ISR1100 Problem with ICMP when sla are enabled

[Sakura]

Hi,

I have a ISR1100 (C1111) with two connections: fiber (GiE0/0/0) and LTE (Cellular0/2/0).

Config excerpt:

ip route 0.0.0.0 0.0.0.0 100.64.107.1 name primary track 1
ip route 0.0.0.0 0.0.0.0 Cellular0/2/0 10 name backup
!
ip sla 1
icmp-echo 8.8.8.8 source-interface GigabitEthernet0/0/0
ip sla schedule 1 life forever start-time now

With this configuration, I cannot do any ping from GiE0/0/0 interface:

router#ping 8.8.8.8 source GigabitEthernet 0/0/0
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 8.8.8.8, timeout is 2 seconds:
Packet sent with a source address of 100.72.88.141
.....
Success rate is 0 percent (0/5)
router#ping 8.8.8.8
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 8.8.8.8, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 48/56/64 ms

If I disable the secondary route (Cellular0/2/0) then the ping works correctly.

router(config)#no ip route 0.0.0.0 0.0.0.0 Cellular0/2/0 10 name backup
router(config)#end
router#ping 8.8.8.8 source GigabitEthernet 0/0/0
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 8.8.8.8, timeout is 2 seconds:
Packet sent with a source address of 100.72.88.141
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 12/12/12 ms

I think the question may be related with IP SLA の基本設定   (without reply) because the confiuration are too similar, but I cannot understand the question on this post.

[MHM Cisco World]

OKI check the cisco add new command to use track with DHCP 
check it 
https://www.cisco.com/c/en/us/support/docs/routers/2900-series-integrated-services-routers/213824-configure-ip-dhcp-client-route-track-f.html

MHM

[Sakura]

Changes on configuration:

interface Cellular0/2/0
description Secondary_
ip dhcp client route track 1
ip address negotiated

ip route 0.0.0.0 0.0.0.0 Cellular0/2/0 dhcp 200
ip route 0.0.0.0 0.0.0.0 GigabitEthernet0/0/0 dhcp

After these changes, if I shut manually gi0/0/0 the Cel0/2/0 doesn't come up.

router#sh ip route track-table
router#

No route backup is shown, probably because the interface Cel0/2/0 is automatically down.

Maybe I need to force the interface to be always up to get the backup working?

[balaji.bandi]

May be run EEM script to hard reset of shut and no shut interface.

[Sakura]

I cannot understand how to do it.

I've enabled the interface forcing the route (ip route 0.0.0.0 0.0.0.0 Cellular0/2/0), but that's the only method I can find to enable it.

Trying to shut and no-shut the interface doesn't connect it.

Also, with the interface up and with an IP assigned to it, creating the route indicated before (ip route 0.0.0.0 0.0.0.0 Cellular0/2/0 dhcp 200), the command sh ip route track-table remain empty.

I understand the router disconnect the interface after a network timeout (if I remember correctly, 24 hours), and if the route doesn't request it to be up, router didn't bring it up.

Maybe the option was to create the route when the SLA fails? That's can be a solution but as I understand that's not the method.

[paul driver]

Hello
You need ONLY to track the primary default route, in your instance that is via gig0/0/0, also you need to make sure your iplsa polling only works via that same interface, so when it sla fails the same polled ip address isnt reachable via the Cellular path.

If you do not have network reachability via the backup path (including NAT) when you manually fail over then you may need to clear the nat table and test again, if this works only by clearing the nat table then you will have to implement EEM to clear the nat table dynamically upon ipsla failover

Example
ip route 8.8.8.8 255.255.255.255 gig0/0 
ip route 8.8.8.8 255.255.255.255 null0 2
ip route 0.0.0.0 0.0.0.0 gig0/0/0 dhcp 
ip route 0.0.0.0 0.0.0.0 Cellular0/2/0 20

nterface Cellular0/2/0
shut
no ip dhcp client route track 1
no shut

interface GigabitEthernet0/0/0
description ## FTTH DHCP ##
shut
ip dhcp client route track 1
ip address dhcp
no shut

Perform a manual fail-over first, and clear nat table:

Clear ip nat translation forced


EEM script  - Only apply if the above works accordingly 
event manager applet DOWN
event track 1 state down
action 1:0 cli command "enable"
action 1:1 cli command "clear ip nat translation forced"
action 1:2 cli command "end"

event manager applet UP
event track 1 state up
action 2:0 cli command "enable"
action 2:1 cli command "clear ip nat translation forced"
action 2:2 cli command "end"