From: Michael Zuo (mzuo@ixiacom.com)
Date: Fri Feb 23 2007 - 02:44:52 ART
From the DocCD:
"
The ip directed-broadcast command controls the explosion of directed
broadcasts when they reach their target subnets. The command affects
only the final transmission of the directed broadcast on its ultimate
destination subnet. It does not affect the transit unicast routing of IP
directed broadcasts.
If directed broadcast is enabled for an interface, incoming IP packets
whose addresses identify them as directed broadcasts intended for the
subnet to which that interface is attached will be exploded as
broadcasts on that subnet. If an access list has been configured with
the ip directed-broadcast command, only directed broadcasts that are
permitted by the access list in question will be forwarded; all other
directed broadcasts destined for the interface subnet will be dropped.
"
IMO, the command need to be configured on the receiving end...
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Anthony Bonilla
Sent: Thursday, February 22, 2007 9:21 PM
To: Schulz, Dave
Cc: ccielab@groupstudy.com
Subject: Re: Helper address and directed broadcast Question
Okay, I think I got it - thanks a lot for your help.
On 2/22/07, Schulz, Dave <DSchulz@dpsciences.com> wrote:
>
> No, the helper addresses will allow you to direct broadcasts for say,
> DHCP. Pixie, etc for startup. The directed broadcast would relate to
> allowing directed broadcast out od the interface. Afaik, as it was
> explained to me.. Hope this helps.
>
> Dave Schulz
> *** Sent from my Blackberry ***
>
> -----Original Message-----
> From: Anthony Bonilla <anthonybonilla.ccie@gmail.com>
> To: Schulz, Dave
> CC: ccielab@groupstudy.com <ccielab@groupstudy.com>
> Sent: Wed Feb 21 22:40:32 2007
> Subject: Re: Helper address and directed broadcast Question
>
> Dave,
>
> Thanks for your response - I was beginning to think that my messages
were
> not making it to the GS but now I feel a lot better after you replied.
>
> In any event, just to make sure that I got it: if you look at my
depiction
> of the setup, if we were asked to enable HSRP on the LAN interface of
Router
> R1 and use LAN broadcast address between Routers R3 and R4. In that
case,
> are you saying that I should enable helper address on the LAN
interfaces of
> both R1 and R4 and don't need to enable directed broadcast on either
of the
> interfaces (I thought that I had to have directed-broadcast enabled on
R4's
> LAN interface and would only enable helper address on R1's LAN
interface so
> that the traffic is directed towards the LAN segment between R and
R4)? Pls
> elaborate a bit, if at all possible. Thanks again for taking the time
to
> respond.
>
> Tony
>
>
> On 2/21/07, Schulz, Dave <DSchulz@dpsciences.com> wrote:
>
> Anthony -
>
> You will want to enable the ip helper on both routers that are
> acting as
> the hsrp group. The ip helper will provide the directed
> broadcast.
> HTH.
>
>
> Dave Schulz,
> Email: dschulz@dpsciences.com
>
>
>
> -----Original Message-----
> From: nobody@groupstudy.com
<mailto:nobody@groupstudy.com<nobody@groupstudy.com>>
> [mailto:nobody@groupstudy.com <nobody@groupstudy.com>] On Behalf Of
> Anthony Bonilla
> Sent: Wednesday, February 21, 2007 9:12 PM
> To: ccielab@groupstudy.com
<mailto:ccielab@groupstudy.com<ccielab@groupstudy.com>
> >
> Subject: Re: Helper address and directed broadcast Question
>
> Any takers? Can someone pls answer the following question
because
> I
> have
> tried searching archives but hasn't been able to find a
definitive
> answer as
> yet? Would appreciate someone's help with this.
>
> Thx.
>
>
> On 2/19/07, Anthony Bonilla <anthonybonilla.ccie@gmail.com>
wrote:
> >
> > Hello GS,
> >
> > First of all, I would like to apologize for asking this
basic
> (for
> some on
> > this group) question but I have this doubt in my mind for
some
> time
> now and
> > wanted to see if someone from this group can help me
understand
> this
> > concept. If we enable HSRP on a router for users connected
to
> one of
> it's
> > LAN interfaces (LAN interface of router R1 in the below
> presentation)
> and
> > then use broadcast address of another router's LAN segment
(say,
> LAN
> > interface between R3 and R4) as the address for IP HELPER
> ADDRESS
> command,
> > where would I need to worry about enabling directed
broadcast?
> >
> > LAN --- R1 --- Serial --- R2 --- Serial --- R3 ---- LAN ----
R4
> >
> > Also, if someone would be kind enough to let me know if I
need
> to
> enable
> > broadcast support at all if the helper address is, let's
say,
> R4's
> > LAN interface address?
> >
> > I look forward to your response to this question.
> >
> > TIA,
> >
> > Tony.
>
>
>
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