From: Brian McGahan (bmcgahan@internetworkexpert.com)
Date: Thu Dec 30 2004 - 14:06:10 GMT-3
Tim,
We just went over this exact issue just recently. Look at the
below posting.
HTH,
Brian McGahan, CCIE #8593
bmcgahan@internetworkexpert.com
Internetwork Expert, Inc.
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-----Original Message-----
From: Brian McGahan
Sent: Friday, November 05, 2004 5:25 PM
To: 'ccie2be'; 'Edwards, Andrew M'; 'ccielab@groupstudy.com'
Subject: RE: dhcp and address negotiation over an isdn link
Tim,
The output is there, you're just looking at the wrong debug.
You should be looking at the PPP negotiation, as seen in my previous
post.
The below is from R5's perspective, the DHCP client
*Mar 1 21:13:16.034: BR0/0:1 IPCP: O CONFREQ [Closed] id 1 len 10
*Mar 1 21:13:16.038: BR0/0:1 IPCP: Address 0.0.0.0 (0x030600000000)
R5 to R4: I have no address, please give me one
*Mar 1 21:13:16.050: BR0/0:1 IPCP: I CONFNAK [ACKsent] id 1 len 10
*Mar 1 21:13:16.050: BR0/0:1 IPCP: Address 45.0.0.5 (0x03062D000005)
R4 to R5: How about 45.0.0.5?
*Mar 1 21:13:16.050: BR0/0:1 IPCP: O CONFREQ [ACKsent] id 2 len 10
*Mar 1 21:13:16.054: BR0/0:1 IPCP: Address 45.0.0.5 (0x03062D000005)
R5 to R4: Mmmm.... okay
*Mar 1 21:13:16.062: BR0/0:1 IPCP: I CONFACK [ACKsent] id 2 len 10
*Mar 1 21:13:16.062: BR0/0:1 IPCP: Address 45.0.0.5 (0x03062D000005)
R4 to R5: It's all yours
*Mar 1 21:13:16.062: BR0/0:1 IPCP: State is Open
*Mar 1 21:13:16.066: BR0/0 IPCP: Install negotiated IP interface
address 45.0.0.5
R5: 45.0.0.5 is my address now
HTH,
Brian McGahan, CCIE #8593
bmcgahan@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
Toll Free: 877-224-8987 x 705
Outside US: 775-826-4344 x 705
24/7 Support: http://forum.internetworkexpert.com
Live Chat: http://www.internetworkexpert.com/chat/
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> ccie2be
> Sent: Friday, November 05, 2004 5:05 PM
> To: Edwards, Andrew M; ccielab@groupstudy.com
> Subject: Re: dhcp and address negotiation over an isdn link
>
> 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
>
>
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