UTM & COLT not working on a CISCO-Switch (State UP, Link DOWN)

Hey all,

we´re expericing the following strange behaviour:

2 UTM SG430 in A/P-HA are connected to a HP-Procurve 2810-24G Switch. This Switch then connects via SX-SFP to the ACCEDIAN-Router delivered from COLT with our 1 GBit WAN-Line.

So far so good, everything works.

Now we need to switch to new CISCO-Switches (9200L) as the HP is getting too old.

i connected the HP to the CISCO for transition, then moved the UTM Ports from HP to CiSCO -> everything works fine

BUT: as soon as i also move the fibre from the SFP in HP to the CISCO, the link goes up but the UTM says in dashboard "State: UP, Link: DOWN"

Odd thing is: if i connect the fibre coming from the accedian-Router to a Fibre/Copper-Converter using the same SFP and then patch this into a Gig-Port on the cisco -> the link goes up !

TCP Window scaling as in Rulez is activated. MTU on eth-interface for COLT is on 1500 ...

Any ideas where to look ?

Kind regards,


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  • Rule 7.3 did the trick. But not as expected:

    i changed the MTU-Size to 1350 as in Rule 7.3 -> after 2 seconds the state went "UP" and internet access was possible ....
    then, in an adventerous mood, i changed MTU back to 1500 -> and the connectivity STAYED up .. (with a little interuption of course)
    very odd .. Bandwidth (1GBit) is fully accessible ... so i´m happy now on the 1 side, but a litte confused on the other.