trying to
    understand the config done by our previous employee in our remote office, so
    please help me out. This is a T1 internet line by MCI and use unnumbered in
    their serial interface, here is what I don't understand as most of the line
    in our main office have ip on their serial interface.

    The line under Serial0/0
    encapsulation frame-relay IETF -- Do I need this line? This is not a frame
    relay but an internet line only.

    Also, the interface Serial0/0.1 part
    interface Serial0/0.1 point-to-point -- Do I need this 4 lines at all?
    bandwidth 1536
    ip unnumbered FastEthernet0/0
    frame-relay interface-dlci 500 IETF

    I just need a bare minimum for internet access only, and here is the
    complete config (removed lines with password and line)
    Please help, thank you so much.

    C2620-R2-R23#sh running-config
    Building configuration...

    Current configuration : 1528 bytes
    !
    ! No configuration change since last restart
    !
    version 12.3
    service timestamps debug datetime localtime
    service timestamps log datetime localtime
    service password-encryption
    !
    hostname C2620-R2-R23
    !
    boot-start-marker
    boot-end-marker
    !
    logging buffered 8196 debugging
    !
    memory-size iomem 15
    clock timezone PST -8
    clock summer-time PDT recurring
    no aaa new-model
    ip subnet-zero
    ip cef
    !
    ip audit po max-events 100
    !
    interface FastEthernet0/0
    description To Office Ethernet R23
    ip address 11.111.111.111 255.255.255.240
    duplex auto
    speed auto
    !
    interface Serial0/0
    bandwidth 1536
    no ip address
    encapsulation frame-relay IETF
    no fair-queue
    service-module t1 timeslots 1-24
    frame-relay lmi-type ansi
    !
    interface Serial0/0.1 point-to-point
    bandwidth 1536
    ip unnumbered FastEthernet0/0
    frame-relay interface-dlci 500 IETF
    !
    no ip http server
    no ip http secure-server
    ip classless
    ip route 0.0.0.0 0.0.0.0 Serial0/0.1
    !
    ntp clock-period 17180386
    ntp server 207.46.130.100 prefer
    !
    end


    --
    Thanks,
    Alan
     
    Alan Siu, May 2, 2007
    #1
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  2. Alan Siu

    Scooby Guest

    Alan,

    That is pretty close to bare minimum there. First, don't confuse your layer
    2 protocol with the services that are provided over the line. Meaning, just
    because this is internet, doesn't mean that the connection is not frame
    relay. If the line is functioning properly with this config, then it is
    certainly frame relay. That's like saying you don't have DSL/Cable, you
    have internet. Well, DSL/Cable just gets you to the service provider. In
    this case, frame relay is just getting you to the service provider.

    I personally would not have used a sub interface in this case as you only
    have one pvc and frame relay would most likely have just auto discovered it
    through lmi - no other config for this would have been needed. Except the
    ip unnumbered command would have moved to the serial interface. But, it is
    not a bad config as is.

    So, if it ain't broke....

    But, you may want to consider hardening this a little bit. Check out the
    SDM utility - free download from Cisco. Great place to get started on this
    stuff.

    Jim



    "Alan Siu" <> wrote in message
    news:f1a57n$cl1$...
    > Hi,
    >
    > I am pretty new to cisco router config, but I have looked at various
    > router configuration from our office existing router. I am just trying to
    > understand the config done by our previous employee in our remote office,
    > so please help me out. This is a T1 internet line by MCI and use
    > unnumbered in their serial interface, here is what I don't understand as
    > most of the line in our main office have ip on their serial interface.
    >
    > The line under Serial0/0
    > encapsulation frame-relay IETF -- Do I need this line? This is not a frame
    > relay but an internet line only.
    >
    > Also, the interface Serial0/0.1 part
    > interface Serial0/0.1 point-to-point -- Do I need this 4 lines at all?
    > bandwidth 1536
    > ip unnumbered FastEthernet0/0
    > frame-relay interface-dlci 500 IETF
    >
    > I just need a bare minimum for internet access only, and here is the
    > complete config (removed lines with password and line)
    > Please help, thank you so much.
    >
    > C2620-R2-R23#sh running-config
    > Building configuration...
    >
    > Current configuration : 1528 bytes
    > !
    > ! No configuration change since last restart
    > !
    > version 12.3
    > service timestamps debug datetime localtime
    > service timestamps log datetime localtime
    > service password-encryption
    > !
    > hostname C2620-R2-R23
    > !
    > boot-start-marker
    > boot-end-marker
    > !
    > logging buffered 8196 debugging
    > !
    > memory-size iomem 15
    > clock timezone PST -8
    > clock summer-time PDT recurring
    > no aaa new-model
    > ip subnet-zero
    > ip cef
    > !
    > ip audit po max-events 100
    > !
    > interface FastEthernet0/0
    > description To Office Ethernet R23
    > ip address 11.111.111.111 255.255.255.240
    > duplex auto
    > speed auto
    > !
    > interface Serial0/0
    > bandwidth 1536
    > no ip address
    > encapsulation frame-relay IETF
    > no fair-queue
    > service-module t1 timeslots 1-24
    > frame-relay lmi-type ansi
    > !
    > interface Serial0/0.1 point-to-point
    > bandwidth 1536
    > ip unnumbered FastEthernet0/0
    > frame-relay interface-dlci 500 IETF
    > !
    > no ip http server
    > no ip http secure-server
    > ip classless
    > ip route 0.0.0.0 0.0.0.0 Serial0/0.1
    > !
    > ntp clock-period 17180386
    > ntp server 207.46.130.100 prefer
    > !
    > end
    >
    >
    > --
    > Thanks,
    > Alan
    >
     
    Scooby, May 2, 2007
    #2
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  3. "Alan Siu" <> writes:
    >The line under Serial0/0
    >encapsulation frame-relay IETF -- Do I need this line? This is not a frame
    >relay but an internet line only.


    MCI uses frame-relay layer-2 encapsulation for most of their delivery
    for their own management policies. Doesn't mean its a frame-relay network.
    You do need this line, as you have to match what MCI is doing. If MCI
    requires frame-relay layer-2 encapsulation, you have to match what
    they want.

    >Also, the interface Serial0/0.1 part
    >interface Serial0/0.1 point-to-point -- Do I need this 4 lines at all?
    > bandwidth 1536
    > ip unnumbered FastEthernet0/0
    > frame-relay interface-dlci 500 IETF


    Its best to put frame-relay entries in a sub-interface, and you do
    need the DLCI definition in order to talk to MCI across the link.

    Technically, you aren't doing anything that references the bandwidth
    line, but why remove it? You may do something in the future that does.

    You appear to be running unnumbered across the serial link, and thats
    what 'ip unnumbered' does. You do need it, its required for your setup
    again with MCI.

    >I just need a bare minimum for internet access only, and here is the
    >complete config (removed lines with password and line)


    This config is pretty bare-bones basic. There isn't much you can
    remove and still have it function to match what MCI is doing.

    Why are you considering removing anything?

    There isn't anything you could make "simpler" about this config.
     
    Doug McIntyre, May 2, 2007
    #3
  4. Alan Siu

    Alan Siu Guest

    Yes correct, that's MCI line. Does it mean the config may vary between
    different ISP? When I look at the config in the remote office compared to
    the one I have in my local office, it just look a lot more complicated than
    the config on my T1 router. Compared to the T1 I have with Verizon with an
    IP in the serial interface, it looks a lot simpler.

    interface Serial0

    ip address 111.111.111.111 255.255.255.252

    no ip redirects

    no fair-queue

    !

    interface FastEthernet0

    ip address 222.222.222.222 255.255.255.248

    no ip redirects

    speed auto

    full-duplex

    !

    ip classless

    ip route 0.0.0.0 0.0.0.0 121.121.121.121

    no ip http server


    Last question, does the config varies between 1700 or 2600 series router?
    Why there is a sub-interface Serial 0/0 and 0/0.1 in 2600 series but in 1700
    series, you only have interface Serial 0 or 1?

    Thanks for all the people who answered.


    --
    Thanks,
    Alan
    "Doug McIntyre" <> wrote in message
    news:4638b682$0$36710$...
    > "Alan Siu" <> writes:
    >>The line under Serial0/0
    >>encapsulation frame-relay IETF -- Do I need this line? This is not a frame
    >>relay but an internet line only.

    >
    > MCI uses frame-relay layer-2 encapsulation for most of their delivery
    > for their own management policies. Doesn't mean its a frame-relay network.
    > You do need this line, as you have to match what MCI is doing. If MCI
    > requires frame-relay layer-2 encapsulation, you have to match what
    > they want.
    >
    >>Also, the interface Serial0/0.1 part
    >>interface Serial0/0.1 point-to-point -- Do I need this 4 lines at all?
    >> bandwidth 1536
    >> ip unnumbered FastEthernet0/0
    >> frame-relay interface-dlci 500 IETF

    >
    > Its best to put frame-relay entries in a sub-interface, and you do
    > need the DLCI definition in order to talk to MCI across the link.
    >
    > Technically, you aren't doing anything that references the bandwidth
    > line, but why remove it? You may do something in the future that does.
    >
    > You appear to be running unnumbered across the serial link, and thats
    > what 'ip unnumbered' does. You do need it, its required for your setup
    > again with MCI.
    >
    >>I just need a bare minimum for internet access only, and here is the
    >>complete config (removed lines with password and line)

    >
    > This config is pretty bare-bones basic. There isn't much you can
    > remove and still have it function to match what MCI is doing.
    >
    > Why are you considering removing anything?
    >
    > There isn't anything you could make "simpler" about this config.
    >
    >
    >
     
    Alan Siu, May 2, 2007
    #4
  5. On Wed, 02 May 2007 17:40:21 -0400, Alan Siu wrote:

    > Yes correct, that's MCI line. Does it mean the config may vary between
    > different ISP?


    Yes.

    > When I look at the config in the remote office compared to
    > the one I have in my local office, it just look a lot more complicated than
    > the config on my T1 router. Compared to the T1 I have with Verizon with an
    > IP in the serial interface, it looks a lot simpler.
    >
    > interface Serial0
    > ip address 111.111.111.111 255.255.255.252
    > no ip redirects
    > no fair-queue


    Verizon are using HDLC encapsulation, which is the default on Cisco
    routers, what you get if you don't do anything else, so it does look
    simpler. I guess HDLC is also a simpler protocol then Frame Relay.

    >
    > Last question, does the config varies between 1700 or 2600 series router?


    Yes and No, more no than yes. The same technology, a Frame Relay
    interface for instance, is the same on both routers.

    > Why there is a sub-interface Serial 0/0 and 0/0.1 in 2600 series but in
    > 1700 series, you only have interface Serial 0 or 1?


    Interface numbering differs across platforms, depending on the number
    and type of available slots on the router. Subinterfaces are used with
    frame-relay encapsulation but not with HDLC.

    --
    Rgds,
    Martin
     
    Martin Gallagher, May 4, 2007
    #5
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