From: William Lijewski (ccie8642@hotmail.com)
Date: Thu Sep 25 2003 - 13:39:56 GMT-3
Something else to keep in mind, whatever is specified in the dialer-list as
interesting traffic will reset the 'dialer idle-timeout' as it traverses the
ISDN link. If the traffic going across the link isn't specified in the
dialer-list, it will not be considered interesting traffic and therefor will
not reset the 'dialer idle-timout'. So if CDP isn't listed in the
dialer-list as interesting traffic it will still be allowed to traverse the
ISDN, but it will not reset the idle-timeout, since it doesn't reset the
idle-timeout it won't keep the link up.
One easy way to see what I mean is to configure OSPF across the ISDN link.
For the dialer-list on both sides deny OSPF as interesting traffic, but
permit all other IP traffic.
dialer list 1 permit ip list 100
access-list 100 deny ospf any any
access-list 100 permit ip any any
Then ping across the ISDN link. It will should come up, and OSPF should
neighbor up like normal. Then after 120 seconds (give or take) the line
will go down. OSPF will not be considered interesting traffic, even though
its continually going across the line, and it will not reset the
idle-timeout. You can use the debug dialer command to see what it
consideres interesting traffic.
Bill Lijewski
CCIE #8642
Network Learning Inc
5 Day R&S CCIE Bootcamp Instructor
>From: "ccie2be" <ccie2be@nyc.rr.com>
>Reply-To: "ccie2be" <ccie2be@nyc.rr.com>
>To: "Group Study" <ccielab@groupstudy.com>, "Jonathan V Hays"
><jhays@jtan.com>
>Subject: Re: Should I disable cdp on ISDN
>Date: Thu, 25 Sep 2003 11:44:37 -0400
>
>Hi all,
>
>While I can't claim to be 100% positive about what I'm about to say, I
>think
>my previous statements remain correct. To reiterate, there are 2 issues
>a)
>what trigger call and b) what traffic transits the link once it's UP.
>
>With Backup Interface, the primary interface going down triggers call.
>With Dialer Watch, the the absense of a watched route triggers call.
>With OSPF Demand Circuit, the initial sync of the link state db and
>subsequent changes to link state db triggers call.
>With interesting traffic defined, the interesting traffic triggers call.
>
>As far as I know, it seems that with the exception of Backup Interface,
>these triggering methods aren't mutually exclusive, so it's possible, for
>example, to have both OSPF Demand Circuit and Interesting traffic both in
>effect and both trigger calls. In other words, when both features are in
>effect, either OSPF Demand Circuit or Interesting traffic can trigger a
>call.
>
>The 2nd issue - what traffic transits an isdn link when it's up - is
>independent of what triggers the call. The way I understand it, once the
>link is up any traffic that should transit the link will transit the link.
>So, if you don't want CDP traffic to cross the link when it's UP, disable
>CDP on that interface, regardless of what caused the link to come up in the
>first place.
>
>Another issue to keep in mind, is what causes the isdn link to go down and
>when should the link come down. "Normally", the absense of interesting
>traffic for the dialer idle-timeout period. But, I believe there are other
>factors that may have a role in how this issue is handled.
>
>HTH, dt
>
>
>
>----- Original Message -----
>From: "Jonathan V Hays" <jhays@jtan.com>
>To: "'Nawaz, Ajaz'" <Ajaz.Nawaz@bskyb.com>; "'Donny MATEO'"
><donny.mateo@sg.ca-indosuez.com>; "'Peng Zheng'" <zpnist@yahoo.com>
>Cc: <ccielab@groupstudy.com>; <nobody@groupstudy.com>
>Sent: Thursday, September 25, 2003 9:31 AM
>Subject: RE: Should I disable cdp on ISDN
>
>
> > Now you've got my curiosity up. Exactly how does CDP interact with an
> > OSPF demand circuit?
> >
> > I'm not trying to criticize or flame here - I am ignorant and would like
> > to know. A preliminary search of the Doc CD does not have any
> > information tying CDP to OSPF.
> >
> > Please help,
> >
> > Jonathan
> >
> >
> > -----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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