Problem with SLAs and WAN load sharing

[Emmanouil Patiniotakis]

Hello,

i am trying to achieve a load sharing with cisco 837. The topology is the one showed below:

I want to track each connection so that if for example there is not connectivity through modem/router, this route get deleted from the routing table. So i have created the ip slas:

ip sla monitor 1

type echo protocol ipIcmpEcho 4.2.2.2 source-interface Dialer0

timeout 500

frequency 5

ip sla monitor schedule 1 life forever start-time now

ip sla monitor 2

type echo protocol ipIcmpEcho 4.2.2.2 source-interface Ethernet2

timeout 500

frequency 5

ip sla monitor schedule 2 life forever start-time now




track 1 rtr 1 reachability

!

track 2 rtr 2 reachability

The first sla is for checking that there is connectivity via ADSL and the second that there is connectivity through the other modem/router (because eth 2 could be up but modem/router has lost internet connectivity)

and then i added two default routes that use the track objects:

ip route 0.0.0.0 0.0.0.0 Dialer0 track 1

ip route 0.0.0.0 0.0.0.0 192.168.1.254 track 2

The result is that the track objects are always down because (???) there is no route for the packets and the debug ip packet commend shows:

s=192.168.1.253 (local), d=4.2.2.2, len 64, unroutable

even though the modem/router is reachable and has a valid connection to the Internet. Does anyone have any idea how i can override this problem?

[cisco_community_user1 · Accepted solution]

Dear,

Can you please verify if the dialer interface is up or not, if its up it must have installed a default route towards dialer interface.

Modify the configs as followed

Modify 4.2.2.2 in IP slap 1 and change it to 4.2.2.1 and leave ipsla2 as it is

Put 2 static routes I.e

IP route 4.2.2.1 255.255.255.255 dialer1

IP route 4.2.22 255.255.255.255 Ethernet 0 or far0/1 or whatever it is

Let me know the outcome.

Thanks

M

Sent from Cisco Technical Support Android App

[Emmanouil Patiniotakis]

Without applying the modification you suggested, even though Dialer interface is up no default route is installed because of track 1 failure. Is this reasonable?

I will make the modification you said and i will cone back...

Thanks for your help.

[fb_webuser]

Well not a big problem..once SLAs are up default route will take over..please proceed with the suggested modifications

Musab

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Posted by WebUser Musab Kiani from Cisco Support Community App

[Emmanouil Patiniotakis]

Thanks my friend...Your solution seems to work great. If you have not problem i would like to mane another question. I have read that load balancing may cause some problems with https site (e.g. e-banking). Is there any way to force the specific traffic to follow a specific road (when this "road" ia active) but auto failover to the other exit when the first is down?

[Emmanouil Patiniotakis]

And something else, does anyone knows why cisco 837 do not support event manager?

[fb_webuser]

Welcome,

You don't need to worry about that, just make sure the load sharing over both links is per-destination which is default behavior of cef.

Just make sure CEF is enabled. If you don't want to use both links as active active, put AD in the end of the default route you want to use as just fail-over.

You can do

sh ip cef 0.0.0.0/0

detail and verify if the load-sharing is per-destination based or not.

Regards

Musab

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Posted by WebUser Musab Kiani from Cisco Support Community App