From: Oliver Ziltener (ziltener@netcloud.ch)
Date: Thu Sep 04 2003 - 17:41:30 GMT-3
Hello Brian
excellent work! Actually I saw this stuff in a config of a customer and was
wondering how this work-and it really works for a software distribution tool!
I usually used the helper-address only with host entries in the past.
You see, even a ccie is still learing....
thanks for the feedback
Oliver
-----Urspr|ngliche Nachricht-----
Von: Brian McGahan [mailto:bmcgahan@internetworkexpert.com]
Gesendet: Donnerstag, 4. September 2003 19:18
An: Oliver Ziltener; ccielab@groupstudy.com
Betreff: RE: ip helper-address to a network instead to a single host
Oliver,
No, it will not drop the request off as a directed broadcast.
If the helper address is connected to a local interface, however, the
router will send a generic broadcast out that interface. Take the
following case:
R1--E0/0-12.0.0.0/8-E0/0--R2--S0/1-23.0.0.0/8-S1/3--R3
R1 is requesting an address through DHCP. R2 is forwarding requests to
23.0.0.0. R3 is running DHCP. Here is the debug output on R2:
IP: s=0.0.0.0 (Ethernet0/0), d=255.255.255.255, len 604, rcvd 2
UDP src=68, dst=67 <----DHCP request heard from R1
IP: s=12.0.0.2 (local), d=255.255.255.255 (Serial0/1), len 604, sending
broad/multicast
UDP src=67, dst=67 <----DHCP request forwarded to 23.0.0.0 via
generic broadcast
IP: s=23.0.0.3 (Serial0/1), d=12.0.0.2, len 328, rcvd 4
UDP src=67, dst=67 <----DHCP server responds with unicast reply
IP: s=12.0.0.2 (local), d=255.255.255.255 (Ethernet0/0), len 328,
sending broad/multicast
UDP src=67, dst=68 <----R2 broadcasts reply out to E0/0 to R1
You *could* theoretically use broadcast/multicast conversion (ip
multicast helper-map) to accept the broadcast, send it over a multicast
domain, and drop it off as a directed broadcast.
Is there something you are specifically trying to accomplish?
HTH,
Brian McGahan, CCIE #8593
bmcgahan@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
Toll Free: 877-334-8987
Direct: 708-362-1418 (Outside the US and Canada)
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Oliver Ziltener
Sent: Thursday, September 04, 2003 3:00 AM
To: ccielab@groupstudy.com
Cc: Oliver Ziltener
Subject: ip helper-address to a network instead to a single host
Hello all
only for clarification...
when i have the cmd ip helper-address 192.168.100.0 (note this is a
network
instead as usually used for a single host entry)
will then the last router with the interface into network 192.168.100.0
do a
local broadcast (192.168.100.255)?
thanks for feedback
Oliver
This archive was generated by hypermail 2.1.4 : Wed Oct 01 2003 - 07:24:23 GMT-3