So I guess, sometimes, you learn that maybe some IP addresses wont be as reliable as you would like. Im talking about the good ole DNS servers out there that you think might last a while with good reliability. I always thought that 126.96.36.199 and 188.8.131.52 would be some good destinations for a good technology: object-tracking.
Object-tracking is really cool. I really like the results it gives. Now, if you dont know what object-tracking is, its Cisco's way of doing things like dual-ISP without a routing protocol. If ISP1 goes down, the Cisco router knows it and automatically changes the static default route to point to ISP2. That, generically, is how it works. It gets deep and very configurable, but you get the idea.
Now, with that said, I have to tell you about an experience I had. My good ole reliable 184.108.40.206 became not so reliable for the past few weeks. This caused my customer to get some very unstable results. See below, what I saw when I consoled into the Cisco 2900 router:
Dec 18 17:50:43.559: %TRACKING-5-STATE: 10 ip sla 1 reachability Down->Up
Dec 18 17:50:53.559: %TRACKING-5-STATE: 10 ip sla 1 reachability Up->Down
Dec 18 17:51:48.627: %TRACKING-5-STATE: 10 ip sla 1 reachability Down->Up
Dec 18 17:52:03.627: %TRACKING-5-STATE: 10 ip sla 1 reachability Up->Down
Dec 18 17:52:18.695: %TRACKING-5-STATE: 10 ip sla 1 reachability Down->Up
Dec 18 17:52:33.695: %TRACKING-5-STATE: 10 ip sla 1 reachability Up->Down
Dec 18 17:52:48.695: %TRACKING-5-STATE: 10 ip sla 1 reachability Down->Up
Dec 18 17:52:58.695: %TRACKING-5-STATE: 10 ip sla 1 reachability Up->Down
Dec 18 17:55:13.899: %TRACKING-5-STATE: 10 ip sla 1 reachability Down->Up
Dec 18 17:55:28.899: %TRACKING-5-STATE: 10 ip sla 1 reachability Up->Down
Notice that its UP/DOWN state changes every few seconds. Well, the network didnt like this back and forth like this, and it caused all kinds of slowness issues, etc for the customer. Needless to say, not good.
So when I saw my SLA 1, which was the one going down, as seen above, then I had to see what the destination was. See below the config. Yes, its good ole 220.127.116.11.
track 10 ip sla 1 reachability
delay down 2 up 2
track 20 ip sla 2 reachability
delay down 2 up 2
ip route 0.0.0.0 0.0.0.0 192.168.0.2 3 track 10
ip route 0.0.0.0 0.0.0.0 18.104.22.168 5 track 20
ip route 22.214.171.124 255.255.255.255 192.168.0.2 permanent
ip route 126.96.36.199 255.255.255.255 188.8.131.52 permanent
ip sla 1
icmp-echo 184.108.40.206 source-ip 192.168.0.5
ip sla schedule 1 life forever start-time now
ip sla 2
icmp-echo 220.127.116.11 source-ip 18.104.22.168
ip sla schedule 2 life forever start-time now
So, I changed it to the next hop just beyond ISP1, which is really what I should have done in the first place. I guess I shouldn't trust those two DNS servers anymore. Lesson learned.
This is the retired Shane Killen personal blog, an IT technical blog about configs and topics related to the Network and Security Engineer working with Cisco, Brocade, Check Point, and Palo Alto and Sonicwall. I hope this blog serves you well. -- May The Lord bless you and keep you. May He shine His face upon you, and bring you peace.
Monday, February 23, 2015
Cisco Object-Tracking: Select A Better "icmp-echo X.X.X.X"
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i have the up down problem also it happens every 10 secs which is the ip sla frequency i noticed that after the primary link goes down it goes to the secondary route it's normal but after 10 secs it goes to the primary again which is not working it should stay on secondary till the primary goes up againReplyDelete