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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.

Reply to
computertech33
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Which physical interface do you have the modem connected to on the

1750?
Reply to
Robert B. Phillips, II

The AUX port

Robert B. Phillips, II wrote:

Reply to
computertech33

Reply to
Robert B. Phillips, II

Reply to
Robert B. Phillips, II

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.

Reply to
Vincent C Jones

Reply to
computertech33

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!

Reply to
Vincent C Jones

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.

Reply to
RC

It's just a data connection.

The good news is that I now have the client attached to the 1750 pinging the internet by IP and FQDN...The weird thing is, I can't browse with IE. I can connect the laptop to my internal network and it browses fine, so it is not a client issue or IE issue.

Any help would be greatly appreciated.

test#sh run Building configuration...

Current c> You should be using dynamic routing, EIGRP. I did a 20+ site solution using

Reply to
computertech33

Two monster problems with this config:

1 - about the only time the Async5 interface will be enabled is when the Ethernet is pulled from the socket. Normal communications failures do not cause an Ethernet interface to register as down.

2 - ip nat ...route-map... is only applied to a NAT when the NAT is initially set up. Once a NAT is in the translation table, that NAT will always be used even if the interface changes.

Both of these problems have been discussed to death in this forum (Hansang, are you still there? this belongs in the FAQ). Try searching on "object tracking" (Cisco's name) or "ping based routing" (the common name) for prior discussions on why this approach will not work and ways to get around the problems.

Good luck and have fun!

Reply to
Vincent C Jones

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