Re: How to get rif of DHCP broadcast logging?

  • From: "Jim Harrison" <jim@xxxxxxxxxxxx>
  • To: "[ISAserver.org Discussion List]" <isalist@xxxxxxxxxxxxx>
  • Date: Sun, 6 Jan 2002 11:51:05 -0800

That's all true, but what does directed DNS traffic have to do with
broadcast DHCP traffic?
My point is :
    1. The majority of DHCP traffic is broadcast-based, since the DHCP
client won't have an IP address
    2. ISA blocks and logs all broadcast traffic on any external interface
(including DMZ interfaces)
    3. Any attempt to specify a broadcast IP in the local computer part of
the packet filter will cause the Firewall service to choke on the PF
definition.
Essentially, you can't stop ISA from logging broadcast traffic on the
external interface.

Jim Harrison
MCP(NT4, W2K), A+, Network+, PCG
http://isaserver.org/authors/harrison/
Read the books!

----- Original Message -----
From: "David Elmquist" <david@xxxxxxxxxx>
To: "[ISAserver.org Discussion List]" <isalist@xxxxxxxxxxxxx>
Sent: Sunday, January 06, 2002 11:35
Subject: [isalist] Re: How to get rif of DHCP broadcast logging?


http://www.ISAserver.org



Just for fun, i`ve tried it out.
Since I haven`t got any DHCP servers on the outside of my ISA,
I used a router to generate DNS broadcasts which look like this:

Router_IP 255.255.255.255 Udp 57125 53 - BLOCKED
ISA_IP

I then constructed a packet filter with the following properties:

Block
UDP
Direction: Receive only
Local port: fixed - 53
Remote port - all ports

Local computer: This ISA server`S External address: 0.0.0.0
Remote computer: Router_IP

When I untick "Log any packets mathing this filter", I do not get the
Broadcast traffic in my log.

 David Elmquist


-----Original Message-----
From: Jim Harrison [mailto:jim@xxxxxxxxxxxx]
Sent: 6. januar 2002 20:20
To: [ISAserver.org Discussion List]
Subject: [isalist] Re: How to get rif of DHCP broadcast logging?

http://www.ISAserver.org


You can't specify "255.255.255.255." (broadcast address) in the packet
filter properties for the ISA IP, which is what ISA is blocking.

Jim Harrison
MCP(NT4, W2K), A+, Network+, PCG
http://isaserver.org/authors/harrison/
Read the books!

----- Original Message -----
From: "David Elmquist" <david@xxxxxxxxxx>
To: "[ISAserver.org Discussion List]" <isalist@xxxxxxxxxxxxx>
Sent: Sunday, January 06, 2002 10:43
Subject: [isalist] Re: How to get rif of DHCP broadcast logging?


http://www.ISAserver.org




I would have thought, one could construct a packet filter along
The lines of this:

Block
UDP
Local port: - fixed port 68 - direction: Receive
Remote port: - fixed port 67 -
And then untick "log any packets matching this filter.

Haven`t tried it, though.

I did once construct a packet filter to accept DHCP broadcast from
external source. Had to use 0.0.0.0 as "This ISA server`s external
address" to get it
To work. It might be applicable in the above example too.

 David Elmquist


-----Original Message-----
From: Jim Harrison [mailto:jim@xxxxxxxxxxxx]
Sent: 6. januar 2002 19:26
To: [ISAserver.org Discussion List]
Subject: [isalist] Re: How to get rif of DHCP broadcast logging?

http://www.ISAserver.org


No; ISA logs all blocked traffic, regardless of its origin.

Jim Harrison
MCP(NT4, W2K), A+, Network+, PCG
http://isaserver.org/authors/harrison/
Read the books!

----- Original Message -----
From: "Leo" <leo@xxxxxxxxxx>
To: "[ISAserver.org Discussion List]" <isalist@xxxxxxxxxxxxx>
Sent: Sunday, January 06, 2002 04:10
Subject: [isalist] How to get rif of DHCP broadcast logging?


http://www.ISAserver.org


I'm running a DHCP server on the ISA Server. The external adapter get's
it's address from an external DHCP server (at my ISP).
I notice lots of blocked UDP packets (port 67, 68) if I check the
loggings
on the ISA server. They are comming from my internal adapter.

I want to prevent these broadcasts to my external adapter because they
are
flooding my logfile.

Is there a way to do this??

Thanks,
Leo

2002-01-06 00:00:15 192.168.255.1 255.255.255.255 Udp 68 67
BLOCKED 62.45.59.38
2002-01-06 00:00:15 192.168.255.1 255.255.255.255 Udp 67 68
BLOCKED 62.45.59.38
2002-01-06 00:00:23 192.168.255.1 255.255.255.255 Udp 68 67
BLOCKED 62.45.59.38
2002-01-06 00:00:23 192.168.255.1 255.255.255.255 Udp 67 68
BLOCKED 62.45.59.38
2002-01-06 00:00:31 192.168.255.1 255.255.255.255 Udp 68 67
BLOCKED 62.45.59.38
2002-01-06 00:00:31 192.168.255.1 255.255.255.255 Udp 67 68
BLOCKED 62.45.59.38

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