RE: UDP flooding

From: James.Jackson@broadwing.com
Date: Mon Jun 23 2003 - 17:02:46 GMT-3

IRDP is not related to UDP flooding. It is simply a means of dynamically
assigning a route to the workstations via ICMP without having them run gated
and listening to RIP for instance i.e. it provides the redundancy for the
outbound unicast traffic. It does appear that IP is being routed (anything
else would be bridged) and that bridging in this case only serves to create
the spanning-tree and limit the UDP flooding. IGRP is providing the
redundancy beyond the first hop i.e. in steady state Router A is forwarding
the unicasts, if it loses its E1 interface, it could end up sending the
traffic out the same interface it came in on to Router B but would also
issue an ICMP Re-direct telling the workstation to use Router B next time.

HTH,
James

-----Original Message-----
From: wing_lam@jossynergy.com [mailto:wing_lam@jossynergy.com]
Sent: Monday, June 23, 2003 11:35 AM
To: Jackson, James (DS Engineering)
Cc: ccielab@groupstudy.com
Subject: RE: UDP flooding

Hi, James

Oh really? I see the example running IGRP and it configured IP addresses in
different interfaces so just I guess routing is activated.

But I cannot see it configure any IRB, have you got examples like that?

For the IRDP, is it a mandatory so that for the UDP flooding works?

Thx,
BBD (Big Black Dog)

 

                      James.Jackson@bro

                      adwing.com To:
wing_lam@jossynergy.com

                                               cc:
ccielab@groupstudy.com

                      06/24/2003 12:26 Subject: RE: UDP flooding

                      AM

 

 

It doesn't seem like much more than that...i.e. forcing the UDP broadcasts
to be forwarded down the spanning-tree and choosing the other router as
outbound gateway via IRDP. If you want to also route, I'd imagine you want
to run IRB.

-----Original Message-----
From: wing_lam@jossynergy.com [mailto:wing_lam@jossynergy.com]
Sent: Monday, June 23, 2003 11:03 AM
To: Jonathan V Hays
Cc: ccielab@groupstudy.com
Subject: RE: UDP flooding

Hi Johnathan,

Thx, I think the broadcast MAC will be with all 1's but I have no idea on
the OUI type with all ones, even after I searched the following link:

http://www.cisco.com/en/US/products/sw/iosswrel/ps1824/products_command_refe

rence_chapter09186a008008065d.html

So I guess the example is wrong, and if it's my fault please let me know.

But I still don't know how the "UDP flooding" works. In my perception, it
means "UDP broadcast packets passing hope by hope with the destination
broadcast address changes accordingly in each hope, and the spanning tree
will deal with the forwarding and blocking; while other normal user
traffics will still through unicast routing"

Am I right, anybody please correct me; I am still not very clear in how the
spanning-tree part of the "UDP flooding" functions.

Thx a lot,
BBD (Big Black Dog)

                      "Jonathan V Hays"

                      <jhays@jtan.com> To:
<wing_lam@jossynergy.com>

                      Sent by: cc:
<ccielab@groupstudy.com>

                      nobody@groupstudy Subject: RE: UDP flooding

                      .com

                      06/23/2003 11:11

                      PM

                      Please respond to

                      "Jonathan V Hays"

> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
> Behalf Of wing_lam@jossynergy.com
> Sent: Monday, June 23, 2003 10:22 AM
> To: Connie Nie
> Cc: ccielab@groupstudy.com
> Subject: RE: UDP flooding
>
>
> Also, what is the use of access-list 201 deny 0xffff 0x0000
> in example?

You are denying MAC addresses with OUI of all ones.

HINT: So what type of MAC address would begin with all ones?

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