Re: multicast helper map and ip directed-broadcast

You would think so, put 2 routers on the same ethernet segment.

R1>F0/0----------F0/0<R2

1.1.1.1------------------1.1.1.2

ping 1.1.1.255 from either and do debug ip packet detail.

you only see 255.255.255.255, maybe IOS is converting

On Tue, Oct 12, 2010 at 12:07 PM, Jack Router <pan.router_at_gmail.com> wrote:

> Ip directed-broadcast is configured on R4, F0/0 and "debug ip udp" shows
> the
> following:
>
>
>
> R5:
>
> *Mar 1 12:16:07.528: UDP: rcvd src=10.1.12.1(520),
> dst=255.255.255.255(520), length=32
>
>
>
> R4:
>
> *Mar 1 12:18:33.744: UDP: rcvd src=10.1.12.1(520), dst=224.1.1.1(520),
> length=32
>
> *Mar 1 12:18:33.748: UDP: forwarded broadcast 520 from 10.1.12.1 to
> 255.255.255.255 on FastEthernet0/0
>
>
>
> No directed broadcast in this output. However R4 needs to be configured
> with
> "ip directed-broadcast" without it R5 will not receive anything. Now I am
> really confused...
>
> Do I understand correctly that I should see "dst=10.1.45.255" in debug ?
>
>
>
>
>
> From: Narbik Kocharians [mailto:narbikk_at_gmail.com]
> Sent: 12-Oct-10 11:07
> To: Jack Router
> Subject: Re: multicast helper map and ip directed-broadcast
>
>
>
> Because the last router takes the Mcast traffic and converts it and sends
> it
> as a directed broadcast, and we know that Cisco routers do not allow
> directed broadcast unless specifically configured.
>
> On Tue, Oct 12, 2010 at 7:23 AM, Jack Router <pan.router_at_gmail.com> wrote:
>
> Hello Experts,
>
> I have a question regarding directed broadcast in multicast helper map: Why
> "ip directed-broadcast" is needed on R4 int F0/0? It does not work without
> it.
> For those who use Narbik workbooks it is about Vol2, Multicast, Lab 10.
>
> Topology:
>
> R1(F0/0)---(F0/0)R2--frame--R3--frame--R4(F0/0)---(F0/0)R5
>
> Multicast runs on R2, R3, R4
> R1 is configured to send broadcast updates.
>
> When I debug ip packets on R5 I see that R5 receives RIP updates from R1
> with destination address of 255.255.255.255. There is no 10.1.45.255 in the
> debug:
>
> *Mar 1 10:31:30.717: IP: s=10.1.12.1 (FastEthernet0/0), d=255.255.255.255,
> len 52, rcvd 2
>
> Why then ip directed-broadcast is needed in R4 F0/0 ? What it does ?
>
> Thanks,
>
>
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> Narbik Kocharians
> CCSI#30832, CCIE# 12410 (R&S, SP, Security)
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Received on Tue Oct 12 2010 - 12:45:18 ART