From: ccie2be (ccie2be@nyc.rr.com)
Date: Fri Nov 05 2004 - 20:05:10 GMT-3
Andy,
According to Brain McGahan, we're barking up the wrong tree.
As you can see, I'm still trying to fit all the pieces together but I'm sure
I don't have the complete picture or some of the info I'm hearing isn't 100%
correct. It's always hard to know.
Anyway, contrary to what I described before, Brain tells me that, in fact,
R4 is a dhcp client and negotiate it's ip address via ppp's ipcp.
Maybe it's terminology, but here's the problem I'm having with this.
If R4 is, in fact, a dhcp client, then once the link comes up, shouldn't R4
send to R5 a dhcp discover message?
Looking again at the debug dhcp output from R5, the lnk is up, but there's
no dhcp discover message.
********************************************
For those of you just joining this thread, here's the basic setup.
R4 --- isdn ---- R5 ----- R1
R4's dialer int is configured with encap ppp and ip address negotiated.
R5's dialer int is configured with encap ppp and peer default ip address
dhcp and the global command, ip dhcp-server <ip addr>.
R1 is the dhcp server. It's connected to R5 directly via f/r.
At this point, no routing is configured, so after R1 gets a dhcp request, it
wouldn't know how to respond as it doesn't know about the subnet connecting
R4 and R5 over the isdn link.
************************************************
The problem is that once the isdn link comes up, R4 never gets an ip address
assigned to it's dialer interface. Now, even though R1 without routing
configured, can't respond to a dhcp request, it should still recieve the
requests. However, a debug dhcp on R1 shows that R1 never recieves a dhcp
request.
I'm trying to figure why and where in the process things are going wrong.
If you scroll down to the first post of this thread, you can see the debug
dhcp output from R5 after the link comes. Notice, there's no indication
that R5 is gettting a dhcp request from R4.
If what Brain says about R4 being a dhcp client is really true, shouldn't we
see in R5's debug dhcp output, a dhcp request from R4?
Let me know what you think.
Thanks, Tim
----- Original Message -----
From: "Edwards, Andrew M" <andrew.m.edwards@boeing.com>
To: "ccie2be" <ccie2be@nyc.rr.com>; <ccielab@groupstudy.com>
Sent: Friday, November 05, 2004 4:13 PM
Subject: RE: dhcp and address negotiation over an isdn link
Well, I guess its kind of caveat emptor...
But, I think between the two of us we've nailed this one.
With R4 being negotiate, R5 has to be setup for both ip dhcp-server and
ip dhcp-proxy.
If R4 were an ip add dhcp-client though... R5 would need helper-address.
Of course, its blind leading the blind here... But I do know a bit about
DHCP. 8)
-----Original Message-----
From: ccie2be [mailto:ccie2be@nyc.rr.com]
Sent: Friday, November 05, 2004 12:16 PM
To: Edwards, Andrew M; ccielab@groupstudy.com
Subject: Re: dhcp and address negotiation over an isdn link
Hi Andrew,
I was thinking about what you said below about using the command, ip
address-pool dhcp-proxy-client. And, it made me wonder if I was
thinking about this all wrong.
Initially, I was thinking that once the link between R4 and R5 came up,
R4 because it has ip address negotiated configured on it becomes a dhcp
client and therefore would send out a dhcp request.
But, maybe this is wrong because R4 is connecting to R5 via PPP and
using PPP to negotiate an ip address. In other words, R4 isn't a really
dhcp client so it doesn't send out a dhcp request for an address.
But, now, looking at R5's configuration. It has the interface command,
peer default ip address dhcp, on it's Dialer interface which means it
should use dhcp to get and assign an ip address to R4 when it gets a
dhcp request from R4. But, because R4 isn't really (or rather R4
doesn't consider itself) a dhcp client, R4 never sends a dhcp request.
Therefore, for R5 to get an ip address for R4, it must send a dhcp
request on R4's behalf to the dhcp server and that's why the global
command, ip address-pool dhcp-proxy-client, is needed.
Realize that I'm completely making this up, but it seems plausible. Am
I getting warm?
Thanks, Tim
----- Original Message -----
From: "Edwards, Andrew M" <andrew.m.edwards@boeing.com>
To: "ccie2be" <ccie2be@nyc.rr.com>; <ccielab@groupstudy.com>
Sent: Friday, November 05, 2004 1:54 PM
Subject: RE: IEWB lab 13 dhcp & isdn task 4.3 and task 12.1
My thoughts....
On R5, you need ip helper-address to R1.
R5 is connecting to R4 on the callback but the DHCP lease is not being
negotiated. R5 see's the R4 request but it can't do anything with it...
So, get R5 to encapsulate (unicast) and forward the local link broadcast
from R4 for a DHCP Lease Request. Once you see NCP on the BRI link
negotiate the Network Control Protocol address received from R1 you will
get connectivity at layer 3 between r4 and r5.
Alternatively, if you want to specify the IP address of the DHCP server,
you will need to use the global ip address-pool dhcp-proxy-client
command to specify that R5 should proxy DHCP requests on behalf of
locally connected clients. Two ways to do the same thing.... One being
more efficient (I think the later).
HTH,
andy
-----Original Message-----
From: ccie2be [mailto:ccie2be@nyc.rr.com]
Sent: Friday, November 05, 2004 6:57 AM
To: Group Study
Subject: Fw: IEWB lab 13 dhcp & isdn task 4.3 and task 12.1
Hey guys,
In the isdn portion of this task, I needed to configure dialer profiles
on both R4 and R5, have R5 call R4 and then make R4 hangup and callback
R5. I got this part to work. To confirm that this was working I used,
isdn test call int bri 0/0 5272034 and enabled debug dialer on R4. When
I reviewed the debug logs, I could see the call from R5 connect, then
disconnect and then R4 callback R5.
However, I also needed to configure R4 to get it's dialer's interface ip
address from a dhcp server directly connected to R5.
I also enabled debug dhcp on R4 and R5, but I can't tell from the debug
out what's really going on. So, I don't know if R4 ever really got an ip
address.
I've configured R4 and R5 as shown is the SG, but the dhcp part doesn't
seem to working, although I'm not 100% sure. Once the link was up after
R4 called back R5, I did several pings but those never were successful.
I was struggling with this for hours but never got pings to work across
the isdn link, so I'm hoping someone can help me understand what's going
on.
Here's some output from deb dhcp on R5:
*Mar 1 07:08:42.478: DHCP Lease server: 0.0.0.0, state: 1 Selecting
*Mar 1 07:08:42.478: DHCP transaction id: FCC10C
*Mar 1 07:08:42.478: Lease: 0 secs, Renewal: 0 secs, Rebind: 0
secs
*Mar 1 07:08:42.478: Next timer fires after: 00:00:03
*Mar 1 07:08:42.478: Retry count: 2 Client-ID:
cisco-139.3.45.5-BRI0/0:1
*Mar 1 07:08:42.478: DHCP: SDiscover: sending 285 byte length DHCP
packet *Mar 1 07:08:42.478: DHCP: SDiscover 285 bytes *Mar 1
07:08:53.078: DHCP: QScan: Purging entry *Mar 1 07:08:53.078: DHCP:
deleting entry 622AE8CC 0.0.0.0 from list *Mar 1 07:08:53.078: Temp IP
addr: 0.0.0.0 for peer on Interface: unknown *Mar 1 07:08:53.078: Temp
sub net mask: 0.0.0.0
*Mar 1 07:08:53.078: DHCP Lease server: 0.0.0.0, state: 8 Purging
*Mar 1 07:08:53.078: DHCP transaction id: FCC107
*Mar 1 07:08:53.078: Lease: 0 secs, Renewal: 0 secs, Rebind: 0
secs
*Mar 1 07:08:53.078: No timer running
*Mar 1 07:08:53.078: Retry count: 0 Client-ID:
*Mar 1 07:08:57.178: DHCP: QScan: Purging entry
*Mar 1 07:08:57.178: DHCP: deleting entry 629D70C0 0.0.0.0 from list
*Mar 1 07:08:57.178: Temp IP addr: 0.0.0.0 for peer on Interface:
unknown *Mar 1 07:08:57.178: Temp sub net mask: 0.0.0.0
*Mar 1 07:08:57.178: DHCP Lease server: 0.0.0.0, state: 8 Purging
*Mar 1 07:08:57.178: DHCP transaction id: FCC108
*Mar 1 07:08:57.178: Lease: 0 secs, Renewal: 0 secs, Rebind: 0
secs
*Mar 1 07:08:57.178: No timer running
*Mar 1 07:08:57.178: Retry count: 0 Client-ID:
*Mar 1 07:09:01.278: DHCP: QScan: Purging entry
*Mar 1 07:09:01.278: DHCP: deleting entry 622AE168 0.0.0.0 from list
*Mar 1 07:09:01.278: Temp IP addr: 0.0.0.0 for peer on Interface:
unknown *Mar 1 07:09:01.278: Temp sub net mask: 0.0.0.0
*Mar 1 07:09:01.278: DHCP Lease server: 0.0.0.0, state: 8 Purging
*Mar 1 07:09:01.278: DHCP transaction id: FCC109
*Mar 1 07:09:01.278: Lease: 0 secs, Renewal: 0 secs, Rebind: 0
secs
*Mar 1 07:09:01.278: No timer running
*Mar 1 07:09:01.278: Retry count: 0 Client-ID:
*Mar 1 07:09:05.378: DHCP: QScan: Purging entry
*Mar 1 07:09:05.378: DHCP: deleting entry 622A94C8 0.0.0.0 from list
*Mar 1 07:09:05.378: Temp IP addr: 0.0.0.0 for peer on Interface:
unknown *Mar 1 07:09:05.378: Temp sub net mask: 0.0.0.0
*Mar 1 07:09:05.378: DHCP Lease server: 0.0.0.0, state: 8 Purging
*Mar 1 07:09:05.378: DHCP transaction id: FCC10A
*Mar 1 07:09:05.378: Lease: 0 secs, Renewal: 0 secs, Rebind: 0
secs
*Mar 1 07:09:05.378: No timer running
*Mar 1 07:09:05.378: No timer running
*Mar 1 07:09:09.478: DHCP: QScan: Purging entry
*Mar 1 07:09:09.478: DHCP: deleting entry 629D34B0 0.0.0.0 from list
*Mar 1 07:09:09.478: Temp IP addr: 0.0.0.0 for peer on Interface:
unknown *Mar 1 07:09:09.478: Temp sub net mask: 0.0.0.0
*Mar 1 07:09:09.478: DHCP Lease server: 0.0.0.0, state: 8 Purging
*Mar 1 07:09:09.478: DHCP transaction id: FCC10B
*Mar 1 07:09:09.478: Lease: 0 secs, Renewal: 0 secs, Rebind: 0
secs
*Mar 1 07:09:09.478: No timer running
*Mar 1 07:09:09.478: Retry count: 0 Client-ID:
*Mar 1 07:09:13.578: DHCP: QScan: Purging entry
*Mar 1 07:09:13.578: DHCP: deleting entry 629D3684 0.0.0.0 from list
*Mar 1 07:09:13.578: Temp IP addr: 0.0.0.0 for peer on Interface:
BRI0/0:1 *Mar 1 07:09:13.578: Temp sub net mask: 0.0.0.0
*Mar 1 07:09:13.578: DHCP Lease server: 0.0.0.0, state: 8 Purging
*Mar 1 07:09:13.578: DHCP transaction id: FCC10C
*Mar 1 07:09:13.578: Lease: 0 secs, Renewal: 0 secs, Rebind: 0
secs
*Mar 1 07:09:13.578: No timer running
*Mar 1 07:09:13.578: Retry count: 0 Client-ID:
cisco-139.3.45.5-BRI0/0:1
*Mar 1 07:10:18.866: %ISDN-6-DISCONNECT: Interface BRI0/0:1
disconnected from 5272034 , call lasted 120 seconds *Mar 1
07:10:18.918: %LINK-3-UPDOWN: Interface BRI0/0:1, changed state to down
*Mar 1 07:10:18.922: %DIALER-6-UNBIND: Interface BR0/0:1 unbound from
profile D i1
************************************************************************
*****
********************
I also did a deb dhcp on R1, the dhcp server, but got nothing at all.
Here's R4's config. R4 is the dhcp client and is suppose to get an ip
address assigned to it dialer interface.
interface Dialer1
ip address negotiated
encapsulation ppp
dialer pool 1
dialer string 5272035
dialer caller 5272035 callback
Here's R5's config:
ip dhcp-server 139.3.15.1
interface Dialer1
ip address 139.3.45.5 255.255.255.0
encapsulation ppp
dialer pool 1
dialer string 5272034
dialer-group 1
peer default ip address dhcp
Here's R1's config. R1 is the dhcp server.
ip dhcp excluded-address 139.3.45.5 139.3.45.255
ip dhcp excluded-address 139.3.45.0 139.3.45.3
!
ip dhcp pool FOR-R4
network 139.3.45.0 255.255.255.0
Here's the topology:
R4 --- isdn ---- R5 --- f/r --- R1
I'm not running any routing protocols, but R5 and R1 can ping each
other.
R5 can call R4. When it does, R4 takes the call, hangup, and calls R5
back. But, once the call is connected, R4 and R5 still can't ping each
other. A debug on R5 shows the pings are "unroutable". I don't know
why since, of course, R4 and R5 are directly connected via the isdn
link.
Can anybody help me understand what's going on here with dhcp and the
ping problem?
Thanks for any insight.
Tim
This archive was generated by hypermail 2.1.4 : Thu Dec 02 2004 - 06:57:39 GMT-3