IP SLA usage

Posted on 2008-10-04
Last Modified: 2012-06-21
Hi all

I am trying to setup a 3G card in a router to automatically connect to our MPLS network if the serial interface dies.  The cellular interface is setup as backup to the serial interface.  To transfer proper EIGRP routes, I have to setup an MGRE tunnel, which I have.  Sprint service drops all cellular connections when unknown traffic flows over the wireless connection, but I have to generate traffic to establish the cellular connection (So I cannot run a continous ping from an inside source without the MGRE tunnel established).  When the serial interface goes down, the router loses all routes, therefore no traffic is attempted.  In order to dial the cellular interface and then the MGRE tunnel to transfer EIGRP, I have to generate traffic by manually pinging the MGRE destination.  I have a static host route as needed to this destination through the cellular interface.

So that long explanation is to show why I am asking this question..  I want an IP SLA process to "attempt" a constant ping to an address, sourced from the cellular interface, that then only works when the serial interface is down.

Here is my relavant config.  I still have to manually ping to establish the MGRE tunnel and relevant connection, but once that occurs, everything works well and EIGRP allows all network connectivity.  What am I missing to get the router to automatically ping the addresses when the cellular interface does come up?

router#sho run
Building configuration...

Current configuration : 2288 bytes
version 12.4

interface Tunnel0
 bandwidth 10000
 ip address
 ip nhrp authentication MGRE
 ip nhrp map
 ip nhrp map multicast
 ip nhrp network-id 192168250
 ip nhrp holdtime 300
 ip nhrp nhs
 ip nhrp cache non-authoritative
 tunnel source Cellular0/1/0
 tunnel destination
 tunnel key 100000
interface FastEthernet0/0
 ip address
 duplex auto
 speed auto
interface Serial0/0/0
 backup interface Cellular0/1/0
 ip address
interface Cellular0/1/0
 ip address negotiated
 encapsulation ppp
 dialer in-band
 dialer idle-timeout 3600
 dialer string cdma
 dialer-group 1
 async mode interactive
router eigrp 100
 no auto-summary
ip route Cellular0/1/0
ip sla 1
 icmp-echo source-interface Cellular0/1/0
 frequency 10
ip sla schedule 1 life forever start-time now
access-list 1 permit any
dialer-list 1 protocol ip list 1
line 0/1/0
 exec-timeout 0 0
 script dialer cdma
 modem InOut
 no exec
 transport input all
 rxspeed 3100000
 txspeed 1800000
Question by:vppinc
  • 2
LVL 13

Expert Comment

ID: 22654561
Had a brief look at it, and noticed a couple things:

- You're not tracking a route for SLA. Add an initial default route to your serial link that is tracked, then another to the cellular connection.
- Set the idle-timeout to 0

Author Comment

ID: 22868704
I contacted Cisco about this and they suggested the following configuration.

track 151 rtr 151 reachability
 delay down 10 up 60
ip sla 151
 icmp-echo source-interface serial0/0/0
 frequency 10
ip sla schedule 151 life forever start-time now
event manager applet bring-up-celluar
 event track 151 state down
 action 1 cli command "conf t"
 action 2 cli command "ping"
 action 3 cli command "end"

However, the track 151 rtr command fails at "rtr", and the event Manager command is not available.  Any further assistance would be helpful.

Accepted Solution

vppinc earned 0 total points
ID: 22976213
Gotta have the Advanced IP services to perform the steps needed.  

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