ISDN - DDR Problem.

vijayakumar.v · ‎02-23-2005

Hi All,

I'm facing a peculiar problem with ISDN on few of my 1700 series routers, I'm using ISDN with DDR as backup for the primary link.

The problem is, ISDN doesn't trigger a call even when there is interesting traffic available. However when I debug dialer packets I can see match for interesting packets, but still ISDN doesn't initiate a call. But when I try to trigger a call manually (using ISDN test call command) its working fine, so it does means that the ISDN line is perfectly ok.

I have attached the ISDN related config Im using, can somebody give your inputs on this..

*******************************************

interface BRI1/0

no ip address

encapsulation ppp

dialer pool-member 1 max-link 1

isdn switch-type basic-net3

interface Dialer1

ip address 10.66.254.8 255.255.255.0

encapsulation ppp

dialer pool 1

dialer string 951123746292

dialer-group 1

ppp authentication chap

dialer-list 1 protocol ip permit

*********************************************

My router model is 1760 and the IOS version is 12.3.1a

Regards

Vijay.

Kevin Dorrell · ‎02-23-2005

Since tghe ISDN test call is working, I presume it is a problem with the ppp or with the backup mechanism itself. You say it does not initiate the call, but are you sure of this? If you do show isdn history or a debug dialer event, do you not see any calls being attempted?

I presume you are using a floating static to trigger the ISDN call? Perhaps there is some problem with the floating static. Could you post the rest of the configuration, especially the mechanism that is supposed to provoke the call?

Kevin Dorrell

Luxembourg

vijayakumar.v · ‎02-23-2005

Hi Kevin,

The show isdn history or debug dialer event doesn't given any output....meaning it not showing that any calls are being attempted.

And you are right we are using floating static to trigger the ISDN call, but that is when the primary link is down. No cosider this case..when my primary link is up and I want to trigger the ISDN call..

And I have permitted any traffic as interesting ( if you refer my dialer-list command you can see that), so any traffic.. say routing protocol traffic would also be an interesting traffic for the ISDN to trigger a call. But thats not happening...even in the debug dialer packets it shows the match of interesting packets...its not triggering a call.

The output of debug dialer packets are like this...

Feb 23 15:43:05.546: Di1 DDR: ip (s=10.66.254.8, d=224.0.0.5), 76 bytes, outgoin

g interesting (ip PERMIT)

so here in the above you can see "224.0.0.5" ospf packet getting mactched for the interesting packet, but still call is not getting triggered.

Also find the whole config in the router. (I have marked xxxx and nnn some places, because I won't able to provide those informations as per the clients security policy)

version 12.3

service tcp-keepalives-in

service timestamps debug datetime msec

service timestamps log datetime msec

service password-encryption

!

logging buffered 32768 debugging

no logging console

enable secret xxxxx

!

username xxxxxx password xxx

ip subnet-zero

no ip source-route

!

no ip domain lookup

!

ip audit notify log

ip audit po max-events 100

no ftp-server write-enable

isdn switch-type basic-net3

!

policy-map voice

class voice_stream

priority 16

compress header ip rtp

class voice_signaling

bandwidth 8

class class-default

fair-queue

!

interface Loopback0

ip address 10.127.2.166 255.255.255.255

!

interface Multilink1

bandwidth 64

ip address 10.126.13.26 255.255.255.252

service-policy output voice

ppp multilink

ppp multilink fragment delay 10

ppp multilink interleave

ppp multilink group 1

!

interface FastEthernet0/0

ip address 10.67.38.1 255.255.255.0

no ip route-cache

speed 10

half-duplex

!

interface Serial0/0

bandwidth 64

no ip address

encapsulation ppp

no fair-queue

ppp multilink

ppp multilink group 1

!

interface BRI1/0

no ip address

encapsulation ppp

dialer pool-member 1 max-link 1

isdn switch-type basic-net3

!

interface Dialer1

ip address 10.66.254.8 255.255.255.0

encapsulation ppp

dialer pool 1

dialer string 951123746292

dialer-group 1

no cdp enable

ppp authentication chap

!

router ospf 20

log-adjacency-changes

area 27 stub

network 0.0.0.0 255.255.255.255 area 27

!

ip classless

ip route 0.0.0.0 0.0.0.0 10.66.254.1 250

no ip http server

no ip http secure-server

!

dialer-list 1 protocol ip permit

!

line con 0

password xxxx

login authentication NO_AUTH

line aux 0

line vty 0 4

password 7 xxxx

!

end

Regards

Vijay.

Kevin Dorrell · ‎02-23-2005

Normally I do not think an OSPF multicast will trigger an ISDN dialer, but I'm still a bit hazy about the status of OSPF and demand-circuits. I think that normally you would configure ip ospf demand-circuit on the dialup, but I'm not sure what the repercussion are if you do not. For that I would have to hand over to someone who already knows how OSPF behaves in such an environment. Here is a document for us both to read, anyway.

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094a8f.shtml

Getting back to the ISDN, if you show ip route, do you see a route to 10.66.254.0/24 as directly connected ion Dialer1? What happens if you ping 10.66.254.1, does it open a call? Try setting ip route 10.66.254.1 255.255.255.255 Dialer1.

Let us know how you get in with this.

Here is another document I have not read yet, but looks as if it might contain some relevant information.

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094052.shtml

Kevin Dorrell

Luxembourg

mahesh_illuri · ‎02-23-2005

Hi vijay,

configure acceslist in the router which defines your interesting traffic.

regards

mahesh illuri

Richard Burts · ‎02-23-2005

Vijay

Thanks for providing the config information. I am not seeing an obvoius problem in the config. Can you post the output of show isdn status.

Also can you provide some more information about what happens when you attempt to dial. Perhaps the output of debug isdn q931 would be helpful to show what is happening with ISDN. Also the output of deb ppp authentication and deb ppp negotiation.

HTH

Rick

HTH

Rick

Kevin Dorrell · ‎02-23-2005

Rick,

With this configuration, in the absence of ip ospf demand-circuit, would you normally expect the OSPF Hello to open the call? I realise the command normally suppresses the hellos and flags a no-update, but what is the behaviour if you leave out the command and treat it as a normal (point-to-point, NBMA, or point-to-multipoint?) interface?

Kevin Dorrell

Luxembourg

Richard Burts · ‎02-23-2005

Kevin

Yes with ip ospf demand-circuit you do need to define OSPF hellos as interesting traffic and an OSPF hello would bring the circuit up. And hello does bring the circuit up at the beginning. It stays up long enough to establish the neighbor relationship and to syncronize the OSPF data base. After that OSPF does not send hello on the demand circuit to maintain the neighbor relationship as it would do on normal connections. So hello will not continually bring up the connection.

Your question was about configurations that do not use demand-circuit. If the configuration does not use demand-circuit and if OSPF hello is interesting traffic, then I would expect that the connection would come up and stay up permanently. (Do this only if you are lucky enough to have flat rate ISDN.)

I have seen people configure routers without demand-circuit in which they define OSPF hello as non-interesting traffic and with something else that will bring up the connection. When the connection is up OSPF hellos are sent (non-interesting traffic is transmitted when the circuit is up but will not bring it up or keep it up) and neighbor relationships are formed. But when the interresting traffic stops the circuit comes down and the neighbor relationship is lost.

HTH

Rick

HTH

Rick

riz_432 · ‎04-30-2005

try pinging 10.66.254.1 this should get the call established and when ur primary link is up the router will always pass the interresting traffc as according to ur configuration through the primary link and hence call isdn call wont get established. while ur primary link is up the call will get established only when u try to ping the 10.66.254.0 subnet. And if the Primary link goes down the back up link takes the place in the routing table and isdn will get fired.

mahesh_illuri · ‎02-23-2005

I don't think you'll get a satisfactory answer to this question, without some more information.

What is your interesting traffic?

How did you define interesting traffic ?

regards

Mahesh Illuri

Kevin Dorrell · ‎02-23-2005

Mahesh,

I think he answered that in his original posting: dialer-list 1 protocol ip permit .

Kevin Dorrell

Luxembourg