Help configuring Point-To-Point T1

Discussion in 'Cisco' started by jlamanna@gmail.com, Sep 19, 2007.

  1. Guest

    Hi,
    I have a point-to-point T1 (private line) between 2 offices.
    I have Cisco 3560 switches at both locations.
    At one location I have an external CSU/DSU, and at the other location
    I have a Cisco 2851 with a CSU/DSU port free on the WIC card.

    My intention was to trunk the 2 Cisco 3560s together over the T1,
    however I'm confused as to how to configure the serial interface on
    the 2851 to pass-through to the 3560.

    Thanks.
     
    , Sep 19, 2007
    #1
    1. Advertising

  2. On Sep 18, 9:13 pm, "" <> wrote:
    > Hi,
    > I have a point-to-point T1 (private line) between 2 offices.
    > I have Cisco 3560 switches at both locations.
    > At one location I have an external CSU/DSU, and at the other location
    > I have a Cisco 2851 with a CSU/DSU port free on the WIC card.
    >
    > My intention was to trunk the 2 Cisco 3560s together over the T1,
    > however I'm confused as to how to configure the serial interface on
    > the 2851 to pass-through to the 3560.
    >
    > Thanks.


    I'm kind of confused on exactly what your situation is.

    How are you connecting the 3560 to the external CSU/DSU? Do you have
    a router there too?

    Are you wanting to create a VLAN trunk between the two switches? So
    that you could have a VLAN that spans across both offices? If so,
    then, I don't think you can really do that. A 802.1q VLAN trunk uses
    taking in the Ethernet header to identify which VLAN a packet belongs
    on. The Ethernet headers would be dropped before it goes onto the T1
    serial link, because the T1 line does not use Ethernet as a L2
    protocol - it uses PPP/HDLC/etc. You also wouldn't really want to
    have the VLAN going over the WAN because all of the broadcasts on that
    network would be needlessly forwarded over the WAN wasting bandwidth
    on the relatively low-bandwidth WAN connection.

    You could certainly have VLAN's set up on both sides of the WAN, and
    use the routers to route between them, but each VLAN would only exist
    on one side of the WAN.

    Sorry if I misunderstood your question.
     
    Oliver Garraux, Sep 19, 2007
    #2
    1. Advertising

  3. Guest

    On Sep 18, 8:28 pm, Oliver Garraux <> wrote:
    > On Sep 18, 9:13 pm, "" <> wrote:
    >
    > > Hi,
    > > I have a point-to-point T1 (private line) between 2 offices.
    > > I have Cisco 3560 switches at both locations.
    > > At one location I have an external CSU/DSU, and at the other location
    > > I have a Cisco 2851 with a CSU/DSU port free on the WIC card.

    >
    > > My intention was to trunk the 2 Cisco 3560s together over the T1,
    > > however I'm confused as to how to configure the serial interface on
    > > the 2851 to pass-through to the 3560.

    >
    > > Thanks.

    >
    > I'm kind of confused on exactly what your situation is.
    >
    > How are you connecting the 3560 to the external CSU/DSU? Do you have
    > a router there too?
    >
    > Are you wanting to create a VLAN trunk between the two switches? So
    > that you could have a VLAN that spans across both offices? If so,
    > then, I don't think you can really do that. A 802.1q VLAN trunk uses
    > taking in the Ethernet header to identify which VLAN a packet belongs
    > on. The Ethernet headers would be dropped before it goes onto the T1
    > serial link, because the T1 line does not use Ethernet as a L2
    > protocol - it uses PPP/HDLC/etc. You also wouldn't really want to
    > have the VLAN going over the WAN because all of the broadcasts on that
    > network would be needlessly forwarded over the WAN wasting bandwidth
    > on the relatively low-bandwidth WAN connection.
    >
    > You could certainly have VLAN's set up on both sides of the WAN, and
    > use the routers to route between them, but each VLAN would only exist
    > on one side of the WAN.
    >
    > Sorry if I misunderstood your question.


    Ok, here's my situation (with hopefully gorey enough details).
    Office 1 (current) :
    1700 series router (1 WIC port) w/ Internet T1
    Bunch of servers (staying put)
    VOIP PBX (staying put) w/ Voice T1
    Currently unused Adtran CSU/DSU
    3560 Switch
    A couple PCs

    Office 2 (new):
    2851 Router (2 VWIC ports) w/ Internet T1
    3560 Switch
    Bunch of PCs that need server access to the servers at Office 1
    Phones that need access to the VOIP PBX at Office 1

    Here's what I was hoping to do:

    VLAN for servers
    VLAN for PCs at Office 1
    VLAN for PCs at Office 2
    VLAN for VOIP stuff

    I was hoping to use the 3560 to statically route between the VLANs at
    the offices by sending the traffic to the specific switchport.
    So as an example the 3560 in Office 2 would have the server VLAN setup
    and then have a route to the P-T-P switchport, etc..
    Apparently this may not be possible.

    What additional hw/reorganization would I need to make it possible?

    Thanks.
     
    , Sep 19, 2007
    #3
  4. Guest

    On Sep 18, 9:32 pm, "" <> wrote:
    > On Sep 18, 8:28 pm, Oliver Garraux <> wrote:
    >
    >
    >
    > > On Sep 18, 9:13 pm, "" <> wrote:

    >
    > > > Hi,
    > > > I have a point-to-point T1 (private line) between 2 offices.
    > > > I have Cisco 3560 switches at both locations.
    > > > At one location I have an external CSU/DSU, and at the other location
    > > > I have a Cisco 2851 with a CSU/DSU port free on the WIC card.

    >
    > > > My intention was to trunk the 2 Cisco 3560s together over the T1,
    > > > however I'm confused as to how to configure the serial interface on
    > > > the 2851 to pass-through to the 3560.

    >
    > > > Thanks.

    >
    > > I'm kind of confused on exactly what your situation is.

    >
    > > How are you connecting the 3560 to the external CSU/DSU? Do you have
    > > a router there too?

    >
    > > Are you wanting to create a VLAN trunk between the two switches? So
    > > that you could have a VLAN that spans across both offices? If so,
    > > then, I don't think you can really do that. A 802.1q VLAN trunk uses
    > > taking in the Ethernet header to identify which VLAN a packet belongs
    > > on. The Ethernet headers would be dropped before it goes onto the T1
    > > serial link, because the T1 line does not use Ethernet as a L2
    > > protocol - it uses PPP/HDLC/etc. You also wouldn't really want to
    > > have the VLAN going over the WAN because all of the broadcasts on that
    > > network would be needlessly forwarded over the WAN wasting bandwidth
    > > on the relatively low-bandwidth WAN connection.

    >
    > > You could certainly have VLAN's set up on both sides of the WAN, and
    > > use the routers to route between them, but each VLAN would only exist
    > > on one side of the WAN.

    >
    > > Sorry if I misunderstood your question.

    >
    > Ok, here's my situation (with hopefully gorey enough details).
    > Office 1 (current) :
    > 1700 series router (1 WIC port) w/ Internet T1
    > Bunch of servers (staying put)
    > VOIP PBX (staying put) w/ Voice T1
    > Currently unused Adtran CSU/DSU
    > 3560 Switch
    > A couple PCs
    >
    > Office 2 (new):
    > 2851 Router (2 VWIC ports) w/ Internet T1
    > 3560 Switch
    > Bunch of PCs that need server access to the servers at Office 1
    > Phones that need access to the VOIP PBX at Office 1
    >
    > Here's what I was hoping to do:
    >
    > VLAN for servers
    > VLAN for PCs at Office 1
    > VLAN for PCs at Office 2
    > VLAN for VOIP stuff
    >
    > I was hoping to use the 3560 to statically route between the VLANs at
    > the offices by sending the traffic to the specific switchport.
    > So as an example the 3560 in Office 2 would have the server VLAN setup
    > and then have a route to the P-T-P switchport, etc..
    > Apparently this may not be possible.
    >
    > What additional hw/reorganization would I need to make it possible?
    >
    > Thanks.


    Also, I emailed Cisco and they said I could use Transparent Bridging
    to connect the 2 networks over the PPP link.
     
    , Sep 19, 2007
    #4
  5. On Sep 19, 12:32 am, "" <> wrote:
    > On Sep 18, 8:28 pm, Oliver Garraux <> wrote:
    >
    >
    >
    > > On Sep 18, 9:13 pm, "" <> wrote:

    >
    > > > Hi,
    > > > I have a point-to-point T1 (private line) between 2 offices.
    > > > I have Cisco 3560 switches at both locations.
    > > > At one location I have an external CSU/DSU, and at the other location
    > > > I have a Cisco 2851 with a CSU/DSU port free on the WIC card.

    >
    > > > My intention was to trunk the 2 Cisco 3560s together over the T1,
    > > > however I'm confused as to how to configure the serial interface on
    > > > the 2851 to pass-through to the 3560.

    >
    > > > Thanks.

    >
    > > I'm kind of confused on exactly what your situation is.

    >
    > > How are you connecting the 3560 to the external CSU/DSU? Do you have
    > > a router there too?

    >
    > > Are you wanting to create a VLAN trunk between the two switches? So
    > > that you could have a VLAN that spans across both offices? If so,
    > > then, I don't think you can really do that. A 802.1q VLAN trunk uses
    > > taking in the Ethernet header to identify which VLAN a packet belongs
    > > on. The Ethernet headers would be dropped before it goes onto the T1
    > > serial link, because the T1 line does not use Ethernet as a L2
    > > protocol - it uses PPP/HDLC/etc. You also wouldn't really want to
    > > have the VLAN going over the WAN because all of the broadcasts on that
    > > network would be needlessly forwarded over the WAN wasting bandwidth
    > > on the relatively low-bandwidth WAN connection.

    >
    > > You could certainly have VLAN's set up on both sides of the WAN, and
    > > use the routers to route between them, but each VLAN would only exist
    > > on one side of the WAN.

    >
    > > Sorry if I misunderstood your question.

    >
    > Ok, here's my situation (with hopefully gorey enough details).
    > Office 1 (current) :
    > 1700 series router (1 WIC port) w/ Internet T1
    > Bunch of servers (staying put)
    > VOIP PBX (staying put) w/ Voice T1
    > Currently unused Adtran CSU/DSU
    > 3560 Switch
    > A couple PCs
    >
    > Office 2 (new):
    > 2851 Router (2 VWIC ports) w/ Internet T1
    > 3560 Switch
    > Bunch of PCs that need server access to the servers at Office 1
    > Phones that need access to the VOIP PBX at Office 1
    >
    > Here's what I was hoping to do:
    >
    > VLAN for servers
    > VLAN for PCs at Office 1
    > VLAN for PCs at Office 2
    > VLAN for VOIP stuff
    >
    > I was hoping to use the 3560 to statically route between the VLANs at
    > the offices by sending the traffic to the specific switchport.
    > So as an example the 3560 in Office 2 would have the server VLAN setup
    > and then have a route to the P-T-P switchport, etc..
    > Apparently this may not be possible.
    >
    > What additional hw/reorganization would I need to make it possible?
    >
    > Thanks.


    OK, I think I understand what you're wanting to do now. If your
    switches support a dynamic routing protocol (even RIP should probably
    work OK in this case), it might make it a bit easier to configure
    because you wouldn't have to worry about tons of static routes.

    The only places you have to worry about the VLAN's is on the 3560's.
    You only have to set up the local VLAN's on the local switch. So, the
    3560 @ office 1 just needs Office 1's VLAN's added to its VLAN
    databaset. And the same for office 2.

    You just have to configure the 3560's to route between those local
    VLAN's, and to have the attached router as its default gateway. Then,
    you have to set up static routes on the routers. So, office 1's
    router would have static routes to all of the office 1 VLAN's with the
    3560's IP as the next hop. And office 2's router would have static
    routes to all of the office 2 VLAN's with the 3560 at office 2 as the
    next hop. Then on your routers you should set up static routes to the
    other office's VLAN's. You would add static routes on office 1's
    router to all of the VLAN's at office 2 with the office 2 router as
    the next hop and vice versa.

    You should try to use a dynamic routing protocol if you can, it'll
    make it easier to configure, and easier to change your network
    structure later on. I think the 3560's should support RIP even if
    they have SMI, and RIP should work OK in this case. If you are using
    RIP, then you should just add each of the local VLAN's networks to RIP
    on each of the 3560's. And just add the networks (ie, the serial link
    and link to the 3560) that are directly connected to the routers to
    RIP on the routers at each office. And make sure RIP is enabled for
    all of the appropriate interfaces. If you have EMI on your 3560's,
    then I think you are even be able to use EIGRP or OSPF or something
    much more modern than RIP.

    Hope that helps a little,

    Oliver
     
    Oliver Garraux, Sep 19, 2007
    #5
  6. Guest

    On Sep 18, 11:18 pm, Oliver Garraux <> wrote:
    > On Sep 19, 12:32 am, "" <> wrote:
    >
    >
    >
    > > On Sep 18, 8:28 pm, Oliver Garraux <> wrote:

    >
    > > > On Sep 18, 9:13 pm, "" <> wrote:

    >
    > > > > Hi,
    > > > > I have a point-to-point T1 (private line) between 2 offices.
    > > > > I have Cisco 3560 switches at both locations.
    > > > > At one location I have an external CSU/DSU, and at the other location
    > > > > I have a Cisco 2851 with a CSU/DSU port free on the WIC card.

    >
    > > > > My intention was to trunk the 2 Cisco 3560s together over the T1,
    > > > > however I'm confused as to how to configure the serial interface on
    > > > > the 2851 to pass-through to the 3560.

    >
    > > > > Thanks.

    >
    > > > I'm kind of confused on exactly what your situation is.

    >
    > > > How are you connecting the 3560 to the external CSU/DSU? Do you have
    > > > a router there too?

    >
    > > > Are you wanting to create a VLAN trunk between the two switches? So
    > > > that you could have a VLAN that spans across both offices? If so,
    > > > then, I don't think you can really do that. A 802.1q VLAN trunk uses
    > > > taking in the Ethernet header to identify which VLAN a packet belongs
    > > > on. The Ethernet headers would be dropped before it goes onto the T1
    > > > serial link, because the T1 line does not use Ethernet as a L2
    > > > protocol - it uses PPP/HDLC/etc. You also wouldn't really want to
    > > > have the VLAN going over the WAN because all of the broadcasts on that
    > > > network would be needlessly forwarded over the WAN wasting bandwidth
    > > > on the relatively low-bandwidth WAN connection.

    >
    > > > You could certainly have VLAN's set up on both sides of the WAN, and
    > > > use the routers to route between them, but each VLAN would only exist
    > > > on one side of the WAN.

    >
    > > > Sorry if I misunderstood your question.

    >
    > > Ok, here's my situation (with hopefully gorey enough details).
    > > Office 1 (current) :
    > > 1700 series router (1 WIC port) w/ Internet T1
    > > Bunch of servers (staying put)
    > > VOIP PBX (staying put) w/ Voice T1
    > > Currently unused Adtran CSU/DSU
    > > 3560 Switch
    > > A couple PCs

    >
    > > Office 2 (new):
    > > 2851 Router (2 VWIC ports) w/ Internet T1
    > > 3560 Switch
    > > Bunch of PCs that need server access to the servers at Office 1
    > > Phones that need access to the VOIP PBX at Office 1

    >
    > > Here's what I was hoping to do:

    >
    > > VLAN for servers
    > > VLAN for PCs at Office 1
    > > VLAN for PCs at Office 2
    > > VLAN for VOIP stuff

    >
    > > I was hoping to use the 3560 to statically route between the VLANs at
    > > the offices by sending the traffic to the specific switchport.
    > > So as an example the 3560 in Office 2 would have the server VLAN setup
    > > and then have a route to the P-T-P switchport, etc..
    > > Apparently this may not be possible.

    >
    > > What additional hw/reorganization would I need to make it possible?

    >
    > > Thanks.

    >
    > OK, I think I understand what you're wanting to do now. If your
    > switches support a dynamic routing protocol (even RIP should probably
    > work OK in this case), it might make it a bit easier to configure
    > because you wouldn't have to worry about tons of static routes.
    >
    > The only places you have to worry about the VLAN's is on the 3560's.
    > You only have to set up the local VLAN's on the local switch. So, the
    > 3560 @ office 1 just needs Office 1's VLAN's added to its VLAN
    > databaset. And the same for office 2.
    >
    > You just have to configure the 3560's to route between those local
    > VLAN's, and to have the attached router as its default gateway. Then,
    > you have to set up static routes on the routers. So, office 1's
    > router would have static routes to all of the office 1 VLAN's with the
    > 3560's IP as the next hop. And office 2's router would have static
    > routes to all of the office 2 VLAN's with the 3560 at office 2 as the
    > next hop. Then on your routers you should set up static routes to the
    > other office's VLAN's. You would add static routes on office 1's
    > router to all of the VLAN's at office 2 with the office 2 router as
    > the next hop and vice versa.
    >
    > You should try to use a dynamic routing protocol if you can, it'll
    > make it easier to configure, and easier to change your network
    > structure later on. I think the 3560's should support RIP even if
    > they have SMI, and RIP should work OK in this case. If you are using
    > RIP, then you should just add each of the local VLAN's networks to RIP
    > on each of the 3560's. And just add the networks (ie, the serial link
    > and link to the 3560) that are directly connected to the routers to
    > RIP on the routers at each office. And make sure RIP is enabled for
    > all of the appropriate interfaces. If you have EMI on your 3560's,
    > then I think you are even be able to use EIGRP or OSPF or something
    > much more modern than RIP.
    >
    > Hope that helps a little,
    >
    > Oliver


    Thanks Oliver.
    The only caveat is that I don't have another router @ Office 1 - right
    now it's just a 1720 with a WIC card for the existing T1.
    Cisco seems to insist that the following configuration works with
    bridging:

    3560 -> 2851 -> p-t-p T1 -> Adtran CSU/DSU -> 3560.
    Have you ever heard of that?

    -- James
     
    , Sep 19, 2007
    #6
  7. Guest

    The adtran just gives you an ethernet hand-off. We had one for a temp
    solution... It worked well.

    On Sep 19, 2:08 pm, "" <> wrote:
    > On Sep 18, 11:18 pm, Oliver Garraux <> wrote:
    >
    >
    >
    > > On Sep 19, 12:32 am, "" <> wrote:

    >
    > > > On Sep 18, 8:28 pm, Oliver Garraux <> wrote:

    >
    > > > > On Sep 18, 9:13 pm, "" <> wrote:

    >
    > > > > > Hi,
    > > > > > I have a point-to-point T1 (private line) between 2 offices.
    > > > > > I have Cisco 3560 switches at both locations.
    > > > > > At one location I have an external CSU/DSU, and at the other location
    > > > > > I have a Cisco 2851 with a CSU/DSU port free on the WIC card.

    >
    > > > > > My intention was to trunk the 2 Cisco 3560s together over the T1,
    > > > > > however I'm confused as to how to configure the serial interface on
    > > > > > the 2851 to pass-through to the 3560.

    >
    > > > > > Thanks.

    >
    > > > > I'm kind of confused on exactly what your situation is.

    >
    > > > > How are you connecting the 3560 to the external CSU/DSU? Do you have
    > > > > a router there too?

    >
    > > > > Are you wanting to create a VLAN trunk between the two switches? So
    > > > > that you could have a VLAN that spans across both offices? If so,
    > > > > then, I don't think you can really do that. A 802.1q VLAN trunk uses
    > > > > taking in the Ethernet header to identify which VLAN a packet belongs
    > > > > on. The Ethernet headers would be dropped before it goes onto the T1
    > > > > serial link, because the T1 line does not use Ethernet as a L2
    > > > > protocol - it uses PPP/HDLC/etc. You also wouldn't really want to
    > > > > have the VLAN going over the WAN because all of the broadcasts on that
    > > > > network would be needlessly forwarded over the WAN wasting bandwidth
    > > > > on the relatively low-bandwidth WAN connection.

    >
    > > > > You could certainly have VLAN's set up on both sides of the WAN, and
    > > > > use the routers to route between them, but each VLAN would only exist
    > > > > on one side of the WAN.

    >
    > > > > Sorry if I misunderstood your question.

    >
    > > > Ok, here's my situation (with hopefully gorey enough details).
    > > > Office 1 (current) :
    > > > 1700 series router (1 WIC port) w/ Internet T1
    > > > Bunch of servers (staying put)
    > > > VOIP PBX (staying put) w/ Voice T1
    > > > Currently unused Adtran CSU/DSU
    > > > 3560 Switch
    > > > A couple PCs

    >
    > > > Office 2 (new):
    > > > 2851 Router (2 VWIC ports) w/ Internet T1
    > > > 3560 Switch
    > > > Bunch of PCs that need server access to the servers at Office 1
    > > > Phones that need access to the VOIP PBX at Office 1

    >
    > > > Here's what I was hoping to do:

    >
    > > > VLAN for servers
    > > > VLAN for PCs at Office 1
    > > > VLAN for PCs at Office 2
    > > > VLAN for VOIP stuff

    >
    > > > I was hoping to use the 3560 to statically route between the VLANs at
    > > > the offices by sending the traffic to the specific switchport.
    > > > So as an example the 3560 in Office 2 would have the server VLAN setup
    > > > and then have a route to the P-T-P switchport, etc..
    > > > Apparently this may not be possible.

    >
    > > > What additional hw/reorganization would I need to make it possible?

    >
    > > > Thanks.

    >
    > > OK, I think I understand what you're wanting to do now. If your
    > > switches support a dynamic routing protocol (even RIP should probably
    > > work OK in this case), it might make it a bit easier to configure
    > > because you wouldn't have to worry about tons of static routes.

    >
    > > The only places you have to worry about the VLAN's is on the 3560's.
    > > You only have to set up the local VLAN's on the local switch. So, the
    > > 3560 @ office 1 just needs Office 1's VLAN's added to its VLAN
    > > databaset. And the same for office 2.

    >
    > > You just have to configure the 3560's to route between those local
    > > VLAN's, and to have the attached router as its default gateway. Then,
    > > you have to set up static routes on the routers. So, office 1's
    > > router would have static routes to all of the office 1 VLAN's with the
    > > 3560's IP as the next hop. And office 2's router would have static
    > > routes to all of the office 2 VLAN's with the 3560 at office 2 as the
    > > next hop. Then on your routers you should set up static routes to the
    > > other office's VLAN's. You would add static routes on office 1's
    > > router to all of the VLAN's at office 2 with the office 2 router as
    > > the next hop and vice versa.

    >
    > > You should try to use a dynamic routing protocol if you can, it'll
    > > make it easier to configure, and easier to change your network
    > > structure later on. I think the 3560's should support RIP even if
    > > they have SMI, and RIP should work OK in this case. If you are using
    > > RIP, then you should just add each of the local VLAN's networks to RIP
    > > on each of the 3560's. And just add the networks (ie, the serial link
    > > and link to the 3560) that are directly connected to the routers to
    > > RIP on the routers at each office. And make sure RIP is enabled for
    > > all of the appropriate interfaces. If you have EMI on your 3560's,
    > > then I think you are even be able to use EIGRP or OSPF or something
    > > much more modern than RIP.

    >
    > > Hope that helps a little,

    >
    > > Oliver

    >
    > Thanks Oliver.
    > The only caveat is that I don't have another router @ Office 1 - right
    > now it's just a 1720 with a WIC card for the existing T1.
    > Cisco seems to insist that the following configuration works with
    > bridging:
    >
    > 3560 -> 2851 -> p-t-p T1 -> Adtran CSU/DSU -> 3560.
    > Have you ever heard of that?
    >
    > -- James
     
    , Sep 21, 2007
    #7
    1. Advertising

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