Cisco 1721 static routing

Discussion in 'Cisco' started by Larry, May 14, 2005.

  1. Larry

    Larry Guest

    Forgive me if this is a stupid question...

    We are a small company and have a 1721 that is the gateway to
    our provider for our Internet service. We are currently not
    using any routing protocols and have 1 static route to our
    provider. I now have the need to add a ethernet card in the
    extra slot to route to another company temporarily. The company
    is located in the same building so it should be easy but since
    I'm saavy I need to make sure I'm doing things right.

    Currently the routing info looks like the following:

    iproute 0.0.0.0 0.0.0.0 65.65.xxx.xxx
    Which is our ISP's router.

    Assuming the other parties end of the connection is 172.16.17.1,
    and I configure the address of Eth0 to 172.16.17.2, is this as
    simple as adding the line:

    iproute 172.16.17.0 0.0.0.255 172.16.17.2

    Are routes processed in order like ACL's? Does the new route
    need to be first to be processed correctly?

    Thanks for your help.
    Larry
     
    Larry, May 14, 2005
    #1
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  2. In article <Xns9655C63074D5Anone@69.28.186.121>,
    Larry <> wrote:
    :Forgive me if this is a stupid question...

    Not stupid at all, just something that'll become second nature with
    a bit of experience with the device.


    :We are a small company and have a 1721 that is the gateway to
    :eek:ur provider for our Internet service. We are currently not
    :using any routing protocols and have 1 static route to our
    :provider. I now have the need to add a ethernet card in the
    :extra slot to route to another company temporarily. The company
    :is located in the same building so it should be easy but since
    :I'm saavy I need to make sure I'm doing things right.

    :Currently the routing info looks like the following:

    :iproute 0.0.0.0 0.0.0.0 65.65.xxx.xxx
    :Which is our ISP's router.

    :Assuming the other parties end of the connection is 172.16.17.1,
    :and I configure the address of Eth0 to 172.16.17.2, is this as
    :simple as adding the line:

    :iproute 172.16.17.0 0.0.0.255 172.16.17.2

    It's even simpler than that: you don't have to add any ip route
    statement at all. As soon as you assign the IP address and mask to the
    interface, the router will automatically add in a route out
    the Eth0 interface for all of 172.16.17.*. The devices at the
    other end of the link will take care of the rest.


    :Are routes processed in order like ACL's? Does the new route
    :need to be first to be processed correctly?

    Routes are processed as "longest match" first. Any traffic
    to 172.16.17 will match 24 bits to the automatic "connected" route
    that the router will put in for you, whereas traffic to other
    locations will not match that same prefix and will match only the
    0-bits long default route that you have.

    The more specific a route entry, the higher it's precidence; the
    order of the routing statements in the configuration doesn't matter.
    [Not, that is, until you get into policy based routing.]


    Note: the above, saying that you don't need to add a route at all,
    presumes that the other end is not using a router between you and
    them. If they -are- using a router in between, then a route
    statement would be needed... e.g.,

    ip route 172.16.18.0 255.255.255.0 172.16.17.1

    {I'm going to skip the paragraphs of explaining that...}
    --
    "This was a Golden Age, a time of high adventure, rich living and
    hard dying... but nobody thought so." -- Alfred Bester, TSMD
     
    Walter Roberson, May 14, 2005
    #2
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  3. Larry

    Guest

    Are you sure the 1721 supports an extra LAN card? My understanding is
    that those 2 WIC slots are WAN WIC for WAN modules.

    http://www.cisco.com/en/US/products/hw/routers/ps221/products_data_sheet09186a00800920ec.html

    http://www.cisco.com/en/US/products/hw/routers/ps221/products_relevant_interfaces_and_modules.html

    Let's get back to your original question. If your partner is
    responsible for NAT'ting their networks, then your serial1 would
    172.16.17.2/24. You need not a static route to their network (same
    subnet).

    If they are not responible for NAT, AND their internal network that you
    want to access is 172.16.17.0/24, then you and your partner will need
    to agree to a new subnet (e.g. your serial1 is 172.16.18.2/30 and
    theirs is 172.16.18.1/30), and you'll set up a static route of together
    with the existing default route:

    ip route 172.16.17.0 255.255.255.0 172.16.18.1
    ip route 0.0.0.0 0.0.0.0 65.65.xx.xx (already existed, no need to
    re-enter)

    Anything destination that does not match 172.16.17.0/24 and your
    internal networks would be routed to 65.65.xx.xx.

    "Route Selection in Cisco Routers"
    http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094823.shtml

    hktco

    Larry wrote:
    > Forgive me if this is a stupid question...
    >
    > We are a small company and have a 1721 that is the gateway to
    > our provider for our Internet service. We are currently not
    > using any routing protocols and have 1 static route to our
    > provider. I now have the need to add a ethernet card in the
    > extra slot to route to another company temporarily. The company
    > is located in the same building so it should be easy but since
    > I'm saavy I need to make sure I'm doing things right.
    >
    > Currently the routing info looks like the following:
    >
    > iproute 0.0.0.0 0.0.0.0 65.65.xxx.xxx
    > Which is our ISP's router.
    >
    > Assuming the other parties end of the connection is 172.16.17.1,
    > and I configure the address of Eth0 to 172.16.17.2, is this as
    > simple as adding the line:
    >
    > iproute 172.16.17.0 0.0.0.255 172.16.17.2
    >
    > Are routes processed in order like ACL's? Does the new route
    > need to be first to be processed correctly?
    >
    > Thanks for your help.
    > Larry
     
    , May 14, 2005
    #3
  4. In article <>,
    <> wrote:
    :Are you sure the 1721 supports an extra LAN card? My understanding is
    :that those 2 WIC slots are WAN WIC for WAN modules.

    That's a good question; you merely happened to have overlooked the
    WIC-1ENET One-port 10BASE-T Ethernet interface .

    Since they don't need to use VLANs on the link, and they
    are not trying to bridge the two ethernet interfaces,
    a "WAN" ethernet interface is the same as a "LAN" ethernet interface
    to them.
    --
    Ceci, ce n'est pas une idée.
     
    Walter Roberson, May 14, 2005
    #4
  5. Larry

    Larry Guest

    -cnrc.gc.ca (Walter Roberson) wrote in
    news:d63j59$jt9$:

    > In article <Xns9655C63074D5Anone@69.28.186.121>,
    > Larry <> wrote:
    >:Forgive me if this is a stupid question...
    >
    > Not stupid at all, just something that'll become second
    > nature with a bit of experience with the device.
    >
    >
    >:We are a small company and have a 1721 that is the gateway
    >:to our provider for our Internet service. We are currently
    >:not using any routing protocols and have 1 static route to
    >:eek:ur provider. I now have the need to add a ethernet card in
    >:the extra slot to route to another company temporarily. The
    >:company is located in the same building so it should be
    >:easy but since I'm saavy I need to make sure I'm doing
    >:things right.
    >
    >:Currently the routing info looks like the following:
    >
    >:iproute 0.0.0.0 0.0.0.0 65.65.xxx.xxx
    >:Which is our ISP's router.
    >
    >:Assuming the other parties end of the connection is
    >:172.16.17.1, and I configure the address of Eth0 to
    >:172.16.17.2, is this as simple as adding the line:
    >
    >:iproute 172.16.17.0 0.0.0.255 172.16.17.2
    >
    > It's even simpler than that: you don't have to add any ip
    > route statement at all. As soon as you assign the IP
    > address and mask to the interface, the router will
    > automatically add in a route out the Eth0 interface for all
    > of 172.16.17.*. The devices at the other end of the link
    > will take care of the rest.
    >
    >
    >:Are routes processed in order like ACL's? Does the new
    >:route need to be first to be processed correctly?
    >
    > Routes are processed as "longest match" first. Any traffic
    > to 172.16.17 will match 24 bits to the automatic
    > "connected" route that the router will put in for you,
    > whereas traffic to other locations will not match that same
    > prefix and will match only the 0-bits long default route
    > that you have.
    >
    > The more specific a route entry, the higher it's
    > precidence; the order of the routing statements in the
    > configuration doesn't matter. [Not, that is, until you get
    > into policy based routing.]
    >
    >
    > Note: the above, saying that you don't need to add a route
    > at all, presumes that the other end is not using a router
    > between you and them. If they -are- using a router in
    > between, then a route statement would be needed... e.g.,
    >
    > ip route 172.16.18.0 255.255.255.0 172.16.17.1
    >
    > {I'm going to skip the paragraphs of explaining that...}


    Very helpful... Thank you sir! Interesting to note that the
    mask for "iproute" is the same as a mask for your ip config on
    your PC. It's those details that keep me mixed up. I have a
    very detailed ACL that I use to help keep the garbage away
    from the firewall and the masks are just he opposite.

    Again much thanks.

    Larry
     
    Larry, May 14, 2005
    #5
  6. Larry

    Larry Guest

    wrote in
    news::

    > Are you sure the 1721 supports an extra LAN card? My
    > understanding is that those 2 WIC slots are WAN WIC for WAN
    > modules.


    Absolutely positive. It is only 10BaseT but that is sufficient
    for our needs. We have used this router in just this scenario
    a couple of years ago which is why I chose this path, we
    already have the hardware.

    >
    > Let's get back to your original question. If your partner
    > is responsible for NAT'ting their networks, then your
    > serial1 would 172.16.17.2/24. You need not a static route
    > to their network (same subnet).
    >

    That is exactly the case so I should not need to add anything
    over what is automatically added when configuring the
    interface.

    >
    > Anything destination that does not match 172.16.17.0/24 and
    > your internal networks would be routed to 65.65.xx.xx.
    >
    > "Route Selection in Cisco Routers"
    > http://www.cisco.com/en/US/tech/tk365/technologies_tech_note
    > 09186a0080094823.shtml


    I'll follow-up on that link in the morning.

    >
    >
    > Larry wrote:
    >> Forgive me if this is a stupid question...
    >>
    >> We are a small company and have a 1721 that is the gateway
    >> to our provider for our Internet service. We are currently
    >> not using any routing protocols and have 1 static route to
    >> our provider. I now have the need to add a ethernet card
    >> in the extra slot to route to another company temporarily.
    >> The company is located in the same building so it should
    >> be easy but since I'm saavy I need to make sure I'm doing
    >> things right.
    >>
    >> Currently the routing info looks like the following:
    >>
    >> iproute 0.0.0.0 0.0.0.0 65.65.xxx.xxx
    >> Which is our ISP's router.
    >>
    >> Assuming the other parties end of the connection is
    >> 172.16.17.1, and I configure the address of Eth0 to
    >> 172.16.17.2, is this as simple as adding the line:
    >>
    >> iproute 172.16.17.0 0.0.0.255 172.16.17.2
    >>
    >> Are routes processed in order like ACL's? Does the new
    >> route need to be first to be processed correctly?
    >>
    >> Thanks for your help.
    >> Larry

    >


    Thanks again!
     
    Larry, May 14, 2005
    #6
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