Chris,
What are the specific problems you are seeing the T1 comes back up? The only
routing issues I would look for would be to make sure you have recursive
routing configured wherever you have IP unnumbered configured. Either that,
or I would get rid of ip unnumbered alltogether since this is a private
network, and there is no risk of running out of IP address space.
Does the ISDN router have a recursive host route to the 2.1 address which
says it is reachable through the BRI/dialer?
I think the easiest/cleanest way to do his would be to run the routing
protocol, and have the Remote ISDN router do the dialing when needed. Have
the Central router advertise a default route to the Remote T1 router, which
would also have the floating default route pointing to the ISDN Router. When
the T1 connection is lost, the floating static route is installed, and
traffic is directed to the ISDN router which only needs a static default
route going out its BRI.
Since the remote routers share a LAN segment, you could also look into
implementing HSRP where the Remote T1 router is confiured as the active
router, and therefore receives all traffic from the LAN users who need to
get to the Central site. If that router fails, or if the T1 interface goes
down, the ISDN router now becomes the active router and receives the traffic
from the LAN users and sends it out the ISDN interface.
A combination of floating static routes with a dynamic rouing protocol and
HSRP is a good design to go with, since you achive redundancy on layer 1, 2
and 3. Floating statics with a routing protocol ensure the Remote T1 router
is notified when, for example, the T1 interface on the central site goes
down. In such a case, the T1 interface on the Remote could stay up and
floating statics alone would not notify the Remote T1 router of the loss of
connection. The dynamic routing protocol will. HSRP allows the ISDN router
to be notified when the T1 interface or the ethernet interface on the Remote
T1 router goes down, or when the entire router fails.
michael a.o
>From: "Chris Sees" <[EMAIL PROTECTED]>
>Reply-To: "Chris Sees" <[EMAIL PROTECTED]>
>To: <[EMAIL PROTECTED]>
>Subject: ISDN Backup
>Date: Thu, 9 Nov 2000 14:21:21 -0500
>
>Hi,
>I'm having some issues with ISDN backup failover and hopefully someone has
>done this before.
>
>-Central site with a dedicated T1 through serial int. to Remote site router
>-Central site also has a ISDN to Remote site to a second router
>The Central serial has the BRI as a backup. Also, we are NOT using RIP
>(although this is not out of the question) When we pull the T1 the ISDN
>comes up and everything seems fine. But when the T1 is put back, there are
>very weird things happening. I'm pretty sure its routing, so I've include
>the route commands of each router. Any thoughts, ideas, suggestions would
>be
>greatly appreciated. Thanks.
>
>Chris
>
>
>Central Router
>0.0.0.0 0.0.0.0 192.168.2.10 ---This route goes to the internet
>ip route 192.168.1.0 255.255.255.0 123.123.123.1 -- This goes to the Remote
>site through the T1
> router
>ip route 192.168.1.0 255.255.255.0 Dialer1 50 -- This goes to Remote site
>through ISDN router
>
>Remote Site T1 Router
>ip route 0.0.0.0 0.0.0.0 123.123.123.2 - Goes to Central T1
>ip route 0.0.0.0 0.0.0.0 192.168.1.2 50 - Goes to Central through Remote
>ISDN
> (192.168.1.2 is LAN side of
>ISDN router)
>
>Remote site ISDN Router
>ip route 0.0.0.0 0.0.0.0 192.168.2.1 - 2.1 is ethernet side of Central
>router (ipunnumbered over
> ISDN)
>
>
>Hope this is clear enough.
>
>
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