From: Brian Dennis (bdennis@internetworkexpert.com)
Date: Thu Sep 25 2003 - 13:53:36 GMT-3
Scott,
Can you send the debugs from when CDP generates this host route in the
routing table and causes OSPF to trigger a call? Of course add the "no
peer neighbor-route" command so we can be sure it's CDP that is
generating the host route. Actually if you can get the "peer
neighbor-route" command to cause an OSPF demand circuit to trigger a
call without involving route redistribution send the debugs for that
also.
Are you 100% sure that the host route for the "peer neighbor-route"
command is generated by CDP or has anything to do with CDP? Disable CDP
and see if it still appears. In fact try it with another vendor's device
on the other side if you have one around.
The "peer neighbor-route" command is needed normally for unnumbered
links. If a link is unnumbered a route will be needed to the remote
side's IP address. This "peer neighbor-route" command is how a route to
the remote end is created. If you disable the "peer neighbor-route"
command on an unnumbered link, a static route will normally be needed to
reach the remote end.
For someone to get an understanding of the "peer neighbor-route" command
and how it's used in the real world I recommend enabling PPP on a serial
link between two routers. Use IP unnumbered off of each respective
router's loopback interface and then ping the remote end's loopback. Now
do a "no peer neighbor-route" command on each side of the link and
'bounce' (shut/no shut) the interface. Try to ping the remote end's
loopback to see the benefit of having the "peer neighbor-route" command
on.
In regards to the original question about CDP triggering a call, I would
be impressed if someone can create a dialer-list that permits CDP to
begin with. CDP triggering a call by default is an urban legend.
Brian Dennis, CCIE #2210 (R&S/ISP-Dial/Security)
bdennis@internetworkexpert.com
Toll Free: 877-224-8987
Direct: 775-745-6404 (Outside the US and Canada)
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Scott Morris
Sent: Thursday, September 25, 2003 8:39 AM
To: 'Barney Gaumer'; 'Nawaz, Ajaz'; 'Donny MATEO'; 'Peng Zheng'
Cc: ccielab@groupstudy.com; nobody@groupstudy.com
Subject: RE: Should I disable cdp on ISDN
Let's back up a little bit... Dialer circuits are interesting creatures
unto themselves.
CDP will allow the generation of a neighbor route (/32 host route). When
it comes up, it's in your OSPF table. When CDP neighbor goes away (no
relation to OSPF), then the host route goes away. If the host route
goes away, your database changes and OSPF will dial up the other side to
talk about it. Then the route comes back...
It's a big evil circle.
You can disable CDP. That's one way to solve the problem. The other
way is:
No peer neighbor-route
That will prevent the generation of the /32 route for the CDP neighbor
on a dial circuit. So from that aspect, I can see where people get the
idea that CDP brings the link up. It doesn't really, but because of
something 'assisted by' CDP that it does.
Give that a whirl and see whether your up/down/up/down problem goes
away!
Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713,
CISSP, JNCIS, et al.
IPExpert CCIE Program Manager
IPExpert Sr. Technical Instructor
swm@emanon.com/smorris@ipexpert.net
http://www.ipexpert.net
-----Original Message-----
From: Barney Gaumer [mailto:bagaumer@yahoo.com]
Sent: Thursday, September 25, 2003 11:27 AM
To: Scott Morris; 'Nawaz, Ajaz'; 'Donny MATEO'; 'Peng Zheng'
Cc: ccielab@groupstudy.com; nobody@groupstudy.com
Subject: RE: Should I disable cdp on ISDN
I was playing with OSPF demand circuit the other day &
the only way I could get everything to work was to
enable broadcast on the "dialer map ip" and use "ospf database-filter"
otherwise the link kept flapping up and down.
The adjacency occured like it should for a demand
circuit and all of the routes were there, just didn't
think I had to do anything more than make one side of
the ISDN circuit a demand circuit.
What did I do wrong??
interface BRI0/0
bandwidth 128
ip address 10.1.1.1 255.255.255.0
encapsulation ppp
ip ospf demand-circuit
ip ospf database-filter all out
dialer map ip 10.1.1.2 name rtr-g broadcast
4082222222
dialer load-threshold 1 outbound
dialer-group 1
isdn switch-type basic-ni
isdn spid1 40811111111
isdn spid2 40811111112
no cdp enable
ppp authentication chap
ppp chap hostname rtr-a
ppp chap password 0 cisco
ppp multilink
--- Scott Morris <swm@emanon.com> wrote:
> OSPF Demand Circuit has nothing to do with whether
> CDP will bring your
> circuit up or not! Your definition of interesting
> traffic defines that.
> OSPF demand circuit doesn't define interesting
> traffic. It makes sure
> that even though OSPF >IS< interesting traffic, it
> won't be constantly
> talking to the other side unless something change.
>
> OSPF Demand Circuit suppresses the hello packets
> (which would be
> interesting) and puts routes in the database into a
> do not age state in
> order to keep them happy. And keeps the neighbor
> connection formed
> (part of suppressing hellos).
>
> CDP is still a completely different beast.
>
>
> Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service
> Provider) #4713,
> CISSP, JNCIS, et al.
> IPExpert CCIE Program Manager
> IPExpert Sr. Technical Instructor swm@emanon.com/smorris@ipexpert.net
> http://www.ipexpert.net
>
>
> -----Original Message-----
> From: nobody@groupstudy.com
> [mailto:nobody@groupstudy.com] On Behalf Of
> Nawaz, Ajaz
> Sent: Thursday, September 25, 2003 8:58 AM
> To: 'Donny MATEO'; Peng Zheng
> Cc: ccielab@groupstudy.com; nobody@groupstudy.com
> Subject: RE: Should I disable cdp on ISDN
>
>
> as a reader this is the most complete reply.
> as I understand it, OPSF demand circuit is the only
> time where you would
> explicity disable cdp (interface only) in order to
> prevent an isdn
> circuit from coming UP unecessarily.
>
> ajaz
>
> -----Original Message-----
> From: Donny MATEO
> [mailto:donny.mateo@sg.ca-indosuez.com]
> Sent: 25 September 2003 08:57
> To: Peng Zheng
> Cc: ccielab@groupstudy.com; nobody@groupstudy.com
> Subject: Re: Should I disable cdp on ISDN
>
>
> What techology are you refering to ? It really is
> technology specific
>
> backup interface => no need
> static route => make sure you didn't define CDP as interesting traffic
> in
> the dialer-list (there is no need to turn it off)
> ospf demand-circuit => filter it out or turn it off
> dialer-watch=> no
> need i believe..not sure though..
>
> so which one is it are you refering to ?
>
> Donny
>
>
>
>
>
>
> Peng Zheng <zpnist@yahoo.com>
> Sent by: nobody@groupstudy.com
> 09/25/2003 03:24 PM
> Please respond to Peng Zheng
>
>
> To: ccielab@groupstudy.com
> cc: (bcc: Donny
> MATEO/ADPC/ASIA/BANQUE_INDOSUEZ/FR)
> Subject: Should I disable cdp on ISDN
>
>
> On page 144 CCIE Practical Studies: Security, it
> said
> cdp triggers the ISDN call and therefore should be
> disabled if it isn't needed.
>
> Is that true? SHould I always disable cdp when
> configure DDR on ISDN?
>
>
>
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This archive was generated by hypermail 2.1.4 : Wed Oct 01 2003 - 07:24:37 GMT-3