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ludvik
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OSPF - ethernet disable-running-check

Sat Dec 31, 2011 2:32 pm

Please, add parameter disable-running-check for ethernet interfaces. OSPF doesn't propagate route, if not link on interface.

I have "management IP" on lan side of infrastructure routers. If customer power-off self switch or CPE connected on lan side, i lose route from global route table.
Creating bridge for this problem is not good solution. Dummy interface with independent IP (/32) bad solution too.

thanks.
 
rodolfo
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Re: OSPF - ethernet disable-running-check

Sat Dec 31, 2011 3:28 pm

why does you want to propagate the route also if the client is diconnected ?
and why create a loopback bridge is a bad solution ?

thanks
rodolfo
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ludvik
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Re: OSPF - ethernet disable-running-check

Sat Dec 31, 2011 3:50 pm

because "network operation center" software is connected only to ONE IP address of this router. And this routers have two or more backbone link to core network - can not be used one of them IP address, must be uset IP which is always available from every part of the network in every situation.

But on lan side is connected only customer and if for example electric failure - route is gone ...

Another reason is unnecessary flapping OSPF.


Bridge is software solution. Use it only for one interface and just for this reason it is unduly burdensome.

And dummy addresses unnecessarily fills the route table on other routers (for example - some L3 switches have only 512 available records in the tables).

Wireless interfaces have this parameter :-) Why not ethernet?
 
rodolfo
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Re: OSPF - ethernet disable-running-check

Sun Jan 01, 2012 12:39 pm

thanks!
rodolfo
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mmmigoro
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Re: OSPF - ethernet disable-running-check

Wed Jan 04, 2012 11:56 am

OSPF is a link-state routing protocol by design. You can check definitions here http://en.wikipedia.org/wiki/Link-state ... g_protocol and here http://en.wikipedia.org/wiki/OSPF.
As stated there it is supposed to remove the route from routing table when interface is disconnected (and also it's not recommended to be used in networks topology where a big number of flapping interfaces are present).
The option disable-running-check is there for historical reasons especially for ROS which is running on x86 with cheap Ethernet cards like realtek with bad interrupts which clog up the CPU when disable-running-check=no and also is a good option for wireless interfaces for the same reasons.
Definitely it wasn't designed to be used for tricking OSPF into thinking that interface is up and so to propagate the sub-net into routing table. For this purpose use loop-back.
On CISCO there's no disable-running-check option and loop-back it's been used with success for years.
Instead use iBGP to overcome this link-state behavior.
 
ludvik
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Re: OSPF - ethernet disable-running-check

Wed Jan 04, 2012 12:41 pm

I know, what is OSPF ... But usage of Mikrotik is "SOHO" - and disable-running-check is good option for many reasons. Why not be better than Cisco?

We are small ISP, with small clouds with many PtP links - if i configure loop-back IP on every router, i have about 200 records in route table moreover. It's not very good ...

On infrastructure routers is this behavior good ... i have know if link is down ...
 
mmmigoro
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Re: OSPF - ethernet disable-running-check

Wed Jan 04, 2012 1:47 pm

As i already said, use iBGP instead, with a a central route-reflector.

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