How do I forward/handle this routing change?

Discussion in 'Cisco' started by dxt178, Jan 25, 2007.

  1. dxt178

    dxt178 Guest

    Currently our users rely on a front-end that is pointing to a server
    that resides inside of our lan (say 10.0.0.6) and it is configured in
    the application to that IP. We are outsourcing this server (say
    192.168.1.2) via a dedicated link handled by a small Cisco 1700 (with
    an IP of 10.0.0.240) router that is physically located at our location
    that they manage.

    Currently my internal routers are set to route all other traffic
    destined for 192.168.1.2 via 10.0.0.240 and then it winds its way onto
    the new server which works. (they have the statement: "ip route
    192.168.1.2 255.255.255.255 10.0.0.240")

    I need to come up with a way to redirect the traffic destined for
    10.0.0.6 coming from this front-end to the IP 192.168.1.2 and so that
    it goes out via 10.0.0.240 without manually touching each machine and
    changing it to point to 192.168.1.2.

    I had tried a route statement of "ip route 10.0.0.6 255.255.255.255
    192.168.1.2" but that results in a loop where the traffic just bounces
    around on the router since there is no 10.0.0.6 on their side.

    Should I just have them put a route in their router to then handle
    forwarding that traffic on to their server, or is there a way for me
    to handle this all on my side of the network so no changes need to be
    made on their router?

    Thanks,
    Dominic
    dxt178, Jan 25, 2007
    #1
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  2. dxt178

    Mike Rahl Guest

    I believe you are correct in that specifying a static route to a
    destination that does not exist and is not known on the next hop router
    could create a routing loop.

    If I understand this correctly, you are attempting to redirect traffic
    which all your PCs using this application used to send to an address of
    10.0.0.6 now to an address of 192.168.1.2.

    Have you considered setting up a Network Address Translation? From
    what I'm understanding here, you have the following design:

    original design:

    ======== ----> =========
    PCs server
    10.0.0.0/24 10.0.0.6/24

    New Design

    ======== ========= ----> =========== ------>
    ============
    PCs your router provider router
    server
    10.0.0.0/24 10.0.0.0/24 192.168.1.0/24
    192.168.1.2


    If you were to instead, on the router you use to communicate with your
    outsourcing company's Cisco 1700 router, set up a Network address
    translation, so that your 10.0.0.x machines would send packets to
    10.0.0.6 which would then be NATted to 192.168.1.2, this might work.
    It would depend on if the server was originally located on the same
    subnet or not, I suspect

    On Jan 25, 9:54 am, "dxt178" <> wrote:
    > Currently our users rely on a front-end that is pointing to a server
    > that resides inside of our lan (say 10.0.0.6) and it is configured in
    > the application to that IP. We are outsourcing this server (say
    > 192.168.1.2) via a dedicated link handled by a small Cisco 1700 (with
    > an IP of 10.0.0.240) router that is physically located at our location
    > that they manage.
    >
    > Currently my internal routers are set to route all other traffic
    > destined for 192.168.1.2 via 10.0.0.240 and then it winds its way onto
    > the new server which works. (they have the statement: "ip route
    > 192.168.1.2 255.255.255.255 10.0.0.240")
    >
    > I need to come up with a way to redirect the traffic destined for
    > 10.0.0.6 coming from this front-end to the IP 192.168.1.2 and so that
    > it goes out via 10.0.0.240 without manually touching each machine and
    > changing it to point to 192.168.1.2.
    >
    > I had tried a route statement of "ip route 10.0.0.6 255.255.255.255
    > 192.168.1.2" but that results in a loop where the traffic just bounces
    > around on the router since there is no 10.0.0.6 on their side.
    >
    > Should I just have them put a route in their router to then handle
    > forwarding that traffic on to their server, or is there a way for me
    > to handle this all on my side of the network so no changes need to be
    > made on their router?
    >
    > Thanks,
    > Dominic
    Mike Rahl, Jan 25, 2007
    #2
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  3. dxt178

    dxt178 Guest

    Amazingly you did understand my question quite well :) NAT may be a
    possibility, I wasn't thinking in that direction because I was
    aproaching it solely as a routing problem. I kind of don't understand
    your last bit about the server originally being on the same subnet or
    not... if you'd have a second to explain that to me I'd appreciate it.

    If I NAT 10.0.0.6 traffic to 192.168.1.2 then the existing IP route on
    my side pointing that traffic to 10.0.0.240 would stay and work fine.
    They would not need to update their router because when the traffic
    hits it it appears just as the rest of the traffic destined for
    192.168.1.2 that already routes fine.

    That sounds like a valid plan, I'm going to test it out now.

    Thanks!
    Dominic

    On Jan 25, 10:18 am, "Mike Rahl" <> wrote:
    > I believe you are correct in that specifying a static route to a
    > destination that does not exist and is not known on the next hop router
    > could create a routing loop.
    >
    > If I understand this correctly, you are attempting to redirect traffic
    > which all your PCs using this application used to send to an address of
    > 10.0.0.6 now to an address of 192.168.1.2.
    >
    > Have you considered setting up a Network Address Translation? From
    > what I'm understanding here, you have the following design:
    >
    > original design:
    >
    > ======== ----> =========
    > PCs server
    > 10.0.0.0/24 10.0.0.6/24
    >
    > New Design
    >
    > ======== ========= ----> =========== ------>
    > ============
    > PCs your router provider router
    > server
    > 10.0.0.0/24 10.0.0.0/24 192.168.1.0/24
    > 192.168.1.2
    >
    > If you were to instead, on the router you use to communicate with your
    > outsourcing company's Cisco 1700 router, set up a Network address
    > translation, so that your 10.0.0.x machines would send packets to
    > 10.0.0.6 which would then be NATted to 192.168.1.2, this might work.
    > It would depend on if the server was originally located on the same
    > subnet or not, I suspect
    >
    > On Jan 25, 9:54 am, "dxt178" <> wrote:
    >
    > > Currently our users rely on a front-end that is pointing to a server
    > > that resides inside of our lan (say 10.0.0.6) and it is configured in
    > > the application to that IP. We are outsourcing this server (say
    > > 192.168.1.2) via a dedicated link handled by a small Cisco 1700 (with
    > > an IP of 10.0.0.240) router that is physically located at our location
    > > that they manage.

    >
    > > Currently my internal routers are set to route all other traffic
    > > destined for 192.168.1.2 via 10.0.0.240 and then it winds its way onto
    > > the new server which works. (they have the statement: "ip route
    > > 192.168.1.2 255.255.255.255 10.0.0.240")

    >
    > > I need to come up with a way to redirect the traffic destined for
    > > 10.0.0.6 coming from this front-end to the IP 192.168.1.2 and so that
    > > it goes out via 10.0.0.240 without manually touching each machine and
    > > changing it to point to 192.168.1.2.

    >
    > > I had tried a route statement of "ip route 10.0.0.6 255.255.255.255
    > > 192.168.1.2" but that results in a loop where the traffic just bounces
    > > around on the router since there is no 10.0.0.6 on their side.

    >
    > > Should I just have them put a route in their router to then handle
    > > forwarding that traffic on to their server, or is there a way for me
    > > to handle this all on my side of the network so no changes need to be
    > > made on their router?

    >
    > > Thanks,
    > > Dominic
    dxt178, Jan 25, 2007
    #3
  4. dxt178

    JF Mezei Guest

    dxt178 wrote:
    > aproaching it solely as a routing problem. I kind of don't understand
    > your last bit about the server originally being on the same subnet or
    > not... if you'd have a second to explain that to me I'd appreciate it.



    If client 10.0.0.27 with netmask of 255.0.0.0 attempts to connect to
    10.0.0.6, it expects 10.0.0.6 to be located in the same LAN and will send
    out ARP packets to try to find its ethernet address and communicate
    locally. If there is nobody to respond to ARP requests for 10.0.0.6, then
    the client will declare a failure to reach 10.0.0.6.

    So you would have to configure your router to somehow respond to ARP
    requests for 10.0.0.6 as well as its own address, or artificially inject
    ARP entries in each client to point 10.0.0.6 to the router.


    Not sure if this would work, but adding static routes in each client might
    be able to force 10.0.0.6 to be routed to the router instead of being
    handled as an IP in the same subnet.
    JF Mezei, Jan 25, 2007
    #4
  5. dxt178

    dxt178 Guest

    Ahh, I see what your saying... but I guess how I get lucky with this
    one is that the router containing the route statements I mentioned is
    also the default gateway for all the individual PC's. I believe that is
    why.

    I was attempting to set up NAT but it appears the IOS (11.3) version of
    this router doesn't support it. It allowed me to define "ip nat inside"
    but when I tried to add "ip nat inside source static..." it gave an
    error at the word static... so i'm guessing the older IOS has a
    different syntax. (?)

    Dominic

    On Jan 25, 6:32 pm, JF Mezei <> wrote:
    > dxt178 wrote:
    > > aproaching it solely as a routing problem. I kind of don't understand
    > > your last bit about the server originally being on the same subnet or
    > > not... if you'd have a second to explain that to me I'd appreciate it.If client 10.0.0.27 with netmask of 255.0.0.0 attempts to connect to

    > 10.0.0.6, it expects 10.0.0.6 to be located in the same LAN and will send
    > out ARP packets to try to find its ethernet address and communicate
    > locally. If there is nobody to respond to ARP requests for 10.0.0.6, then
    > the client will declare a failure to reach 10.0.0.6.
    >
    > So you would have to configure your router to somehow respond to ARP
    > requests for 10.0.0.6 as well as its own address, or artificially inject
    > ARP entries in each client to point 10.0.0.6 to the router.
    >
    > Not sure if this would work, but adding static routes in each client might
    > be able to force 10.0.0.6 to be routed to the router instead of being
    > handled as an IP in the same subnet.
    dxt178, Jan 26, 2007
    #5
  6. dxt178

    JF Mezei Guest

    dxt178 wrote:
    > Ahh, I see what your saying... but I guess how I get lucky with this
    > one is that the router containing the route statements I mentioned is
    > also the default gateway for all the individual PC's. I believe that is
    > why.


    Your individial PCs will not send be sending packets to the router if they
    think that 10.0.0.6 is part of their local subnet.

    You'll have to get your router to answer to ARP requests for 10.0.0.6 for
    this to work. Not sure if it is legal, but if you create an interface with
    ip 10.0.0.6/32 , that would cause the router to reply to ARP requests for
    that IP. But it might conflict with the router's real IP for that subnet.
    JF Mezei, Jan 27, 2007
    #6
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