ISDN Backup on a 1600

[mbrookes]

Hello,

I have a 1601 with ISDN backup on a 256k Leased Line with HDLC encapsulation.

If the line goes down the ISDN backup doesn't kick in after what should be 3 failed keepalives on the serial interface. The only way of bringing up the ISDN backup is to pull the X21 cable out of the router, forcing the ISDN to dial.

This causes issue with, when the line comes up it doesn’t automatically go back to the LL, and if there is no one technically competent (or confident) enough to remove the X21 when the line goes down, there will be no connectivity due to the ISDN not coming up.

Can anyone shed any light, or any possible solution??

 

[pmesjar]

How is your backup configuration created? Are you using backup interfaces? Maybe it would be easier to look at your problem if you post the config...

Peter Mesjar
CCNP, A+ certified
pmesjar@centrum.sk

"The only true wisdom is in knowing you know nothing.

 

[mbrookes]

Yeah, sorry about that:

Yeah, sorry about that:

version 12.0
no service pad
no service udp-small-servers
no service tcp-small-servers
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname router
!
aaa new-model
aaa authentication login default tacacs+ enable
aaa authentication enable default tacacs+ enable
aaa accounting exec start-stop tacacs+
aaa accounting commands 15 start-stop tacacs+
aaa accounting system start-stop tacacs+
!
enable password <removed>
!
username <removed> password <removed>
ip subnet-zero
no ip source-route
no ip finger
ip domain-lookup
ip name-server <removed>
ip name-server <removed>
isdn switch-type basic-net3
isdn tei-negotiation first-call
!
interface Ethernet0
description Local Ethernet Interface
ip address <removed>
no ip directed-broadcast
no shutdown
!
interface Serial0
description Leased Line Connection
backup delay 5 5
backup interface BRI0
ip unnumbered Ethernet0
no fair-queue
no shutdown
!
interface BRI0
description ISDN Backup to Leased Line
ip unnumbered Ethernet0
encapsulation ppp
dialer idle-timeout 2147482
dialer wait-for-carrier-time 10
dialer map ip <removed>
dialer map ip <removed>
dialer load-threshold 255 either
dialer-group 1
ppp authentication chap callin
no shutdown
!
ip classless
ip route 0.0.0.0 0.0.0.0 Serial0
ip route 0.0.0.0 0.0.0.0 <removed> 200
ip route <removed> 255.255.255.255 BRI0 200
access-list 102 permit ip any any
snmp-server trap-authentication
snmp-server enable traps config
snmp-server enable traps frame-relay
snmp-server enable traps isdn call-information
snmp-server host <removed> wildduck
dialer-list 1 protocol ip list 102
dialer-list 1 protocol ipx list 901
tacacs-server host <removed>
tacacs-server host <removed>
tacacs-server key <removed>
banner motd c
Star Internet Ltd
Authorised Use Only
c ^C
!
line con 0
line vty 0 4
password <removed>
login
!
end

 

[Jsteve]

I believe I see to problems that may account for some of your problems

1. your "dialer idle-timeout 2147482" command is set way too high. this is why the line goes down and the ISDN backup doesn't kick in right away. It should be set for 20-30sec (tweekable)

2.your "dialer load-threshold 255 either" is set to kick in when your bandwitrh has reached 100% capacity. Try lowering this to "dialer load-threshold 10 either" to see if the back up kicks in when the link goes down.

My two cents

 

[mbrookes]

Jsteve, thanks for the help, but although the dialer timeout does seem high, this is so that the line does not constantly redial, causing excessive costs. If the serial line went down and ISDN came up properly then with activation of the serial line, this would take over from the ISDN.

With the threshhold, this again is only ISDN specific and will surely not affect the problem, as it is only to do with the loading of the ISDN line.

And would make the line come up. HDLC will drop the IPs from the routes after 3 missed keep alives as I understand it, then the ISDN backup will kick in.

This is the issue, despite their being connection on the serial interface, somehow the router thinks that the route is present and does not fail-over.

 

[Jsteve]

I see.

could your problem be because your using ip unnumbered on your serial interface and E0 need to go down before the ISDN kicks in?

 

[Jsteve]

although the dialer timeout does seem high, this is so that the line does not constantly redial, causing excessive costs. If the serial line went down and ISDN came up properly then with activation of the serial line, this would take over from the ISDN.[/i}

As for this situation, I think it depends on the type of traffic and the longest quiet duration during an establish connection. you should researh this and adjust your dialer timeout accordingly, otherwise you will always have to manually disconnect the call when the serial line comes back up or wait the dialer timeout whaich you have set for 24days.

 

[gconnect]

the 'dialer load-threshold' tells you when the second B channel should come up. I personally, usually set that to 1 so that i can use the most bandwidth out of the situation. the 'dialer idle-timeout' is the setting for when to take the link down if no interesting traffic runs across the link. having it set high like that is also fine, although you also have it set for 'backup delay 5 5' which means that the line will come up after 5 seconds of being down and go down 5 seconds after the mainline comes back up.


NOW you need to post the 'dialer-map' and username/passwd (modified with fake name/numbers) stuff because if the Phone Number is not bound correctly then the link will never come up. I think your problem may lie here.....


what does your 'show isdn status' command show you? does it say MULTIPLE_FRAME_ESTABLISHED? if not than the problem is in between your device and the telco switch and should be fixable by looking at the 'debug dialer' and 'debug isdn XXXX' commands.

p.s. Is that the correct switch-type. I usually bump into basic-5ess switch types




-gC-

 

[gconnect]

and oh yeah, if you shut the primary interface down using the 'shutdown' command, the secondary will not dial. the only way for it to dial is if the interface is actually down..

-gC-

 

[Jsteve]

Any results to report??