[a-nsp] tracked static routes in EOS

[Tyler Conrad]

Hey Drew,

This is what I meant about conmon being built-in. You can chain
connectivity-monitoring for monitoring, have it syslog, and then react to
the syslog using an event handler. Gives you a lot of flexibility.

Something like this, where 10.0.0.1 is reachable on local interface via L2
transport, so we monitor it. Then depending on if it's up or not, we add or
remove a static route to 10.1.2.3/32 toward 10.0.0.1.

monitor connectivity
   no shutdown
   !
   host host1
      ip 10.0.0.1

--- Syslog output:

2026-09-11T11:54:31.144742-07:00 LAB-MGMT-48ZC2 ConnectivityMonitor:
%CONNECTIVITYMON-5-HOST_UNREACHABLE: Host host1 (10.0.0.1) is unreachable
with ICMP probes

2026-09-11T11:58:67.530900-07:00 LAB-MGMT-48ZC2 ConnectivityMonitor:
%CONNECTIVITYMON-5-HOST_REACHABLE: Host host1 (10.0.0.1) is reachable with
ICMP probes

--- Built event-handler:
event-handler Host1Down
   action bash Cli -p15 -c $'enable\n configure\n no ip route 10.1.2.3/32
10.0.0.1\n end'
   delay 0
   asynchronous
   !
   trigger on-logging
      regex "Host host1 .* is unreachable .*"

event-handler Host1Up
   action bash Cli -p15 -c $'enable\n configure\n ip route 10.1.2.3/32
10.0.0.1\n end'
   delay 0
   asynchronous
   !
   trigger on-logging
      regex "Host host1 .* is reachable .*"

Is this what you're after?

-T

On Fri, Sep 11, 2026 at 12:36 PM Drew Weaver <drew.weaver at thenap.com> wrote:

> Right but none of that is built into EOS correct?
>
>
>
> That was what the post was mostly about.
>
>
>
> Whether they had ever gone back and corrected the omission?
>
>
>
> Thanks,
>
> -Drew
>
>
>
>
>
> *From:* Tyler Conrad <Tyler at tgconrad.com>
> *Sent:* Friday, September 11, 2026 1:25 PM
> *To:* Drew Weaver <drew.weaver at thenap.com>
> *Cc:* arista-nsp at puck.nether.net
> *Subject:* Re: [a-nsp] tracked static routes in EOS
>
>
>
> Hi Drew,
>
>
>
> I've worked on a couple extensions to do this over the years, and there's
> also a built-in way.
>
>
>
> Built-in: Connectivity-monitor with an on-logging event-handler can work
> for script-less behavior.
>
> PingCheck Extension: https://github.com/arista-eosext/PingCheck
> <https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_arista-2Deosext_PingCheck&d=DwMFaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=OPufM5oSy-PFpzfoijO_w76wskMALE1o4LtA3tMGmuw&m=bPv27DsWHvJOKXO1fg-IGUnqlmv3IzCXU57K_UK6OKd83rMtLkgFxTjUGCICVrCw&s=U1Lbsb6ispBFDPisCYWxAwXksSBjf3cioxLYf8pn-ro&e=>
> - this one uses a simple ping check.
>
> SynAcktor Extension: https://github.com/etedor/synacktor
> <https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_etedor_synacktor&d=DwMFaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=OPufM5oSy-PFpzfoijO_w76wskMALE1o4LtA3tMGmuw&m=bPv27DsWHvJOKXO1fg-IGUnqlmv3IzCXU57K_UK6OKd83rMtLkgFxTjUGCICVrCw&s=49RFYRbP_3OyShNE6hz-8Ix9XOqpCVFYwaU7o1C8Uc8&e=>
> - adds flexibility to be able to monitor a tcp service and set an arbitrary
> next-hop. Useful for monitoring a path without changing the routing table.
>
>
>
> Hope this helps,
>
> -T
>
>
>
> On Fri, Sep 11, 2026 at 9:03 AM Drew Weaver via arista-nsp <
> arista-nsp at puck.nether.net> wrote:
>
> Howdy
>
>
>
> Is it true that there really is no way to do tracked static routes in EOS
> without installing a python script that you have to reinstall every time
> the switch reboots?
>
>
>
> By tracked static routes I just mean a route that withdrawals when
> something stops pinging (or another tracking mechanism) would just use BFD
> but the device on the far end of the L2 network doesn’t support it.
>
>
>
> Use case is basically just a L2 network in between the route origin and
> the destination. if the entire network goes down and the physical link
> facing the route originating device disappears then the route is withdrawn
> anyway but if only the portion on the other side of the L2 network goes
> down then you’re null routing traffic unintentionally.
>
>
>
> I’m just wondering.
>
>
>
> Thanks,
>
> -Drew
>
>
>
> --
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> arista-nsp at puck.nether.net
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>
>
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