09-24-2005 06:58 AM - edited 03-03-2019 10:34 AM
We are in the process of setting up a remote site. We are using BT to provide a point to point leased line and an ISDN30 PRI at both sites. Only 15 of the E1 channels will be enabled. We are using cisco 2800 routers with a single port serial wic card and a single port ISDN PRI network module in each. The PRI link is to be used as a backup in case of serial link failure I would appreciate detailed advice and guidance on the following:-
1) how to configure /enable the E1 controller (given that it is provided by BT and we are only using ½ of the channels)
2) How to set up the interfaces so that the router will automatically fail over to the PRI link
Thanks
09-24-2005 07:26 AM
Hi Reeces,
You can use backup interface
This link will guide you with the config for backup links
http://www.networkingunlimited.com/white004.html
HTH
Ankur
09-24-2005 07:42 AM
Hello,
first of all, the configuration of your E1 controller would look like this:
controller E1 1
framing crc4
linecode hdb3
clock source line secondary
pri-group timeslots 1-15
The parameters might be slightly different than the ones used here, depending on your provider.
Next, the D-channel interface configuration would look like this:
interface Serial1:0:15
no ip address
encapsulation ppp
dialer pool-member 1
dialer pool-member 1 min-link 14
isdn switch-type primary-net5
no cdp enable
ppp authentication chap
ppp multilink
Then, you would create a dialer interface for the connection to the other side:
interface Dialer1
ip address 192.168.1.1 255.255.255.252
encapsulation ppp
dialer pool 1
dialer remote-name Remote1
dialer string 123456
dialer-group 1
ppp authentication chap
ppp multilink
Regarding the backup method, it depends on if and what routing protocols you are using. The easiest way to configure the backup would be to include the statement 'backup interface dialer 1' on your main serial interface, that is, the serial interface of the leased line. Other options, such as dialer watch, or snapshot routing, are available as well, depending on, as said before, the routing protocols you are using.
Hope I did not forget anything. Of course, make sure you are either using local username and password for the CHAP (if you use CHAP) or have that configured in e.g. an ACS.
Let me know if you run into trouble...
Regards,
GP
09-25-2005 02:44 AM
Hi, Many thanks for the information - most helpful. A couple of questions though -
1) I presume I need to set up an access list for the dialer1 interface to define 'interesting' traffic for it to actually be brought up as a backup
2) I will be using static routes rather than any routing protocol - My serial link and Dialer will be on seperate networks so I guess I need to set two static routes for every destination - one for the serial link and one for the Dialer?
3) Any special config required for this or is it simply a matter of setting two static routes up?
09-25-2005 06:46 AM
Hi Reces,
Yes you have to configure access list and call that access list in dialer list to define your interesting traffic.
It will be something liek this
interface dialer 1
dialer-group 1
!
dialer list 1 protocol permit ip 101
!
access-list 101 deny x.x.x.x
access-list 101 permit ip any any
This way you can configure your interesting traffic and can configure your access list as per your wish and requirement.
HTH
Ankur
09-25-2005 08:04 AM
Hello,
when you use the ´backup interface dialer 1´ command under your serial interface, you do not need to specify an access list for your interesting traffic, the dialer interface will be up/up (spoofing), which means it will not route any traffic unless the main interface goes down. So the statement ´dialer-list 1 protocol ip permit´ would be sufficient.
As for the static routes, yes, just configure two default routes with different administrative distances:
ip route 0.0.0.0 0.0.0.0 Serial0
ip route 0.0.0.0 0.0.0.0 Dialer1 200
HTH,
GP
09-26-2005 04:05 AM
and I presume that a dialer string needs only to be specified on one side of this simple point-to-point example as you wouldn`t want both routers to try and dial each other if there is a failure?
09-26-2005 08:45 AM
And finally,
Things are almost working but when failing over to the ISDN E1, only one channel is brought up. I enclose what I believe to be the appropriate bits of config as I think it is likely a config error as I want to bring all available chnnels up.
controller E1 1/0
pri-group timeslots 1-16
interface Serial1/0:15
no ip address
encapsulation ppp
dialer pool-member 1 min-link 14
isdn switch-type primary-net5
no cdp enable
ppp authentication chap
ppp multilink
!
interface Dialer1
ip address 10.20.0.2 255.255.255.0
encapsulation ppp
dialer pool 1
dialer remote-name XXXXXXXX
dialer string XXXXXXXXXXX
dialer-group 1
no cdp enable
ppp authentication chap
ppp multilink
access-list 101 remark Intersting Traffic Definition for Backup Link
access-list 101 permit ip any any
dialer-list 1 protocol ip list 101
09-26-2005 09:46 AM
Hello,
try and add ´ppp multilink links minimum 14´ to your dialer 1 interface configuration.
Regards,
GP
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