Lan routing - 2 subnets using single fast ethernet port

Discussion in 'Cisco' started by AlexC, Oct 16, 2003.

  1. AlexC

    AlexC Guest

    Hi,

    I thinking of doing simple lan routing for 2 subnets, I'm also
    thinking
    of getting a cisco 1721 as the router, I plan to put the fast ethernet
    port on the subnet A, then create a sub-interface on subnet B.


    cisco 1721
    |
    |
    |
    +---------------------+
    | |
    | 4 port switch |
    | |
    +---------------------+
    | |
    | |
    | |
    subnet A subnet B ( 20 Nodes)
    (about 30 Nodes)


    I tested this scenario with a Linux(with only 1 NIC). What i did was
    make eth0 IP sits on subnet A, and eth0:0 sits on subnet B, and let
    them be the default gateway for respecetive subnet nodes, it works
    perfectly.

    Now my question is, will this work on the Cisco 1721? (i believe it
    should
    be, just playing safe :) )

    Also, by using only 1 fast ethernet port, will this create bottleneck
    or performance issue?


    Thanks
     
    AlexC, Oct 16, 2003
    #1
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  2. AlexC

    Mike Guest

    I don't believe it will. I believe that you need at least a 1751. I
    don't think the 172x supports trunking and that's what you need for
    router on a stick. I think. It also depends on the switch, can you
    configure a port to trunk.

    When you bonded two addresses to your single physical NIC you still
    only had one collision domain.

    If all you want to do is replicate what the Linux box was doing then
    you can do it with a 1721. You would just apply a "secondary" ip
    address to the ethernet interface.

    I think

    On 15 Oct 2003 19:09:36 -0700, (AlexC) wrote:

    >Hi,
    >
    >I thinking of doing simple lan routing for 2 subnets, I'm also
    >thinking
    >of getting a cisco 1721 as the router, I plan to put the fast ethernet
    >port on the subnet A, then create a sub-interface on subnet B.
    >
    >
    > cisco 1721
    > |
    > |
    > |
    >+---------------------+
    >| |
    >| 4 port switch |
    >| |
    >+---------------------+
    > | |
    > | |
    > | |
    > subnet A subnet B ( 20 Nodes)
    >(about 30 Nodes)
    >
    >
    >I tested this scenario with a Linux(with only 1 NIC). What i did was
    >make eth0 IP sits on subnet A, and eth0:0 sits on subnet B, and let
    >them be the default gateway for respecetive subnet nodes, it works
    >perfectly.
    >
    >Now my question is, will this work on the Cisco 1721? (i believe it
    >should
    >be, just playing safe :) )
    >
    >Also, by using only 1 fast ethernet port, will this create bottleneck
    >or performance issue?
    >
    >
    >Thanks
     
    Mike, Oct 16, 2003
    #2
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  3. AlexC

    AlexC Guest

    > If all you want to do is replicate what the Linux box was doing then
    > you can do it with a 1721. You would just apply a "secondary" ip
    > address to the ethernet interface.


    does that mean it can be done uing 1721? Would it create a bottleneck
    on network throuput?
     
    AlexC, Oct 16, 2003
    #3
  4. In article <>,
    AlexC <> wrote:
    >> If all you want to do is replicate what the Linux box was doing then
    >> you can do it with a 1721. You would just apply a "secondary" ip
    >> address to the ethernet interface.

    >
    >does that mean it can be done uing 1721? Would it create a bottleneck
    >on network throuput?


    Configure "ip route-cache same-interface" and there shouldn't be any
    performance impact.

    --
    Barry Margolin,
    Level(3), Woburn, MA
    *** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to newsgroups.
    Please DON'T copy followups to me -- I'll assume it wasn't posted to the group.
     
    Barry Margolin, Oct 16, 2003
    #4
  5. AlexC

    AlexC Guest

    > Configure "ip route-cache same-interface" and there shouldn't be any
    > performance impact.


    that is something new to me, btw I also spotted another low end model
    Cisco 837, which has 4 ethernet ports. Anyone know if these 4 ports
    can be configure different IPs on each interface? like

    interface Ethernet0
    .....
    interface Ethernet1
    ....
    interface Ethernet2
    ....
    interface Ethernet3
    ....


    ???



    Barry Margolin <> wrote in message news:<Nvyjb.66$3.com>...
    > In article <>,
    > AlexC <> wrote:
    > >> If all you want to do is replicate what the Linux box was doing then
    > >> you can do it with a 1721. You would just apply a "secondary" ip
    > >> address to the ethernet interface.

    > >
    > >does that mean it can be done uing 1721? Would it create a bottleneck
    > >on network throuput?

    >
     
    AlexC, Oct 17, 2003
    #5
  6. In article <>,
    AlexC <> wrote:
    >> Configure "ip route-cache same-interface" and there shouldn't be any
    >> performance impact.

    >
    >that is something new to me, btw I also spotted another low end model
    >Cisco 837, which has 4 ethernet ports. Anyone know if these 4 ports
    >can be configure different IPs on each interface? like


    Of course they can, that's the normal way that routers are used.

    --
    Barry Margolin,
    Level(3), Woburn, MA
    *** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to newsgroups.
    Please DON'T copy followups to me -- I'll assume it wasn't posted to the group.
     
    Barry Margolin, Oct 17, 2003
    #6
  7. In article <vKTjb.87$3.com>,
    Barry Margolin <> wrote:
    > In article <>,
    > AlexC <> wrote:
    > >> Configure "ip route-cache same-interface" and there shouldn't be any
    > >> performance impact.

    > >
    > >that is something new to me, btw I also spotted another low end model
    > >Cisco 837, which has 4 ethernet ports. Anyone know if these 4 ports
    > >can be configure different IPs on each interface? like

    >
    > Of course they can, that's the normal way that routers are used.


    On the 837, I believe the four Ethernet ports are four ports of a built-in
    10/100 Ethernet switch, therefore only a single L3 interface would be
    available in the router's configuration.

    Cheers,

    Matt

    --
    Matthew Melbourne
     
    Matthew Melbourne, Oct 17, 2003
    #7
  8. AlexC

    AlexC Guest

    I suddenly realize that the single port solution might not work if
    we need to use DHCP to assign IP address to these 2 different networks,
    we simple wont be able know which nodes "should" belong to which network
    as the DHCP request will all come in via the same internet to the router,
    anybody deal with this problem before?


    Barry Margolin <> wrote in message news:<vKTjb.87$3.com>...
    > In article <>,
    > AlexC <> wrote:
    > >> Configure "ip route-cache same-interface" and there shouldn't be any
    > >> performance impact.

    > >
    > >that is something new to me, btw I also spotted another low end model
    > >Cisco 837, which has 4 ethernet ports. Anyone know if these 4 ports
    > >can be configure different IPs on each interface? like

    >
    > Of course they can, that's the normal way that routers are used.
     
    AlexC, Oct 20, 2003
    #8
  9. AlexC

    Ivan Ostres Guest

    "AlexC" <> wrote in message
    news:...
    > I suddenly realize that the single port solution might not work if
    > we need to use DHCP to assign IP address to these 2 different networks,
    > we simple wont be able know which nodes "should" belong to which network
    > as the DHCP request will all come in via the same internet to the router,
    > anybody deal with this problem before?
    >
    >


    Yes, that is a common problem. Most of the time, people don't really care
    which host gets address from which subnet. For hosts that need always the
    same address, it's a better solution to set static addresses anyway...

    Ivan
     
    Ivan Ostres, Oct 20, 2003
    #9
  10. AlexC

    Andre Beck Guest

    Matthew Melbourne <> writes:
    >
    > On the 837, I believe the four Ethernet ports are four ports of a built-in
    > 10/100 Ethernet switch, therefore only a single L3 interface would be
    > available in the router's configuration.


    On a 836 testing 12.3(3)XM (or something like that), four new interfaces
    (FastEthernet1 - 4) appeared all of a sudden. The Ethernet0 remained
    as a routed interface. I didn't investigate further whether this was just
    done so you can modify individual switchport characteristics, or whether
    this would allow to turn them into routed ports. Enabling HSRP on this
    boxes e0 broke tunneling badly (Fa1 went down and up again when the HSRP
    group switched to this box, and at the same time, all tunnels with a
    source address borrowed from e0 just died), so I didn't really feel to
    push it any further.

    --
    The _S_anta _C_laus _O_peration
    or "how to turn a complete illusion into a neverending money source"

    -> Andre "ABPSoft" Beck +++ ABP-RIPE +++ Dresden, Germany, Spacetime <-
     
    Andre Beck, Oct 23, 2003
    #10
  11. AlexC

    reena_ahuja24

    Joined:
    Feb 27, 2009
    Messages:
    1
    hi

    I want to know how to connect 2 different subnet through LAN card only without cisco router.and i want to know configuration of this simple scenario.

    Regards,
    REena Ahuja
     
    reena_ahuja24, Feb 28, 2009
    #11
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