Dial Backup from 1750 into a 3640

Hi all....I could really use some help on this one.

I have one remote site using a 1750 cisco router. Our HQ uses a 3640
router with a 24port Mica modem module that allows inbound connections.
I have a 3com external modem attached to the 1750 for dial backup if
the E0 int goes down. When I disconnect the e0, the modem dials out to
our 3640 and connects. At that poing, I can ping the 170.1.1.16
address from my workstation. I can't ping anything on the HQ network
from the router,hub, or client on the 1750 network. I also have the
backup interface command pointing to my Async5.


Here are my configs.

Thanks
1750 config

interface Async5
ip address 170.1.1.16 255.255.255.0
encapsulation ppp
keepalive 10
dialer in-band
dialer idle-timeout 300
dialer string 1800xxxxxxx
dialer-group 1
fair-queue
ppp authentication chap
!
interface Dialer1
no ip address
no cdp enable

ip nat inside source route-map nonat interface Ethernet0 overload
ip kerberos source-interface any
ip classless
no ip forward-protocol udp netbios-ns
no ip forward-protocol udp netbios-dgm
ip forward-protocol udp netbios-ss
ip forward-protocol udp xxxxx
ip route 0.0.0.0 0.0.0.0 gateway of ISP
ip route 0.0.0.0 0.0.0.0 Async5 200
no ip http server

access-list 3 permit any
access-list 110 deny ip 192.168.16.0 0.0.0.255 172.16.0.0 0.0.255.255
access-list 110 deny ip 192.168.16.0 0.0.0.255 172.17.0.0 0.0.255.255
access-list 110 permit ip 192.168.16.0 0.0.0.255 any
access-list 120 permit ip 192.168.16.0 0.0.0.255 172.16.0.0 0.0.255.255
access-list 120 permit ip 192.168.16.0 0.0.0.255 172.17.0.0 0.0.255.255
access-list 121 permit ip 192.168.16.0 0.0.0.255 172.16.0.0 0.0.255.255
access-list 121 permit ip 192.168.16.0 0.0.0.255 172.17.0.0 0.0.255.255
priority-list 1 protocol ip high
dialer-list 1 protocol ip permit
route-map nonat permit 10
match ip address 110
********************************************
3640 config

dialer map ip 170.1.1.16 name test
ip route 170.1.1.16 255.255.255.255 192.168.16.1 200
ip route 192.168.16.0 255.255.255.0 170.1.1.16 200

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

Any help would be greatly appreciated.

 

Which physical interface do you have the modem connected to on the
1750?

 

The AUX port

 

OK good. Try adding 'async default routing' on the Async interface. I
know this is required for a routing protocol to run over the link, not
sure if it also required for routing in general.

 

You may need to add the 'async default routing' command on the
Group-Async interface on the 3640 as well.

 

Frequently, this behavior is due to the called router not detecting the need
to use the dial link to get back to the remote site. You don't show the
primary route interfaces, so there is no way to tell how your dial backup
even is supposed to work.

Hint: for dial backup to work, you need to detect the need to dial (loss of
primary link), have a mechanism to dial based on that failure (dialer watch
based on routing protocol exchanges is usually the preferred solution), and
a mechanism so that all routers involved know to use the new route rather
than the old route. Depending on the approach, you may also need something
extra when to switch back to insure that everything goes back the way it is
supposed to.

Good luck and have fun! A show ip route at each end while on dial backup
will probably point you in the right direction for a fix.

 

My Internal network behind the 3640 is 172.17.0.0 and 172.16.0.0.

If on the 1750, I do an ip route 0.0.0.0 0.0.0.0 async5, won't that
route all interesting traffic over the async5 interface?

 

But what is the route on the 3640 to get back to the 1750? That is where
most static routed dial backup schemes get it wrong. Have you done a "show
ip route" at both routers while on dial backup as I suggested in my
previous response?

Good luck and good hunting!

 

You should be using dynamic routing, EIGRP. I did a 20+ site solution using
these same routers with multiple T1s and ISDN BRI to PRI dialup. Worked
perfect and I haven't had to change it in years. My client never even
noticed when one of the T1s went down and the traffic was rerouted through
another site, thank God I had it configured to notify my syslog or they may
have stayed that way.

I do have a question, are you using VoIP? The 1750 is a VoIP router and I
don't thinks it's going to work very well over a modem connection.


--
RC
rcohen _ "at" _ cominc _ "dot" _ net remove all _ and spaces

The only thing I guaranty about my free advice is that it's mine and it's
free.