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11-28-2023 05:44 AM
Hi
I have a working "ip sla" setup, following the instructions here: https://www.cisco.com/c/en/us/support/docs/ip/ip-routing/200785-ISP-Failover-with-default-routes-using-I.html and elsewhere.
The problem I've got is that in the example above the test IP is the next hop router, which is across the link being monitored. In my case, the next hop is in the same server rack so it is pointless to monitor it to determine if the line is up or not, because it always will be unless the NTE is powered off.
If I try and ping e.g. 8.8.8.8 by doing:
ping 8.8.8.8 source-interface GigabitEthernet0/0/0
or
ping 8.8.8.8 source-ip 123.0.0.1
(where 123.0.0.1 is the IP of GigabitEthernet0/0/0)
..I don't get any reply, unless i am already routing via the next-hop to Gi0/0/0. If i am routing via the 2nd ISP, NAT'ing to a different block of public IPs, then I can't access the Internet via the 1st ISP.
Just to reiterate - the NTE is in the same rack as my equipment, i.e. 123.0.0.2 is in the same rack as 123.0.0.1, so it is pointless to use 123.0.0.2 as a test IP for reachability.
Any thoughts? I feel like this is a NAT issue, but not sure how I can fix it?
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11-28-2023
06:05 AM
- last edited on
11-28-2023
04:45 PM
by
Translator
Use
Ip route 8.8.8.8 255.255.255.255 isp interface(you want to track) permanent
This command force router to use specific isp and make track correct work.
MHM
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11-28-2023
06:05 AM
- last edited on
11-28-2023
04:45 PM
by
Translator
Use
Ip route 8.8.8.8 255.255.255.255 isp interface(you want to track) permanent
This command force router to use specific isp and make track correct work.
MHM
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11-28-2023 06:10 AM
Thanks. I guess that would make that IP (Google’s DNS) inaccessible via whichever ISP is currently being used, wouldn’t it?
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11-28-2023 06:19 AM
That correct but
We usually use two dns ip 8.8.8.8 and 8.8.4.4
And also if interface down this static route is remove from rib.
So it have really some disadvantages.
MHM
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11-28-2023 09:56 AM
Thanks. I've chosen another public DNS server that we aren't using for anything else anyway.
