Default router issue

Discussion in 'Cisco' started by Charles N Wyble, Jun 3, 2008.

  1. So I have a strange issue with my 1841. I'm using it in a very simple
    scenario (home router on DSL line).

    For some reason the router of last resort only gets set if I set
    FastEthernet0/1 address via dhcp. If I set it statically and then set
    router of last resort it doesn't show in show run config.

    Anyone seen something like this? Is it a known bug in a slightly
    outdated version of IOS?

    ROM: System Bootstrap, Version 12.3(8r)T6, RELEASE SOFTWARE (fc1)

    I haven't read through all of the release notes for later versions of
    IOS. Is that where I should look to see bug notices or is there some
    place else I should check for that?

    Thanks!

    Charles
     
    Charles N Wyble, Jun 3, 2008
    #1
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  2. Charles N Wyble

    Sam Wilson Guest

    In article <A261k.470$>,
    Charles N Wyble <> wrote:

    > So I have a strange issue with my 1841. I'm using it in a very simple
    > scenario (home router on DSL line).
    >
    > For some reason the router of last resort only gets set if I set
    > FastEthernet0/1 address via dhcp. If I set it statically and then set
    > router of last resort it doesn't show in show run config.
    >
    > Anyone seen something like this? Is it a known bug in a slightly
    > outdated version of IOS?
    >
    > ROM: System Bootstrap, Version 12.3(8r)T6, RELEASE SOFTWARE (fc1)
    >
    > I haven't read through all of the release notes for later versions of
    > IOS. Is that where I should look to see bug notices or is there some
    > place else I should check for that?


    If you set the Fa0/1 address manually are you also setting a default
    route? If not then there won't be one. A DHCP server will usually
    provide a default gateway as well as an IP address (as well a whole
    bunch of other stuff).

    Sam
     
    Sam Wilson, Jun 3, 2008
    #2
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  3. Charles N Wyble

    Trendkill Guest

    On Jun 3, 5:28 am, Sam Wilson <> wrote:
    > In article <A261k.470$>,
    > Charles N Wyble <> wrote:
    >
    > > So I have a strange issue with my 1841. I'm using it in a very simple
    > > scenario (home router on DSL line).

    >
    > > For some reason the router of last resort only gets set if I set
    > > FastEthernet0/1 address via dhcp. If I set it statically and then set
    > > router of last resort it doesn't show in show run config.

    >
    > > Anyone seen something like this? Is it a known bug in a slightly
    > > outdated version of IOS?

    >
    > > ROM: System Bootstrap, Version 12.3(8r)T6, RELEASE SOFTWARE (fc1)

    >
    > > I haven't read through all of the release notes for later versions of
    > > IOS. Is that where I should look to see bug notices or is there some
    > > place else I should check for that?

    >
    > If you set the Fa0/1 address manually are you also setting a default
    > route? If not then there won't be one. A DHCP server will usually
    > provide a default gateway as well as an IP address (as well a whole
    > bunch of other stuff).
    >
    > Sam


    Sam is right on point, if you are not running a routing protocol with
    the provider (which is never done on Residential service), then you
    router is getting its default gateway from the DHCP process. DHCP can
    provide many extra fields beyond an IP and Subnet Mask, such as DNS
    servers, default gateways, and tftp servers. As soon as you set a
    static, you must provide these variables on your own to each node on
    that same subnetwork (in this case, probably only your router, and DNS/
    TFTP are probably not needed).
     
    Trendkill, Jun 3, 2008
    #3
  4. Sam Wilson wrote:
    >>
    >> For some reason the router of last resort only gets set if I set
    >> FastEthernet0/1 address via dhcp. If I set it statically and then set
    >> router of last resort it doesn't show in show run config.
    >>
    >> Anyone seen something like this? Is it a known bug in a slightly
    >> outdated version of IOS?
    >>
    >> ROM: System Bootstrap, Version 12.3(8r)T6, RELEASE SOFTWARE (fc1)
    >>
    >> I haven't read through all of the release notes for later versions of
    >> IOS. Is that where I should look to see bug notices or is there some
    >> place else I should check for that?

    >
    > If you set the Fa0/1 address manually are you also setting a default
    > route?


    Ah good point. I set the gateway but not the default route.

    If not then there won't be one. A DHCP server will usually
    > provide a default gateway as well as an IP address (as well a whole
    > bunch of other stuff).


    Yes I know that. :) I have configured many DHCP servers/setups.

    Thanks for the insight!

    Charles
     
    Charles N Wyble, Jun 3, 2008
    #4
  5. Charles N Wyble

    Sam Wilson Guest

    In article <gnf1k.3697$>,
    Charles N Wyble <> wrote:

    > Sam Wilson wrote:
    > >
    > > If you set the Fa0/1 address manually are you also setting a default
    > > route?

    >
    > Ah good point. I set the gateway but not the default route.


    You may know this as well, but "ip default-gateway" isn't the same as a
    default route - IIRC it's only used when the box isn't configured as a
    router.

    Sam
     
    Sam Wilson, Jun 3, 2008
    #5
  6. Sam Wilson wrote:
    > In article <gnf1k.3697$>,
    > Charles N Wyble <> wrote:
    >
    >> Sam Wilson wrote:
    >>> If you set the Fa0/1 address manually are you also setting a default
    >>> route?

    >> Ah good point. I set the gateway but not the default route.

    >
    > You may know this as well, but "ip default-gateway" isn't the same as a
    > default route


    Right.... that makes sense.

    - IIRC it's only used when the box isn't configured as a
    > router.


    As far as I can tell, its used when the router isn't the last hop. I
    could be wrong though. :)

    Charles
     
    Charles N Wyble, Jun 3, 2008
    #6
  7. Charles N Wyble

    Sam Wilson Guest

    In article <ryg1k.2526$>,
    Charles N Wyble <> wrote:

    > Sam Wilson wrote:
    > > In article <gnf1k.3697$>,
    > > Charles N Wyble <> wrote:
    > >
    > >> Sam Wilson wrote:
    > >>> If you set the Fa0/1 address manually are you also setting a default
    > >>> route?
    > >> Ah good point. I set the gateway but not the default route.

    > >
    > > You may know this as well, but "ip default-gateway" isn't the same as a
    > > default route

    >
    > Right.... that makes sense.
    >
    > > - IIRC it's only used when the box isn't configured as a
    > > router.

    >
    > As far as I can tell, its used when the router isn't the last hop. I
    > could be wrong though. :)


    I don't think that's right. "ip default-gateway" is used when the box
    isn't being a router: either it's a switch and not a router at all, or
    you have a router being a bridge, or at least not an IP router, or
    during flash load helper (where a run-from-flash box is running a
    stripped down IOS while replacing the main IOS code).

    Sam
     
    Sam Wilson, Jun 3, 2008
    #7
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