Sign in with
Sign up | Sign in
Your question

IpTraffic encloded in EthBroadcasts should be routed

Last response: in Networking
Share
Anonymous
September 2, 2005 8:43:10 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Hello

i have full correct IpTraffic inside a Ethernet Frame.
The Eth Dest Mac is FFFF:FFFF:FFFF The Source MAc is correct.

Is it possible to configure a router to route this packages?

Immo
Anonymous
September 3, 2005 1:11:50 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

iwetzel@gmx.net wrote:

> Hello
>
> i have full correct IpTraffic inside a Ethernet Frame.
> The Eth Dest Mac is FFFF:FFFF:FFFF The Source MAc is correct.
>
> Is it possible to configure a router to route this packages?

Routers do not normally pass broadcast packets.
Anonymous
September 3, 2005 4:26:42 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

iwetzel@gmx.net wrote:
> i have full correct IpTraffic inside a Ethernet Frame.
> The Eth Dest Mac is FFFF:FFFF:FFFF The Source MAc is correct.

What do you mean by "full correct IpTraffic?" IIRC, unicast IP is not
supposed to be carried in a broadcast frame. Also, IIRC, IP routers
are not supposed to forward IP datagrams carried in broadcast frames.

So, what sort of IP traffic do you have being carried in a broadcast
frame?

rick jones
--
Wisdom Teeth are impacted, people are affected by the effects of events.
these opinions are mine, all mine; HP might not want them anyway... :) 
feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH...
Related resources
Anonymous
September 3, 2005 6:05:15 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Hello,

its unicast IP. The Sender doenst know the gateway IP and also not the
Gateway mac. Thats the reason why Its an broadcast. But its save that
the connection between sender and Gateway is an P2P Connection.

But may be there is an Ethernet Broadcast frame which on triggers the
Gateway to say something. Because if I recieve a frame from the gateway
I know his MAC due to the P2P connection. Due you know some kind of
ethernet broadcast which triggers a normal Router to send an answer?

Thanks a lot
Immo

Rick Jones schrieb:

> iwetzel@gmx.net wrote:
> > i have full correct IpTraffic inside a Ethernet Frame.
> > The Eth Dest Mac is FFFF:FFFF:FFFF The Source MAc is correct.
>
> What do you mean by "full correct IpTraffic?" IIRC, unicast IP is not
> supposed to be carried in a broadcast frame. Also, IIRC, IP routers
> are not supposed to forward IP datagrams carried in broadcast frames.
>
> So, what sort of IP traffic do you have being carried in a broadcast
> frame?
>
> rick jones
> --
> Wisdom Teeth are impacted, people are affected by the effects of events.
> these opinions are mine, all mine; HP might not want them anyway... :) 
> feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH...
Anonymous
September 3, 2005 6:06:08 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

But can I change this behavior ? Espacially for Extreme Networks Summit
L3Switches ?
Anonymous
September 3, 2005 11:50:58 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

iwetzel@gmx.net wrote:

> But can I change this behavior ? Espacially for Extreme Networks Summit
> L3Switches ?

Perhaps a better solution would be to find out why you're trying to do
something that goes against common practice. What is it that you're trying
to do, that requires a broadcast to go through a router. Incidentally,
routers are configured to avoid passing broadcasts, to limit how far
they'll travel, in order to avoid polluting the Internet with a lot of
useless garbage.
Anonymous
September 3, 2005 6:16:13 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

In article <1125738314.989817.164200@o13g2000cwo.googlegroups.com>,
<iwetzel@gmx.net> wrote:
:its unicast IP. The Sender doenst know the gateway IP and also not the
:Gateway mac. Thats the reason why Its an broadcast. But its save that
:the connection between sender and Gateway is an P2P Connection.

You mean something like ICMP Router Discovery, RFC1256?
http://www.faqs.org/rfcs/rfc1256.html


:But may be there is an Ethernet Broadcast frame which on triggers the
:Gateway to say something. Because if I recieve a frame from the gateway
:I know his MAC due to the P2P connection. Due you know some kind of
:ethernet broadcast which triggers a normal Router to send an answer?

In another message in the thread, you mentioned a very specific
kind of router and asked how it might be configured for forwarding.
If you have that level of control, then you could configure the
router to send out RIPv1 or RIPv2 packets announcing the default
route. Hearing such a route would tell you where the router was.


:But may be there is an Ethernet Broadcast frame which on triggers the
:Gateway to say something. Because if I recieve a frame from the gateway
:I know his MAC due to the P2P connection. Due you know some kind of
:ethernet broadcast which triggers a normal Router to send an answer?

Let's have another look at that. You are trying to find out the
IP address of the "gateway" and you propose to do that by
provoking the "router". But if one examines the context of your
request, then the "gateway" is -not- the same as the "router".

If the P2P traffic knows the remote IP address, then all it
has to do is unicast to that IP: all details about the path
it takes to get there will be handled by the IP stack, and you
don't need to worry about router MACs and so on... not unless you
are programming the IP stack itself.

If the P2P traffic does -not- know the remote IP address, then
it is not going to be able to get traffic to the remote endpoint
by sending a unicast traffic to the router's IP + MAC: the
router itself would end up processing the traffic, since the router
would see it's own IP. "normal" routers would drop such traffic
unless it happened to be management traffic (e.g., SNMP or ssh
to the router), or NTP, or unless the router was configured for
"small services" such as chargen.

Thus in the context of your messages, the "gateway" that you
are trying to provoke must be a device that actively participates
in the P2P transaction (even if only in "call setup".) If that
active device is beyond a router, then learning the MAC of
that active device wouldn't help you because you need the router's
MAC to send to, not the active device's MAC.


If you have enough control over the context that you can specify
switch models end to end, then there are three technologies
that I suggest you investigate: multicast, DHCP, and bootp
{DHCP is actually a kind of bootp, but your research will be
easier if you treat them as nearly two different protocols.)
--
"[...] it's all part of one's right to be publicly stupid." -- Dave Smey
Anonymous
September 4, 2005 10:25:32 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

What about configuring the router for proxy arp? Then add a host route on
the client that tells it that the other side of the P2P connection is local,
i.e. give it a zero metric and specify the gateway as the local IP address.
That should force it to arp the remote IP which the router can then answer.




"James Knott" <james.knott@rogers.com> wrote in message
news:roOdnaieF8PLZYXeRVn-rQ@rogers.com...
> iwetzel@gmx.net wrote:
>
>> Hello
>>
>> i have full correct IpTraffic inside a Ethernet Frame.
>> The Eth Dest Mac is FFFF:FFFF:FFFF The Source MAc is correct.
>>
>> Is it possible to configure a router to route this packages?
>
> Routers do not normally pass broadcast packets.
>
Anonymous
September 4, 2005 8:07:13 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

It is my impression (And I may be wrong...) That the normal behavior
for IP traffic is to use ARP on a broadcast when the local stack does
not know the MAC for the IP Address. The Router should respond with
his MAC as an answer to Route the packets. From there, the end station
knows to forward the packet using the Routers MAC.

I think that doing Unicast IP inside of an Ethernet Bcast is bad ...
Anonymous
September 4, 2005 8:21:58 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

iwetzel@gmx.net wrote:
> Hello,
>
> its unicast IP. The Sender doenst know the gateway IP and also not the
> Gateway mac. Thats the reason why Its an broadcast. But its save that
> the connection between sender and Gateway is an P2P Connection.
>
> But may be there is an Ethernet Broadcast frame which on triggers the
> Gateway to say something. Because if I recieve a frame from the gateway
> I know his MAC due to the P2P connection. Due you know some kind of
> ethernet broadcast which triggers a normal Router to send an answer?

What you describe here is not an unusual state of affirs. Unicast has
to go out to another IP subnet. Sender doesn't know the IP address of
the router, which means also doesn't know the MAC address.

One solution is for the sending host to monitor for RIP frames, to find
the router that way. Another is to use ICMP router discovery (RFC
1256).

Once the sending host has the IP address of the router, it proceeds
with ARP to find the MAC address, and sends the frame to that MAC
address.

Routers rarely forward frames with broadcast addresses. One of the few
times is when doing BOOTP or DHCP to a remote DHCP server (a server
that isn't co-located with the router).

Bert
Anonymous
September 5, 2005 4:03:07 AM

Archived from groups: comp.dcom.lans.ethernet (More info?)

Dougie! wrote:
> It is my impression (And I may be wrong...) That the normal behavior
> for IP traffic is to use ARP on a broadcast when the local stack does
> not know the MAC for the IP Address. The Router should respond with
> his MAC as an answer to Route the packets. From there, the end station
> knows to forward the packet using the Routers MAC.
>
> I think that doing Unicast IP inside of an Ethernet Bcast is bad ...

Your right. But for a arp you have to know the IP Address of the
router.
Anonymous
September 5, 2005 7:43:28 PM

Archived from groups: comp.dcom.lans.ethernet (More info?)

In article <1125903787.714375.104380@o13g2000cwo.googlegroups.com>,
<iwetzel@gmx.net> wrote:
:Your right. But for a arp you have to know the IP Address of the
:router.

Not if the router is doing proxy-arp, which is the case for most
routers that are handling a default route.
--
Daylight is a trademark of OSRAM SYLVANIA INC.
!