How do I config a router with LLC link to use a ISDN line as backup?

[dm318]

Hi all, I am kinda lost and not sure what to config. I am using a Cisco 2611 that is connected to a WAN link via the serial port. I also need to set up an ISDN BRI link for backup. How do I config this backup or failover portion? Really appreciate it if any one of you can help. BIG BIG thank you in advance!!!

 

[gconnect]

the bulk of the backup configuration will go on the serial interface

serial 0/1
ip address X.X.X.X 255.255.255.0
backup interface bri0
backup delay 5 30
encap ppp
bandwidth 1544



'backup delay 5 30' basically says, "use the backup interface, bri0 if ser0 goes down for 5 seconds, but after the primary interface s0 comes back up for 30 seconds, take bri0 down and start using s0 again"

or you can use 'backup delay 0 30' and start using bri0 immediatedly after the s0 goes down


Get Connected - I.T.

 

[gconnect]

oh yeah, you can also use the 'backup load' option

serial 0/1
ip address X.X.X.X 255.255.255.0
backup interface bri0
backup load 75 20
encap ppp
bandwidth 1544

'backup load 75 50' says, "bring up bri0 to help out if the load on ser0/1 link becomes 75% loaded, and bring it down only when the load on s0 is 20% or lower

http://www.cisco.com/en/US/products...figuration_guide_chapter09186a0080087225.html

Get Connected - I.T.

 

[dm318]

Thank you gconnect! I'll try it and hope it works!

 

[dm318]

One other question gconnect, what about the ip route statement? As both my serial and BRI link are using static IPs on both ends, does that mean I need to assign two default routes on the router like this? Thanks folks for the help!

!
interface Serial0/0
backup delay 30 60
backup interface BRI0/0
ip address 2xx.xxx.xxx.254 255.255.255.252
no ip redirects
no ip unreachables
no fair-queue
no cdp enable
!
interface BRI0/0
bandwidth 128
ip address 2xx.xxx.xxx.250 255.255.255.252
encapsulation ppp
dialer map ip 2xx.xxx.xxx.249 name xxxxxxxx broadcast xxxxxxx
dialer load-threshold 64 either
dialer-group 1
isdn switch-type basic-net3
no cdp enable
ppp authentication chap
ppp multilink
!
ip classless
ip route 0.0.0.0 0.0.0.0 2xx.xxx.xxx.249
ip route 0.0.0.0 0.0.0.0 2xx.xxx.xxx.253
![/quote]

 

[rburke]

For you backup link you could probably assign a "floating" static route. Since the backup link will only be active when the primary link is down then for your routing statments I would add this:


ip route 0.0.0.0 0.0.0.0 2xx.xxx.xxx.253
ip route 0.0.0.0 0.0.0.0 2xx.xxx.xxx.249 200

The "200" at the end of the routing statement for your backup line means that it's administrative distance is MUCH higher so if your primary link is good, then the primary link will always be used. But if that link goes down then the router will fall back to this backup link default route and will use it instead.

Let me know if this helps.

Burke