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I'm trying to configure a couple of Cisco 1941 routes. The are both identical routers. Each as a HWIC-1T (Smart Serial interface) and a HWIC-3G-HSPA 3G interface. These routers are to be sent to remote sites. We have connectivity to one of the sites but if remote site A gors down we lose connectivity to remote site B.

The HWIC-1T is the primary WAN interface using frame relay joining the two remote sites

We want the HWIC-3G-HSPA to be usable for direct connectivity from head office to remote site B, and also the HWIC-3G-HSPA is do be used for comms between the remote sites when the frame relay is down (happens quite a bit).

I initialy tried to do dynamic routing using EIGRP however in my lab setup of laptop - 1941 - 1941 - laptop, I was unable to get end to end connectivity. I later settled on static routing and have got end to end connectivity but only over frame relay, not the HWIC-3G-HSPA.

The sanitized running config for remote site A:

version 15.1
service tcp-keepalives-in
service tcp-keepalives-out
service timestamps debug datetime msec
service timestamps log datetime msec
service password-encryption
service udp-small-servers
service tcp-small-servers
!
hostname remoteA
!
boot-start-marker
boot-end-marker
!
!
logging buffered 51200 warnings
enable secret 5 censored
!
no aaa new-model
clock timezone wst 8 0
!
no ipv6 cef
ip source-route
ip cef
!
ip domain name yourdomain.com
multilink bundle-name authenticated
!
chat-script gsm "" "ATDT*98*1#" TIMEOUT 30 "CONNECT"
!
username admin privilege 15 secret 5 censored
!
controller Cellular 0/1
!
interface Embedded-Service-Engine0/0
 no ip address
 shutdown
!
interface GigabitEthernet0/0
 ip address 192.168.2.5 255.255.255.0
 duplex auto
 speed auto
!
interface GigabitEthernet0/1
 no ip address
 shutdown
 duplex auto
 speed auto
!
interface Serial0/0/0
 ip address 10.1.1.2 255.255.255.252
 encapsulation frame-relay
 cdp enable
 frame-relay interface-dlci 16
 frame-relay lmi-type ansi
!
interface Cellular0/1/0
 ip address negotiated
 encapsulation ppp
 dialer in-band
 dialer idle-timeout 2147483
 dialer string gsm
 dialer-group 1
 async mode interactive
 ppp chap hostname censored
 ppp chap password 7 censored
 cdp enable
!
interface Cellular0/1/1
 no ip address
 encapsulation ppp
!
interface Dialer0
 no ip address
!
ip forward-protocol nd
!
no ip http server
no ip http secure-server
!
ip route 0.0.0.0 0.0.0.0 Serial0/0/0 210 permanent
ip route 0.0.0.0 0.0.0.0 Cellular0/1/0 220 permanent
ip route 172.31.2.0 255.255.255.0 Cellular0/1/0 permanent
ip route 192.168.3.0 255.255.255.0 10.1.1.1 permanent
ip route 192.168.3.0 255.255.255.0 Cellular0/1/0 210 permanent
!
access-list 1 permit any
dialer-list 1 protocol ip list 1
!
control-plane
!
line con 0
 logging synchronous
 login local
line aux 0
line 2
 no activation-character
 no exec
 transport preferred none
 transport input all
 transport output pad telnet rlogin lapb-ta mop udptn v120 ssh
 stopbits 1
line 0/1/0
 exec-timeout 0 0
 script dialer gsm
 login
 modem InOut
 no exec
 transport input all
 rxspeed 7200000
 txspeed 5760000
line 0/1/1
 no exec
 rxspeed 7200000
 txspeed 5760000
line vty 0 4
 access-class 23 in
 privilege level 15
 password 7 censored
 login local
 transport input all
line vty 5 15
 access-class 23 in
 privilege level 15
 password 7 censored
 login local
 transport input all
line vty 16 1370
 password 7 censored
 login
 transport input all
!
scheduler allocate 20000 1000
end

The sanitized running config for remote site B:

version 15.1
service tcp-keepalives-in
service tcp-keepalives-out
service timestamps debug datetime msec
service timestamps log datetime msec
service password-encryption
service udp-small-servers
service tcp-small-servers
!
hostname remoteB
!
boot-start-marker
boot-end-marker
!
logging buffered 51200 warnings
enable secret 5 censored
!
no aaa new-model
clock timezone wst 8 0
!
no ipv6 cef
ip source-route
ip cef
!
no ip domain lookup
ip domain name yourdomain.com
multilink bundle-name authenticated
!
chat-script gsm "" "ATDT*98*1#" TIMEOUT 30 "CONNECT"
username admin privilege 15 secret 5 censored
!
controller Cellular 0/1
!
interface Embedded-Service-Engine0/0
 no ip address
 shutdown
!
interface GigabitEthernet0/0
 ip address 192.168.3.1 255.255.255.0
 duplex auto
 speed auto
!
interface GigabitEthernet0/1
 no ip address
 shutdown
 duplex auto
 speed auto
!
interface Serial0/0/0
 ip address 10.1.1.1 255.255.255.252
 encapsulation frame-relay
 clock rate 2000000
 cdp enable
 frame-relay interface-dlci 16
 frame-relay lmi-type ansi
 frame-relay intf-type dce
!
interface Cellular0/1/0
 ip address negotiated
 encapsulation ppp
 dialer in-band
 dialer idle-timeout 2147483
 dialer string gsm
 dialer-group 1
 async mode interactive
 ppp chap hostname censored
 ppp chap password 7 censored
 ppp ipcp dns request
 cdp enable
!
interface Cellular0/1/1
 no ip address
 encapsulation ppp
!
interface Dialer0
 no ip address
!
ip forward-protocol nd
!
no ip http server
no ip http secure-server
!
ip route 0.0.0.0 0.0.0.0 Serial0/0/0 210 permanent
ip route 0.0.0.0 0.0.0.0 Cellular0/1/0 220 permanent
ip route 172.31.2.0 255.255.255.0 Cellular0/1/0 permanent
ip route 192.168.2.0 255.255.255.0 10.1.1.2 permanent
ip route 192.168.2.0 255.255.255.0 Cellular0/1/0 210 permanent
!
kron occurrence PING in 1 recurring
 policy-list ICMP
!
access-list 1 permit any
dialer-list 1 protocol ip list 1
!
control-plane
!
line con 0
 logging synchronous
 login local
line aux 0
line 2
 no activation-character
 no exec
 transport preferred none
 transport input all
 transport output pad telnet rlogin lapb-ta mop udptn v120 ssh
 stopbits 1
line 0/1/0
 exec-timeout 0 0
 script dialer gsm
 login
 modem InOut
 no exec
 transport input all
 rxspeed 7200000
 txspeed 5760000
line 0/1/1
 no exec
 rxspeed 7200000
 txspeed 5760000
line vty 0 4
 access-class 23 in
 privilege level 15
 password 7 censored
 login
 transport input all
line vty 5 15
 access-class 23 in
 privilege level 15
 password 7 censored
 login
 transport input all
line vty 16 1370
 password 7 censored
 login
 transport input all
!
scheduler allocate 20000 1000
end

The last problem I'm having is the 3G interfaces go down after only a few minutes of inactivity. I've tried using kron to ping the local HWIC-3G-HSPA interface (cellular 0/1/0) every minute but that hasn't been successful. Manually pinging the IP assigned (by the telco) to ce0/1/0 does bring the interface up.

Any ideas?

Thanks

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1 Answer

You could set up a fake GRE tunnel in order to send packets to maintain the interface up.

router(config)# int tun0
router(config-if)# ip unnunbered <lan interface>
router(config-if)# tunnel mode gre
router(config-if)# tunnel source <lan interface>
router(config-if)# tunnel dest <default 3G gateway>

The tunnel dest can also be any IP for wich you have a route via 3G. The tunnel will stay down (as the keepalive messages won't be answered) but the keepalives sent will force the 3G interface to stay up.

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